U2 O3 - Anaesthesia and analgesia

Question 1

What is an ASA chart?

Answer 1

The American Society of Anesthesiologists (ASA) (2006) produced a risk assessment chart. This can be used to assess patients prior to anaesthesia.
the ASA class of a patient is based on its current health status (i.e. just before the anaesthetic) not the procedure being performed. Whilst it is slightly subjective, using this system should help to identify those patients that are considered a higher
anaesthetic risk and thus help with planning the anaesthetic and monitoring protocol. Ideally both veterinary surgeons and veterinary nurses should
perform an assessment of the patient prior to anaesthesia.

Question 2

What type of patient would be an ASA class 1?

Answer 2

A normal healthy patient

Question 3

What type of patient would be an ASA class 2?

Answer 3

Patient with mild systemic disease and no functional limitations

Question 4

What type of patient would be an ASA class 3?

Answer 4

Patient with moderate to severe systemic disease that results in some functional limitation

Question 5

What type of patient would be an ASA class 4?

Answer 5

Patient with severe systemic disease that is a constant threat to life and functionally incapacitating

Question 6

What type of patient would be an ASA class 5?

Answer 6

Moribund patient who is not expected to survive 24 hours with or without surgery

Question 7

What does E represent on an ASA status?

Answer 7

If the procedure is an emergency, the physical status is followed by an ‘E’ (for example, ‘4E’)

Question 8

Who should monitor a patient with a high ASA status?

Answer 8

The ASA score of a patient might be a consideration when deciding who should monitor the anaesthetic- ideally the nurse monitoring the high risk patient should have enough experience to recognise and rapidly respond to complications such as hypotension and arrythmias i.e. ventricular premature contractions (VPC), ventricular tachycardia etc. (Zeltzman, 2016). However, it is equally important to realise that just
because a patient has a low ASA, a safe anaesthetic is not guaranteed.

Question 9

An emergency patient is unlikely to have an anaesthetic procedure postponed until the patient has a lower ASA status, What should be done in this case?

Answer 9

In emergency and critical care (ECC), there will be many patients who are in ASA class 4 and 5 +/- E. Because of the nature of the patient’s condition e.g. gastric dilation and volvulus (GDV), it is unlikely the anaesthetic procedure can be postponed until the patient has a lower ASA status. Therefore, an anaesthetic risk assessment must be made for each patient and steps taken to minimise these risks
as much as possible. Optimal patient stabilisation should be achieved prior to anaesthesia (e.g. oxygen administration and intravenous fluid therapy (IVFT) etc.).
Intravenous access should be established in the emergency patient before anaesthesia is induced, to allow for the prompt administration of emergency
medications should the need arise. An emergency patient may not have been starved for an appropriate time prior to induction, putting them at increased risk of
regurgitation and possible aspiration- anticipating this and being ready to manage it is far more likely to be effective than dealing with a crisis if it arises. The team
should be prepared for this and have equipment, such as suction, available in case of this eventuality.
Efforts should be made to correct any problems prior to anaesthesia, where possible.
For example, hypovolaemic patients should be appropriately fluid resuscitated prior to induction- although as there may be ongoing problems e.g. internal bleeding the fluid resuscitation may only be temporary and surgery will still be required, as soon as possible.

Question 10

What 5 haemodynamic instabilities are most commonly seen in emergency patients?

Answer 10

Haemodynamic instability

a. Hypovolaemia
b. Vasodilation
c. Arrhythmias
d. Decreased renal perfusion
e. Hypotension

Question 11

What 3 conditions are commonly seen in patients with respiratory compromise?

Answer 11

2. Respiratory compromise
   a. Pulmonary parenchymal disease
   b. Pleural space disease
   c. Upper airway disease

Question 12

What are the main problems relating to the haemodynamic, respiratory and neurological systems that are encountered in emergency patients?

Answer 12

Haemodynamic instability

a. Hypovolaemia
b. Vasodilation
c. Arrhythmias
d. Decreased renal perfusion
e. Hypotension

2. Respiratory compromise
   a. Pulmonary parenchymal disease
   b. Pleural space disease
   c. Upper airway disease
3. Neurological compromise/injury
4. Anaemia
5. Electrolyte abnormalities
6. Acid-base derangements
7. Gastrointestinal disease
8. Pregnancy associated changes

Question 13

If a patient has septic peritonitis and it is not possible to stabilise the patient hemodynamically due to vasoplegia, prior to surgery - what may need to be done?

Answer 13

This should be addressed prior to induction of anaesthesia, where possible, focussing on trying to resolve hypovolaemia and/ or hypotension. Remember it does not take long to give a fluid bolus (isotonic crystalloids, hypertonic saline (HTS) or colloids depending on the situation). However, in a patient with septic peritonitis and widespread vasodilation/ vasoplegia, for example, it may not be possible to stabilise the patient haemodynamically until the underlying problem is addressed. In this situation, rapid surgical intervention may be the most effective means of making the patient stable

Question 14

How much acute blood loss in a patient would a blood transfusion need to be considered?

Answer 14

A packed red cell (pRBC) transfusion, or whole blood transfusion where pRBCs are not available, should be considered for any patient with more than 10ml/kg blood loss.

Question 15

What type of monitoring equipment is important to use in an emergency patient?

Answer 15

Relevant monitoring equipment should be available and attached prior to induction
o pulse oximeter
o blood pressure
o capnograph
o ECG
o temperature monitoring

Question 16

What premedicant drugs should be avoided in a high risk emergency patient?

Answer 16

There are some drugs that are avoided/ used with caution in high risk patients
e.g.
– acepromazine
– medetomidine

Question 17

What anaesthetic induction technique should be used in a high risk emergency patient?

Answer 17

• A balanced anaesthetic induction technique should be used e.g.
– opioid/ benzodiazepine
– diazepam/ ketamine
– minimal amounts of induction agent e.g. propofol/ alfaxalone

Question 18

What is the aim of balanced anaesthesia in a emergency patient?

Answer 18

The aim of balanced anaesthesia is to minimise the risk to the patient and maximise its comfort and safety

Question 19

What is the aim of a co-induction protocol?

Answer 19

The aim is to use a combination of drugs in small volumes to maximise the benefit of each and reduce the amount of side effects associated with one large volume single agent.

Question 20

Why is the order in which drugs are given relevant in a co-induction protocol?

Answer 20

The order in which drugs are given can also be
relevant. An example situation would be a patient needing an emergency laparotomy. For pain management, a pure opioid could be administered intravenously. Once this has reached peak plasma levels, and preparations have been made for anaesthetic induction, a calculated dose of a benzodiazepine could then be administered. This results in less induction agent being required
which is beneficial as it minimises undesirable side effects. Pain management is a key factor in smooth anaesthesia and reducing the amount of volatile
agent required. Additional techniques such as infiltration of local anaesthetic and local anaesthetic blocks may also be of benefit in pain management
during the anaesthetic

Question 21

What respiratory emergency will require immediate anaesthesia?

Answer 21

Some respiratory emergencies may require immediate anaesthesia e.g.
complete upper airway obstruction in a brachycephalic patient or a pharyngeal foreign body. It is far better to act promptly in these situations, and secure an airway, rather than wait and risk the patient deteriorating further.
Induction and intubation should be rapid if there is upper airway disease and the airway needs to be secured

Question 22

In a patient with a closed pneumothorax, what is it important to avoid during induction and anaesthesia?

Answer 22

In a patient with a closed pneumothorax, intermittent positive pressure ventilation (IPPV) should be avoided due to changes in intra-thoracic pressures, unless absolutely necessary. A patient could develop barotrauma if IPPV is instigated. It is even more important in this patient that slow induction
of anaesthesia is performed to avoid a period of apnoea. If, for example, propofol is administered too quickly apnoea will develop. The patient will then
have to be intermittently ventilated and the positive pressure within the lungs may cause worsening of the pneumothorax

Question 23

What is the emergency management of pleural space disease prior to induction of anaesthesia?

Answer 23

Emergency management of pleural space disease is indicated prior to induction to of anaesthesia (i.e. oxygenation and thoracocentesis)

Question 24

What equipment should be prepared prior to a respiratory emergency?

Answer 24

• It is important to be prepared.
o Ensure all the required equipment is available e.g.
▪ laryngoscope
▪ pre-tied tubes
▪ monitoring equipment
o Clip and prep the surgical area prior to induction of anaesthesia, if
possible, (and attach monitoring equipment) e.g. for placement of a
chest tube
o Ensure a surgical pack is available, for performing an emergency
tracheostomy, if upper airway obstruction is a possibility.

Question 25

What monitoring equipment should be attached prior to induction of a respiratory emergency?

Answer 25

``` Have the necessary monitoring available and attached prior to induction o pulse oximeter o blood pressure o capnograph o ECG o thermometer ```

Question 26

Why is it important that brachycephalic patients are pre-oxygenated prior to anaesthesia?

Answer 26

Brachycephalic patients will commonly have a much lower than normal SpO2 on room air. Consequently, the timeframe for them to become hypoxic is much more rapid than with a patient that has a normal SpO2 when breathing room air.

Question 27

What percentage of cardiac output does the brain normally receive?

Answer 27

Cerebral perfusion – the brain normally receives ~ 15-20 % of the cardiac output and it is essential that this is maintained following any head injury

Question 28

How can cerebral blood flow be estimated?

Answer 28

Cerebral blood flow can be estimated by working out the cerebral perfusion pressure (CPP) = Mean Arterial Blood Pressure (MAP) – Intracranial Pressure (ICP).

Question 29

What is a cushings reflex a combination of?

Answer 29

Cushing’s reflex is the combination of increased blood pressure and bradycardia

Question 30

What could a decrease in blood pressure in a patient with a head injury and potential increased intracranial pressure lead to?

Answer 30

Any decrease in MAP in a patient with a head injury, and potential increased ICP, could lead to decreased blood flow to the brain. Thus, all efforts should be made to prevent any further increase in ICP and decrease in MAP

Question 31

Why is it important to avoid hypercapnia in a patient with known or suspected increased cranial pressure?

Answer 31

It is also important to avoid hypercapnia as this causes vasodilation and potentially further increases ICP by increasing cerebral perfusion; hypocapnia causes vasoconstriction- thus decreasing cerebral blood flow and causing ischaemia.

Question 32

Why is it important to avoid hypoxaemia in a patient with known or suspected increased cranial pressure?

Answer 32

Hypoxaemia has the same effect as hypercapnia- it causes vasodilation and so can lead to increased ICP

Question 33

What are the nursing considerations in a patient with head trauma that requires an anaesthetic?

Answer 33

a patient with head trauma that requires an anaesthetic must be carefully monitored and ventilated to maintain ETCO2 within normal levels. • Avoid increasing intracranial pressure (ICP) further o (care re positioning- head and neck extended and elevated) • Maintain adequate mean arterial pressure • Avoid hypoxia (monitor SpO2) • Avoid hypercapnia (monitor ETCO2) • Avoid compression of jugular veins • Monitor ECG • Avoid any interventions that might cause vomiting, coughing or sneezing- all can increase ICP • Avoid anything that increases cerebral metabolic rate (CMR) – overheating, excitability, pain should all be considered and managed as required. • Aim to maintain normothermia. Permissive hypothermia may be incorporated in the management of a patient with traumatic brain injury to reduce CMR. A temperature of 37-37.5 ˚C is acceptable.

Question 34

What drugs should be avoided in a patient with increased cranial pressure and why?

Answer 34

Drugs to avoid * o Acepromazine (cerebral vasodilation) o Morphine (causes vomiting) o * Ketamine (increased ICP) N.B. current reviews in human literature suggest this may be less of a concern than previously thought. Low dose ketamine may be administered by some clinicians to patients with traumatic brain injury. o Possibly isoflurane (cerebral vasodilation)- although unlikely to be possible if inhalational anaesthesia is required. However, total intravenous anaesthesia (TIVA) protocols may be considered for these patients instead

Question 35

What is it important to be aware of when monitoring an SPO2 in an anaemic patient?

Answer 35

A decreased haematocrit means there is less oxygen carrying capacity- it is important to be aware of this when recording SpO2 with pulse oximeter. Whilst those RBC that are present may be adequately saturated with oxygen, meaning the SpO2 reading will be normal, if there are less RBCs circulating, the patient will be hypoxaemic

Question 36

In a patient with blood loss what should happen ideally before commencing anaesthesia?

Answer 36

In a patient with blood loss, intravascular blood volume should ideally be as close to normal as possible before commencing anaesthesia

Question 37

What are the nursing considerations when an anaemic patient requires an anaesthetic?

Answer 37

Anaemia, causes, diagnosis and treatment and blood transfusion will be covered in more detail in Unit 3 Outcome3 • In a patient with blood loss, intravascular blood volume should ideally be as close to normal as possible before commencing anaesthesia (Gianotti and Steagall, 2018). • Calculate the packed cell volume (PCV) and monitor it alongside total protein (TP). However, in a patient with acute haemorrhage, it is important to be aware the PCV may remain normal for some time due to splenic contraction. Careful ongoing monitoring is indicated if there is any suspicion of blood loss. • If there is abdominal bleeding, the PCV of the abdominal blood can be compared with the circulating PCV (Jasani, 2015) • A decreased haematocrit means there is less oxygen carrying capacity- it is important to be aware of this when recording SpO2 with pulse oximeter. Whilst those RBC that are present may be adequately saturated with oxygen, meaning the SpO2 reading will be normal, if there are less RBCs circulating, the patient will be hypoxaemic. • Transfusion of blood products may be considered prior to induction, depending on reason for anaemia- more likely in acute blood loss. • Identify the patient’s blood type and assess availability of blood products if there is a potential need for these during or after the surgical procedure. • An autotransfusion may be a consideration in a patient with abdominal haemorrhage. • PCV / TP will need to be measured intra-operatively and post-operatively.

Question 38

What electrolyte abnormalities can cause sudden and fatal arrhythmias?

Answer 38

Some electrolyte abnormalities, especially potassium and calcium, can cause sudden and fatal arrythmias, due to the effects they have on cardiac muscle, if not promptly recognised and managed. The more serious the electrolyte abnormality is, the greater the potential cardiac effects.

Question 39

What can severe hypokalaemia cause?

Answer 39

Severe hypokalaemia can cause ventricular arrhythmias

Question 40

What can severe hyperkalaemia cause?

Answer 40

Severe hyperkalaemia can cause bradycardia and cardiac arrest.

Question 41

What treatment options may be used in the management of a patient with hyperkalemia?

Answer 41

The following treatment options may be used in the management of a patient with hyperkalaemia - o intravenous fluid therapy to dilute the serum potassium o calcium gluconate- this does not reduce serum potassium but helps to stabilise cardiac membranes and protect heart muscle cells. o insulin and dextrose – drives potassium intracellularly o intravenous fluids

Question 42

What are the several causes for metabolic acidosis?

Answer 42

Metabolic acidosis is common in ECC patients. There are several causes of metabolic acidosis (e.g. increased lactate, diabetic ketoacidosis)

Question 43

What is the most common cause of metabolic acidosis and what can be done to help correct this?

Answer 43

The most common cause is when decreased perfusion results in anaerobic respiration and lactate accumulation. Resuscitative intravenous fluid therapy, prior to anaesthesia, will help to address the decreased perfusion.

Question 44

What is the most common cause of metabolic alkalosis? and what is the treatment for this?

Answer 44

This is less common than metabolic acidosis but is most likely to be a hypochloraemic metabolic alkalosis secondary to a high gastrointestinal or pyloric outflow obstruction (loss of HCl with vomiting) ▪ 0.9% NaCl may be administered to manage the alkalosis as is it an acidifying solution

Question 45

What is an accumulation of CO2 (hypercapnia) usually secondary to with respiratory acidosis?

Answer 45

Accumulation of CO2 (hypercapnia) is usually secondary to inadequate ventilation (hypoventilation) or sometimes ventilation– perfusion mismatch.

Question 46

What are the aims of premedication?

Answer 46

Depending on the anaesthetic regime being used, the aims of premedication include some or all the following- ➢ reduce anxiety and stress ➢ pre-emptive analgesia ➢ calm induction of anaesthesia ➢ decreased induction agent/ volatile agent and corresponding side-effects ➢ smooth recovery

Question 47

What drug class is acepromazine in and what physiological effects does it have?

Answer 47

Acepromazine maleate is a phenothiazine drug that works by antagonising dopamine receptors in the central nervous system

Question 48

What physical effects can acepromazine have on a patient?

Answer 48

It is used in ‘routine’ anaesthesia as a premedicant and produces tranquillisation, with sedation appearing at higher doses (Flaherty, 2009). Acepromazine also has antiarrhythmic, antihistamine, antiemetic and smooth muscle spasmolytic effects

Question 49

What combinational effects does acepromazine have if added with buprenorphine?

Answer 49

The addition of an opioid, such as buprenorphine, creates a neuroleptanalgesic combination, which potentiates the sedative effects and makes them more reliable.

Question 50

What is the major side effect associated with acepromazine and why is it not commonly used in an emergency?

Answer 50

The major side-effect of acepromazine is vasodilation which can cause hypotension. It also has a long duration of action, can cause hypothermia due to peripheral vasodilation and does not have a reversal agent. Acepromazine is not commonly used in emergency cases, due to its vasodilatory/ hypotensive effect, as many patients have cardiovascular compromise and hypotension

Question 51

Why is it useful to combine acepromazine with an opioid?

Answer 51

This is also useful as the combination allows the reduction of the acepromazine dosage and so minimises some of its side-effects- dose sparing effect

Question 52

Why is acepromazine useful in animals with dynamic upper airway disease?

Answer 52

It is, however, a useful sedative in haemodynamically stable patients that have dynamic upper airway disease. Reducing the inspiratory effort in dogs with laryngeal paralysis, often reduces the dynamic obstruction thus helping the dog to ventilate more efficiently, usually.

Question 53

Why should acepromazine be avoided in brachycephalic breeds and in particular which breed?

Answer 53

Because of its hypotensive effects, acepromazine may cause syncope in brachycephalic breeds, such as the Boxer. It is usually administered at a lower dose in brachycephalic and giant breed dogs where the hypotensive effect and length of action can be marked. There is minimal evidence to support previous guidance that acepromazine should be avoided in dogs with epilepsy

Question 54

Why is acepromazine useful when managing feline patients with urethral obstruction?

Answer 54

Due to its effect on smooth muscle, it can be useful when managing feline patients with urethral obstruction. However as outlined above, it usually paired with a full opioid or a partial agonist to reduce the potential behavioural side effect of excitability.

Question 55

what use can benzodiazepines have in emergency patients?

Answer 55

Benzodiazepines can be used in emergency patients for several reasons- they are anxiolytic in some patients; have minimal effects on the cardiovascular and respiratory system; cause muscle relaxation and have an anticonvulsant effect

Question 56

What unwanted effects can benzodiazepines have on healthy patients?

Answer 56

In healthy patients, however, rather than an anxiolytic effect they can often cause excitement; and as they reduce inhibition, administration can cause aggression and fear-based behaviours to worsen.

Question 57

What type of emergency patients often receive benzodiazepines?

Answer 57

The anti-convulsive effects of benzodiazepines mean they are often the first choice of treatment in emergency patients presenting with seizures e.g. status epilepticus.

Question 58

What are the two most common types of benzodiazepines used in practice?

Answer 58

The two commonly used benzodiazepines in practice are diazepam and midazolam.

Question 59

Benzodiazepines work by enhancing the effect of....?

Answer 59

Benzodiazepines work by enhancing the effect of the neurotransmitter gamma amino butyric acid (GABA) at the GABA receptor

Question 60

How does midazolam compare to diazepam?

Answer 60

Midazolam is more potent than diazepam, with a more rapid onset and shorter duration of action- it is, however, unreliable by itself as a sedative so is often combined with other agents

Question 61

What route is preferred when administering diazepam?

Answer 61

Diazepam is painful if administered by the intramuscular route, so the intravenous route is preferred, if it is being injected. Many preparations of diazepam are not water soluble and can induce muscle necrosis if given IM. The suspension preparation of injectable diazepam is preferred as it is less likely to cause phlebitis Because Midazolam is water soluble it does not have these administration associated side-effects. Diazepam can also be administered per rectum in seizuring patients, but the rate of onset and efficacy is variable. N.B. recent research has demonstrated that midazolam can be administered by the intranasal route in seizuring dogs

Question 62

Why are opioids typically used for animals undergoing elective procedures?

Answer 62

Opioids are typically used in healthy patients undergoing elective procedures (e.g. castration) for their sedative and pre-emptive analgesic effects.

Question 63

What are some examples of opioids used in veterinary practice?

Answer 63

Examples of opioids used in veterinary medicine in the UK include methadone, pethidine, morphine, fentanyl, buprenorphine and butorphanol.

Question 64

What drug class is medetomidine, Xylazine and dexmeditomidine?

Answer 64

Alpha-2 adrenergic agonists

Question 65

What are the physiological and physical effects of Alpha-2 adrenergic agonists?

Answer 65

They bind to alpha-2 receptors, within the central and peripheral nervous system, so inhibiting the release of noradrenaline/ norepinephrine thus causing sedation, muscle relaxation and some analgesia.

Question 66

What effect does alpha-2 adrenergic agonists produce?

Answer 66

Alpha-2 adrenergic agonists (alpha-2s) produce profound, dose dependent sedation. The duration of sedation is also dose dependent. They produce excellent muscle relaxation, have minimal effect on the respiratory system

Question 67

What is a great advantage that alpha - 2 adrenergic have?

Answer 67

the advantage of having a specific reversal agent (atipamezole)

Question 68

What is the main disadvantage of alpha-2 adrenergic drugs and why are they not commonly used in emergency patients?

Answer 68

Their main disadvantage is the profound cardiovascular depression they cause- initial hypertension, due to peripheral vasoconstriction, followed rapidly by bradycardia and hypotension. This combined with respiratory depression side-effects can lead to significant tissue hypoxia in non-ventilated patients; and potentially serious hypotensive effects in cardiovascularly compromised patients.

Question 69

What should be considered when administering an alpha-2 adrenergic in a diabetic patient?

Answer 69

Alpha-2s also suppresses insulin release which is an important consideration in diabetic patients; they also suppress antidiuretic hormone release creating diuresis.

Question 70

Can alpha-2 adrenergic be given to pregnant animals?

Answer 70

They should not be administered to pregnant patients due to the profound vasoconstriction leading to decreased blood supply to the foetuses. Some alpha-2s also cause emesis.

Question 71

What are the two main anticholinergic and anti-muscarinic drugs used in practice?

Answer 71

The two main anticholinergic or anti-muscarinic drugs in use are atropine sulphate and glycopyrrolate

Question 72

What are the three main reasons anticholinergics are used in practice?

Answer 72

They do not tend to be used routinely now but are reserved for specific situations where their use is likely to be of benefit (Flaherty, 2009) e.g. to relieve vagally induced bradycardia; and possibly to reduce oral and respiratory tract secretions, Atropine could be administered to a patient with cardiopulmonary arrest which is related to increased vagal tone and associated asystole or pulseless electrical activity

Question 73

Why are brachycephalic breeds more at risk of bradycardia during anaesthesia or surgery?

Answer 73

Brachycephalic dogs often have a high resting vagal tone which could lead to bradycardia during anaesthesia; surgical procedures involving the eye and larynx are also associated with increased vagal tone so potential for bradycardia during anaesthesia

Question 74

What negative effect do anticholinergic drugs when they reduce secretions?

Answer 74

However, whilst anticholinergic agents do reduce the volume of mucous and other secretions, the consistency is much thicker, which could cause blockage of airways/ the ET tube

Question 75

What are the unwanted effects of anticholinergics?

Answer 75

Anticholinergics can be used in the treatment of atrioventricular heart block. However, their potential side-effects include tachycardia and other serious arrhythmias because they facilitate transmission of electrical signals through the AV node. They also increase myocardial oxygen consumption, because of the increased heart rate they cause. Therefore, their use in patients with cardiovascular compromise, other than bradycardia, is not advisable. Because they cause mydriasis, they should not be used in patients with glaucoma

Question 76

What are the side effects of NSAIDS and why are they not commonly used in ECC patients?

Answer 76

They can cause gastric ulceration, decreased renal perfusion and decreased platelet activity/ prolonged bleeding. As ECC patients are often hypovolaemic, hypotensive, dehydrated and/or have renal compromise, NSAIDs should not be routinely given prior to induction of anaesthesia. Side effects include renal damage, disorders of haemostasis and gastric ulceration

Question 77

What is TIVA?

Answer 77

total intravenous anaesthesia TIVA

Question 78

What is propofol and what is it used for?

Answer 78

Propofol is a short-acting hypnotic agent that can be used for induction and maintenance of anaesthesia either by incremental doses or continuous rate infusion (CRI) It is phenol based, lipid-soluble compound which is much less irritant, if injected peri-venously, than its predecessor, thiopentone.

Question 79

How quickly does propofol take effect and how long does it last in cats?

Answer 79

Propofol has a rapid onset of action and short duration although it can last up to 20 minutes in cats

Question 80

How long does the preservative free version of propofol last?

Answer 80

The preservative free version must be used and discarded on the same day as opening.

Question 81

How long does the multi use vial of propofol last?

Answer 81

The multi-use vial preparation of propofol, with the preservative benzyl alcohol, is licenced for multi-use and must be discarded within 28 days of opening

Question 82

Which propofol preparation is most suitable for TIVA?

Answer 82

It is important to be aware of which preparation of propofol is available, as propofol with preservative is not suitable for TIVA / CRI (e.g. in the emergency management of a seizuring patient). Propofol (without the preservative) may be used for total intravenous anaesthesia (TIVA) as bolus injections or CRI. Propofol (with preservative) should not be used to maintain anaesthesia for any longer than 30 minutes. Because propofol can cause dose-dependent bradycardia, vasodilatation, and respiratory depression it should be injected slowly to effect, over 90 seconds.

Question 83

What is the recovery usually like from a propofol induction and why? What breed can this effect?

Answer 83

Recovery from propofol anaesthesia is generally rapid, because of fast metabolism and some fat redistribution. However, recovery may be slower in sighthounds due to their lack of fat. Repeated doses or continuous infusion do not appear to cause hangover effects

Question 84

Why is propofol acceptable to use in patients with increased intracranial pressure?

Answer 84

because it reduces cerebral blood flow it can be used | in a patient with increased intracranial pressure.

Question 85

What are the main disadvantages of using propofol?

Answer 85

The main potential disadvantages of propofol are marked cardiovascular and respiratory depression. It also does not have any analgesic properties. Propofol has also been associated with some muscle tremors, rigidity and twitching. When used for prolonged periods, as a constant rate infusion, patients will frequently have tremors and rigidity that can be easily mistaken for seizure activity

Question 86

Why should repeated lengthy anaesthetics using propofol in cats be avoided?

Answer 86

Repeated or lengthy anaesthetics using propofol in cats have resulted in damage to red blood cells (Heinz body formation)

Question 87

What is alfaxalone and what mode of action does it have?

Answer 87

Alfaxalone is a clear, colourless preparation of a neuroactive steroid molecule which binds to GABA cell surface receptors, and acts by affecting chloride ion transport within the neuronal cell membrane.

Question 88

What are the routes of administration for alfaxalone and how slowly should it be administered intravenously?

Answer 88

Alfaxalone should be administered slowly IV over 60 - 90 seconds to reduce the likelihood of apnoea – it can also be given as a CRI or used for TIVA (see section 2.3.3.6); it can also be administered alone by the IM route in cats or combined with other agents e.g. butorphanol

Question 89

What is the main advantage of using alfaxalone?

Answer 89

The main advantage of alfaxalone is that the half-life is relatively short in both dogs and cats. Alone, it has poor analgesic effects. Like propofol, alfaxalone has a rapid onset of action and short duration. It has similar properties to propofol but is reported to have few cardiovascular effects if given at the recommended dose, However, it can be associated with excitable recoveries.

Question 90

Are benzodiazepines and ketamine in combination safe to use in ECC patients?

Answer 90

This combination is generally considered relatively safe for inducing anaesthesia in critically ill patients, although tends to be used most often in feline. Ketamine exerts a positive inotropic effect on the myocardium, increases the heart rate and therefore the cardiac output.patients

Question 91

What effect does ketamine have on the heart?

Answer 91

Ketamine exerts a positive inotropic effect on the myocardium, increases the heart rate and therefore the cardiac output.

Question 92

What heart condition is ketamine generally not recommended and why?

Answer 92

Ketamine combinations are generally not recommended in patients with hypertrophic cardiomyopathy; however, the use of a benzodiazepine produces a reduction in cardiovascular side-effects. Ketamine exerts a positive inotropic effect on the myocardium, increases the heart rate and therefore the cardiac output.

Question 93

Why is ketamine not suitable for patients with head trauma or glaucoma?

Answer 93

Ketamine also increases intracranial and intraocular pressure and so should not be used in cases of pre-existing increased intracranial or intraocular pressure or head trauma

Question 94

How are volatile anaesthetic gases categorised?

Answer 94

Volatile anaesthetic gases are categorised according to their blood: gas solubility, which determines how fast they induce anaesthesia and allow recovery from anaesthesia; and on their minimum alveolar concentration (MAC) values.

Question 95

How does the gas solubility of a volatile agent and minimum alveolar concentration determine how potent it is?

Answer 95

It therefore follows that the lower the blood: gas solubility the faster the agent will work; and the lower the MAC, the more potent it is.

Question 96

The effect of a volatile agent is dependent on what 7 different factors?

Answer 96

The effect of a volatile (gaseous) anaesthetic agent is dependent on several factors I. the percentage concentration of the volatile anaesthetic delivered in oxygen II. the respiration rate and depth of the patient, which affects the alveolar ventilation and therefore amount of inhalant agent received III. the solubility of the anaesthetic in the blood stream, which determines how long it remains in the bloodstream. Lower solubility volatile anaesthetics have a more rapid onset. IV. the potency of the volatile agent (minimum alveolar concentration- mac). With more potent agents, the anaesthetic can be maintained at a lower setting. V. cardiac output which will determine how rapidly the anaesthetic agent is transported to the CNS VI. whether the patient has lung disease or condition affecting the respiratory tract. These may cause an unpredictable anaesthetic due to impaired ventilation and the challenge of getting sufficient inhalant gas into the blood stream.

Question 97

What special care should be taken when providing IPPV to a patients in regards to inhalation uptake?

Answer 97

Special care should be taken when providing intermittent positive pressure ventilation (IPPV) or positive end-expiratory pressure (PEEP) ventilation, using an inhalant agent, to a patient during anaesthesia. As the ventilations are delivered to the patient, uptake of the anaesthetic agent is greater than if they are breathing spontaneously. Therefore, it is advisable to use lower percentages on the vaporiser than normal to minimise the risk of inhalant agent overdose.

Question 98

What effect does isoflurane have on the heart?

Answer 98

Isoflurane has a direct negative inotropic effect on the myocardium so reducing contractility and stroke volume. However, cardiac output is generally maintained due to an increase in heart rate. Isoflurane does however cause marked peripheral vasodilation and will lead to dose-dependent hypotension, as with all volatile agents.

Question 99

What drug class is isoflurane in and what is the gas solubility coefficient and MAC?

Answer 99

This is a halogenated ether compound and is currently licensed for use in dogs and cats in the UK. It has a blood: gas solubility coefficient of 1.5 and a MAC of 1.28%

Question 100

What effect does isoflurane have on the respiratory system?

Answer 100

It can cause respiratory depression; however, the | inspirations are usually deeper.

Question 101

How does isoflurane compare to sevoflurane?

Answer 101

Isoflurane does not sensitise the heart to catecholamines and so arrhythmias are less common than with halothane. induction and recovery from anaesthesia is likely to be quicker than with isoflurane; however, it is less potent and so a higher concentration of anaesthetic agent will be required to induce and maintain anaesthesia The cardiovascular and respiratory side-effects are like those of isoflurane. As it is less blood soluble than halothane and isoflurane, it provides rapid induction and recovery. If considered necessary and appropriate, dogs and cats could theoretically be ‘face-masked down’ and induced with 100% oxygen and 6-8% sevoflurane. Being less irritant to mucous membranes than isoflurane, sevoflurane may be better tolerated for this purpose

Question 102

What drug class is Sevoflurane in and what is the gas solubility coefficient and MAC?

Answer 102

This is a halogenated ether compound – licensed for use in dogs and cats in the UK. It has a blood: gas solubility coefficient of 0.68 and a MAC of 2.36%.

Question 103

What is nitrous oxide, how is it used? and what are the main benefits of using it?

Answer 103

This gas is a very weak anaesthetic agent i.e. it is not potent which means it is not suitable as the sole anaesthetic maintenance agent. However, it can be used with other anaesthetic agents. The main benefits of nitrous oxide are the second gas effect and its limited analgesic action. If used, nitrous oxide needs to be delivered in high concentrations (>50%) but not so high that it induces hypoxia (<70%). It is very poorly soluble in blood (blood: gas coefficient of 0.47) which means it has rapid uptake, distribution and elimination and no significant liver metabolism.

Question 104

Why are lower doses of volatile agent required when using nitrous oxide?

Answer 104

Rapid uptake of nitrous oxide at induction also results in high levels of oxygen and the other volatile agent reaching the alveoli i.e. In turn, more oxygen and volatile agent reach the bloodstream i.e. nitrous oxide increases the alveolar: blood gradient of the other volatile anaesthetic gas and so increases its the rate of uptake. This means that lower dosages of the other volatile agent are required i.e. a lower vapouriser setting, thus minimising cardiopulmonary and respiratory depression.

Question 105

What is the main disadvantage of using nitroud oxide?

Answer 105

The main disadvantage of nitrous oxide is when facing the reverse situation- when anaesthesia is terminated nitrous oxide rapidly enters the alveolar space from the blood stream, effectively displacing oxygen which can lead to hypoxia (referred to as diffusion hypoxia). Therefore, it is essential to ventilate patients with 100% oxygen for 5-10 minutes after the nitrous oxide is turned off. Another disadvantage of nitrous oxide is that is rapidly moves into any air-filled viscus, and as such should be avoided in gastrointestinal or thoracic surgery.

Question 106

What are the two main breathing anaesthetic circuit systems classified as?

Answer 106

In the simplest terms, the two main breathing systems used in the UK are classified as non-rebreathing and rebreathing

Question 107

What determines what a non-rebreathing system is?(anaesthetic circuit)

Answer 107

With a non-rebreathing system (e.g. Bain, Lack, T-Piece, Magill), exhaled carbon dioxide is eliminated to a waste or exhaust system

Question 108

How do you calculate a patient's minute volume?

Answer 108

The minute respiratory volume is approximately 200-250ml/kg/min for dogs and cats (respiratory rate x tidal volume)

Question 109

How do you calculate a patient's oxygen flow rate?

Answer 109

The oxygen flow rate for a patient should be the | minute volume x circuit factor.

Question 110

What is a patients gas flow rate dependent on?

Answer 110

The gas flow rate is dependent on the | circuit chosen and its circuit factor - and the patients respiratory rate

Question 111

What determines what a rebreathing system is?(anaesthetic circuit)

Answer 111

With a rebreathing system (circle, to-and-fro), the same gas is rebreathed several times by the patient and the exhaled carbon dioxide is absorbed by a soda-lime absorber (Johnson, 2009). For a rebreathing system to be used it is essential that the soda-lime absorber is used correctly and changed as required. If there is any doubt about the freshness of the soda-lime, it is safer to change it

Question 112

When should soda lime in a rebreathing circuit be changed?

Answer 112

it should be changed if more than 50% of the soda-lime has changed colour.

Question 113

How does the gas flow rate vary when using a non-rebreathing and rebreathing circuit?

Answer 113

The gas flow rate for a rebreathing system is much lower than for a non-rebreathing system.

Question 114

What 3 different ways can a rebreathing system be used?

Answer 114

Depending on the gas flow rate provided to the patient, a non-rebreathing system can be considered closed, semi-closed or low flow anaesthesia

Question 115

How much fresh gas is required to meet the cellular metabolic requirement?

Answer 115

The amount of fresh gas required to meet the cellular metabolic requirement is ~ 10 ml/ kg/ minute

Question 116

Generally what should the initial gas flow rate on an anaesthetic be and what can this be decreased to?

Answer 116

Generally, the initial gas flow delivery rate should be ~ 100 ml/ kg/ minute. Once the patient is stable this can be decreased to 10 ml/kg/ minute or 0.5-1l/ minute for a patient less than 50kg.

Question 117

What anaesthetic circuit can be used as a rebreathing and non-rebreathing system?

Answer 117

The Humphrey-Ade system is a hybrid system which can be used as a rebreathing system, with soda-lime absorption, and a non-rebreathing system as required and depending on the patient

Question 118

What are some of the advantages of non-rebreathing system over rebreathing systems?

Answer 118

Some advantages of the non-rebreathing systems over rebreathing systems include I. lower airway resistance (and so more useful for smaller patients) II. less bulky equipment III. the inspired volatile agent content is almost equal to that set on the vaporiser IV. the inspired volatile content can be changed rapidly to alter the depth of the patient’s anaesthetic V. a period of increased oxygen delivery at the beginning and end of the anaesthetic (denitrogenation) is not required

Question 119

What are some of the advantages of rebreathing systems over non-rebreathing systems?

Answer 119

Some advantages of the rebreathing systems over the non-rebreathing systems include - I. lower gas flow rates are required and so more efficient II. less loss of heat and moisture III. less environmental pollution

Question 120

What is the circuit factor and fresh gas flow rate for an ayres T piece?

Answer 120

Circuit factor 2.5-3 500- 600 ml/kg/minute ~ 2.5 -3 x MRV

Question 121

What is the circuit factor and fresh gas flow rate for a bain (Modified) circuit?

Answer 121

300-400 ml/kg/minute 1.5-2 x MRV (previously 2-3 times MRV)

Question 122

What is the circuit factor and fresh gas flow rate for a Magill?

Answer 122

180- 200ml/kg/minute | ~ 08-1 x MRV

Question 123

What is the circuit factor and fresh gas flow rate for a mini lack?

Answer 123

200ml/kg/minute | 1 x MRV

Question 124

What is the circuit factor and fresh gas flow rate for a lack?

Answer 124

180-200ml/kg/minute | ~ 0.8- 1 x MRV

Question 125

What is the circuit factor and fresh gas flow rate for a Humphrey ADE?

Answer 125

100-150 ml/kg/minute 0.5-0.75 x MRV N.B. lower flow rates than this can be used if rebreathing

Question 126

What is the fresh gas flow rate for a circle?

Answer 126

10-100ml/kg/minute

Question 127

What is the fresh gas flow rate for a to and fro?

Answer 127

10-100ml/kg/minute

Question 128

What type of system is an ayres t piece circuit? Does this require high or low fresh gas flow rates? What is the patient weight limit and why? Is it suitable for IPPV?

Answer 128

Non-rebreathing system. Because reservoir bag is on expiratory limb, high fresh gas flow rates required. Used on patients <10kg due to minimal dead space and resistance. Ideal for cats, small dogs and many small mammals. Can be used for prolonged intermittent positive pressure ventilation (IPPV).

Question 129

What type of system is a modified bain? Does this require high or low fresh gas flow rates? What is the patient weight limit and why? Is it suitable for IPPV?

Answer 129

Non-rebreathing system. Because reservoir bag is on expiratory limb, high fresh gas flow rates required. Little dead space but not suitable for patients <10kg. Can be used for prolonged IPPV

Question 130

What type of system is a Magill? Does this require high or low fresh gas flow rates? What is the disadvantage of using this circuit? What is the patient weight limit and why? Is it suitable for IPPV?

Answer 130

Non-rebreathing system. Cannot be used for patients <10kg due to expiration valve pressure. Site of valve is close to patient making head and neck surgery difficult. Because reservoir bag is on inspiratory limb, it is unsuitable for prolonged IPPV

Question 131

What type of system is a mini lack? Does this require high or low fresh gas flow rates? What is the patient weight limit and why? Is it suitable for IPPV?

Answer 131

Non-rebreathing system. Less resistance than Magill with valve is situated away from patient. Because reservoir bag is on inspiratory limb, it is unsuitable for prolonged IPPV. Suitable for patients < 10 kg

Question 132

What type of system is a lack? Does this require high or low fresh gas flow rates? What is the patient weight limit and why? Is it suitable for IPPV?

Answer 132

Non-rebreathing system. Less resistance than Magill with valve situated away from patient. Because reservoir bag is on inspiratory limb, it is unsuitable for prolonged IPPV. Suitable for patients 10 – 20 kg

Question 133

What type of system is a Humphrey ADE? Does this require high or low fresh gas flow rates? What is the patient weight limit and why? Is it suitable for IPPV?

Answer 133

Non-rebreathing system but can be altered to rebreathing by addition of a soda lime canister. Functions as a Lack system for spontaneous respiration and as a T piece with IPPV

Question 134

What type of system is a Circle? Does this require high or low fresh gas flow rates? What is the patient weight limit and why? Is it suitable for IPPV?

Answer 134

Rebreathing system. Efficient use of gas but unsuitable for patients <15 kg due to high resistance. Can be used for IPPV

Question 135

What type of system is a To and fro? Does this require high or low fresh gas flow rates? What is the patient weight limit and why? Is it suitable for IPPV?

Answer 135

Rebreathing system. Efficient use of gas but unsuitable for patients <20 kg due to high resistance. Can be used for IPPV

Question 136

Which circuits are usually appropriate for cats and dogs under 10kg that don't require IPPV?

Answer 136

Mini-Lack T-piece Humphrey ADE (A mode)

Question 137

Which circuits are usually appropriate for cats and dogs under 10kg that require IPPV?

Answer 137

Circle or To-and-Fro (in an emergency) T-Piece or Bain Humphrey ADE (E mode)

Question 138

Which circuits are usually appropriate for dogs 10- 20 kg that don't require IPPV?

Answer 138

Circle or To-and-Fro Lack or Magill Bain Humphrey (Circle mode)

Question 139

Which circuits are usually appropriate for dogs 10-20kg that require IPPV?

Answer 139

Circle or To and Fro Bain Humphrey (Circle mode)

Question 140

Which circuits are usually appropriate for dogs >20 kg that don't require IPPV?

Answer 140

Circle or To-and-Fro | Humphrey (Circle mode)

Question 141

Which circuits are usually appropriate for dogs >20kg that require IPPV?

Answer 141

Circle or To-and-Fro | Humphrey (Circle mode)y

Question 142

What are the benefits of intubation?

Answer 142

Intubation allows for complete control over breathing – enabling alteration in anaesthetic depth, oxygenation and intermittent positive pressure ventilation (IPPV) where necessary. When a cuffed endotracheal (ET) tube is used it prevents aspiration of regurgitated stomach contents back into the airway

Question 143

What are the complications associated with intubation?

Answer 143

there can be complications associated with intubation e.g. damage to the tracheal mucosa, challenging to place (especially in brachycephalics), incorrect placement, blockage etc.

Question 144

What device can help to intubate cats and rabbits?

Answer 144

In cats (or rabbits) a supraglottic airway device (SGAD) may be used instead to avoid some of the complications associated with endotracheal intubation. Using a SGAD will also prevent aspiration if placed correctly (SCVS, 2018). It can also be used for an emergency anaesthetic and delivery of IPPV

Question 145

What are the disadvantages of using red rubber ET tubes?

Answer 145

Red rubber tubes are less often used now as they have several disadvantages- they are prone to kinking, harden with repeated use and are not transparent. P

Question 146

How do you measure an ET tube?

Answer 146

The length of the ET tube should be correct- the tip should lie at the point of the shoulder (suprascapular tuberosity); and the connector be level with the incisors to minimise the risk of dead space in the circuit.

Question 147

How can the correct ET tube position be confirmed?

Answer 147

The correct tube position in the trachea can be confirmed by- ➢ visualising the tube between the vocal folds in the glottis ➢ palpation of the cervical region - if the ET tube is in the oesophagus, two rigid structures may be palpated ➢ noting increased CO2 levels on capnography ➢ noting condensation in the ET tube associated with each breath ➢ auscultation of breathing on both sides of the thorax ➢ movement of both sides of the thorax wall when the reservoir bag is squeezed N.B. this last suggestion may be unreliable as the thorax will move if the reservoir bag is squeezed and accidental oesophageal intubation has been performed

Question 148

What should be used in cats prior to intubation to avoid laryngeal spasm?

Answer 148

Lidocaine (e.g. Intubeaze®) should be sprayed onto the laryngeal folds, prior to intubation in cats, as laryngeal spasm is common.

Question 149

What is the aim of a cuff on an ET tube?

Answer 149

The aim of the cuff, if present, is to prevent aspiration into the lungs and to prevent gas passing around the ET tube, especially important during IPPV. An inflated cuff also minimises environmental contamination with volatile anaesthetics

Question 150

How do you reduce the risk of tracheal damage when using a cuff on an ET tube?

Answer 150

To decrease the possibility of tracheal damage, an ET tube with a high-volume low resistance cuff should ideally be used. The old-style red rubber ET tubes have a low-volume high resistance cuff which is more likely to cause damage to the trachea, although this cuff is more effective at preventing aspiration. The cuff should be suitably inflated to avoid breathing round the tube. Over inflation of any cuff, however, should be avoided as it can cause tracheal damage N.B. it is possible to cause tracheal damage with the high- volume, low resistance cuffs as well. It is sensible to deflate and re-inflate the cuff approximately twenty minutes after induction and repeat this during lengthy anaesthetics. As the muscles around the tube relax, there may be an increased risk of leakage around the tube.

Question 151

What correct cuff pressure should be used when a patient is intubated?

Answer 151

The correct cuff pressure should be ~ 20 – 30 cmH2O at the end of expiration. If a cuff inflating device with a pressure regulator is used, the pressure can be measured. N.B. the cuff pressure does change through the procedure so should be checked intermittently.

Question 152

When should an ET tube be removed and what should be checked prior to removal?

Answer 152

The ET tube should remain in place till the patient can swallow. With cats, the ET tube will be removed slightly earlier to prevent laryngospasm and in brachycephalics it is left longer until they are conscious enough to maintain an open airway. To avoid damage, the cuff should be completely deflated immediately prior to extubation. However, the oral cavity/pharynx should be checked to ensure there is no fluid, debris or regurgitated material present first. In between use, ET tubes should be very well maintained.

Question 153

What is a TIVA and what should it allow to happen?

Answer 153

Total intravenous anaesthesia (TIVA) is the induction and maintenance of anaesthesia via purely intravenous means. Drugs used for TIVA should allow anaesthetic depth to be rapidly changed by altering the infusion rate and should not produce significant accumulation

Question 154

What advantages should the drugs used for TIVA have?

Answer 154

The most suitable drugs will have rapid onset of action, short duration of clinical effects, high clearance rates, rapid metabolism to inactive products, and rapid excretion

Question 155

What are the reasons for using TIVA in veterinary patients?

Answer 155

There are several reasons for TIVA being used in veterinary patients- ➢ decreased environmental contamination ➢ decreased oxygen use ➢ decreased side-effects associated with inhalation/ volatile agents. The absence of a cumulative and hangover effect means these drugs are suitable for TIVA (propofol and alfaxan)

Question 156

What drugs are suitabel for TIVA in dogs?

Answer 156

Both propofol and alfaxalone can be used for TIVA in dogs;

Question 157

What drugs are suitable for TIVA in cats?

Answer 157

alfaxalone is suitable for cats.

Question 158

What are the drugs used for TIVA usually administered with and why?

Answer 158

As neither drug has analgesic properties, they are | usually administered with opioid analgesics +/- dissociative agents e.g. fentanyl and ketamine.

Question 159

Why is propofol not suitable to use in cats for TIVA?

Answer 159

Propofol is not suitable for TIVA in the cat due its poor ability to metabolise by hepatic glucuronidation. Delayed recovery and Heinz body anaemia could be complications of propofol TIVA in cats.

Question 160

What is the potential risk when administering TIVA? What monitoring equipment is needed?

Answer 160

Respiratory depression is a potential risk with both propofol and alfaxalone TIVA and monitoring of ETCO2 should be performed. Patient position should be considered -ventilation will be most effective in patients who can be supported in sternal recumbency.

Question 161

What is PIVA and what are the benefits of it?

Answer 161

Partial intravenous anaesthesia (PIVA) is a combination of total intravenous anaesthetic agent plus a low dose of a volatile/inhalational anaesthetic. This could be an alternative option for critical patients at risk from higher levels of inhalational anaesthesia- reducing side-effects and enhancing analgesia.

Question 162

What drugs can be used for PIVA?

Answer 162

Partial intravenous anaesthesia (PIVA) | Propofol, alfaxalone, opioids, alpha-2 adrenergic agonists and lidocaine can be used in balanced PIVA.

Question 163

What is intermittent positive pressure ventilation?

Answer 163

Intermittent positive pressure ventilation (IPPV) is intermittent, inflation of the lungs by applying positive pressure to the airways to ventilate a patient - sometimes called ‘squeezing’ or ‘bagging’. IPPV requires the patient to be intubated. Whilst of benefit to many patients, IPPV is a complicated technique and must be performed with care to avoid serious complications

Question 164

What are the reasons for performing IPPV?

Answer 164

Reasons for performing IPPV I. entry into the thoracic cavity (e.g. thoracotomy, chest drain placement or diaphragmatic rupture repair). II. apnoea III. hypoventilation resulting in hypoxaemia and hypercapnia IV. cardiopulmonary resuscitation for a patient in cardio-pulmonary arrest V. ventilatory support during prolonged anaesthesia procedures VI. to decrease patient work of breathing e.g. elderly, diseased VII. delicate surgical procedures

Question 165

What are the benefits of doing manual IPPV over mechanical?

Answer 165

Manual IPPV has the advantage of being adaptable and readily employed. It might be required at anaesthetic induction if too rapid administration of propofol or alfaxalone has caused apnoea.

Question 166

What are the disadvantages of doing manual IPPV?

Answer 166

However, as this is dependent on the skill of the person performing the technique, there can be serious complications related to under-ventilation or over-inflation of the lungs. It is also time-consuming- interfering with the ability to monitor the patient’s anaesthetic where staff numbers are limited.

Question 167

How does the compliance of the lungs affect IPPV?

Answer 167

Compliance of the lungs The volume of gas that enters the lungs when a given pressure is applied to the airway is determined by the thoracic compliance. This is, in turn, determined by the compliance of the lungs and the chest wall. Static compliance is basically the elasticity of the lungs and chest wall. A greater compliance means the lungs will inflate more easily and will have a greater volume of air within them for any given airway pressure

Question 168

How does the resistance of the airways affect IPPV?

Answer 168

The resistance of the airways also alters the amount of gas that enters the lungs with a given airway pressure. Obstruction of the airways e.g. a mucous plug, will require a greater airway pressure to achieve a set tidal volume, than if there was no obstruction – i.e. there is higher airway resistance.

Question 169

What is a mechanical ventilators?

Answer 169

Mechanical ventilators Mechanical ventilators are machines which ventilate the patient. There are two main types of ventilator. Volume-limited (a set volume of gas is given per breath) and pressure-limited (a breath is given until a certain airway pressure is reached). With volume-limited, the ventilator may be a ‘bag-in-a-bottle’ where the volume of the bag is the volume of the breath, or it may be pneumatic with the volume determined by gas flow and inspiratory time.

Question 170

What do you need to consider in regards to the anaesthetic when performing IPPV?

Answer 170

IPPV will potentially increase the rate of absorption of inhalational anaesthetic agents, therefore necessitating a reduction in the amount of volatile anaesthetic delivered. IPPV will be required if neuromuscular blocking drugs have been used or if respiratory depression occurs during anaesthesia e.g. administration of full agonist opioid (e.g. fentanyl).

Question 171

What cardiovascular effect can IPPV have?

Answer 171

IPPV will generally improve oxygenation of blood and so improve oxygenation of tissues. However, IPPV may cause a depression in cardiac output. This is because IPPV increases thoracic pressure. This, in turn, can reduce the venous return to the heart resulting in reduced cardiac output. This will be worse in hypovolaemic patients that already have a low central venous pressure.

Question 172

How can you mitigate the effect IPPV has on cardiac output?

Answer 172

To mitigate this effect, the peak inspiratory pressure should be optimal and there should be sufficient time between inspirations. The respiratory rate and tidal volume for IPPV should be the lowest possible to adequately oxygenate the patient, thus, avoiding hypoventilation, hypoxaemia, hypercapnia and respiratory acidosis. Adequate monitoring, ideally with arterial blood gas analysis, but more likely end-tidal capnography and pulse oximetry is essential.

Question 173

What negative effects can over ventilation via IPPV have?

Answer 173

If the patient is over-ventilated, the carbon dioxide levels will fall, leading to respiratory alkalosis. This can lead to a decreased blood pressure (secondary to vasodilation) and so decreased perfusion of vital organs, especially the brain. In a severe case, this could lead to cerebral hypoxaemia and cause brain damage. Overventilation also removes the stimulus to breathe spontaneously by decreasing the amount of carbon dioxide in the bloodstream (PaCO2).

Question 174

Elevated what... is responsible for stimulating the breathing centre in the pons and medulla? Why would overventilation cause a problem?

Answer 174

Elevated PaCO2 is responsible for stimulating the breathing centre in the pons and medulla, so if this is low, there is no stimulation of the respiratory centre. This situation would make it difficult to stop providing IPPV/remove the patient from the ventilator at the end of surgery

Question 175

What tidal volume of IPPV be delivered?

Answer 175

A tidal volume of 10 ml/kg (lower end of normal range) should be delivered-however this cannot be routinely measured when performing IPPV manually.

Question 176

How do you assess whether IPPV is effective?

Answer 176

To assess whether IPPV is effective, movement of the thorax should be observed -effective IPPV should cause a normal chest wall movement. Arterial blood gas analysis is the most accurate way of assessing the effectiveness of IPPV but capnography gives an accurate indication of the Pa CO2

Question 177

Why is it important not to over or under inflate when performing IPPV?

Answer 177

It is important to avoid both over inflation and under inflation when performing IPPV. As well as increasing the depth of anaesthetic, and causing decreased cardiac output, over inflation could cause damage to alveoli and resulting in pulmonary oedema secondary to an acute inflammatory response. Extreme over inflation could cause rupture of alveoli and lead to pneumothorax.

Question 178

What does the respiratory rate for IPPV depend on?

Answer 178

The respiratory rate for IPPV will depend on the circumstances and species e.g. CPR (10/ minute) vs planned thoracotomy (~ 20/minute)

Question 179

What should the ratio of inspiration to expiration time be?

Answer 179

The ratio of inspiration time to expiration time (I:E) should be 1:2 or 1:3

Question 180

What should the inspiratory pressure of IPPV be?

Answer 180

The inspiratory pressure should be ~15 cm H2O

Question 181

Why are the lack and magill anaesthetic circuits not suited for planned IPPV?

Answer 181

The Lack and Magill anaesthetic circuits are not suited for planned manual IPPV because of the risk of the patient rebreathing expired air with a high carbon dioxide level.

Question 182

What should you do prior to removing a patient off of a mechanical ventilator and why? What monitoring equipment should be used on a ventilator and what makes getting a patient off of a ventilator more challenging?

Answer 182

To remove a patient from a mechanical ventilator, it may be necessary to administer 2-3 rapid breaths followed by a pause that breaks the regular rhythm of respiration that can itself be inhibitory. This allows a degree of hypercapnia to develop and provides the stimulus for return of spontaneous breathing. Capnography and pulse oximetry monitoring should be continued to ensure the patient remains adequately oxygenated ion after removal from the ventilator. Careful monitoring is needed for any patient that has received either IPPV or mechanical ventilation. The weaning off process is not always straight forward and becomes more challenging the longer the support has been in place.

Question 183

How can a pulse be measured under anaesthetic?

Answer 183

As well as monitoring central pulses (e.g. femoral), the strength of peripheral pulses should be monitored during anaesthesia, giving an indication of the peripheral circulation. Carpal and metatarsal pulses should be palpated at induction and regularly during the anaesthetic procedure. During anaesthesia, the lingual artery which runs along the ventral surface of the tongue may be used instead of the femoral pulse. Pulse pressure (the strength of the pulse) is the difference between systolic and diastolic pressures and can give a very subjective indication of changes in blood pressure during an anaesthetic. However, blood pressure should ideally be measured directly or indirectly, as appropriate to the patient, as it is much more accurate. Listening to the audible signal from a Doppler blood pressure monitor can help identify early changes in pulse quality and pressures. The pulse rate should be compared to the heart rate to ensure that there is a pulse for every heartbeat. If more heart beats are auscultated than pulses felt, a pulse deficit is present. This is clinically significant and further investigation, including ECG recording, would be needed.

Question 184

How do you monitor the heart under anaesthetic?

Answer 184

The heart may be auscultated directly over the lateral chest wall using a standard stethoscope; however, this must be continuously applied or held in place. Alternatively, an oesophageal stethoscope may be used. The heart rate itself can be a useful indicator of anaesthetic depth- tachycardia may be associated with too light a plane of anaesthesia, pain or falling blood pressure linked to e.g. blood loss. Bradycardia is common in the deeper stages of anaesthesia but can also be caused by certain drugs e.g. alpha- 2 agonists, some opioids. If a patient is so deeply anaesthetised that it is close to cardiac arrest, the sympathetic nervous system may be stimulated leading to an increased heart rate. Therefore, any sudden change in heart rate should be taken seriously; additionally, an irregular heart rhythm (arrhythmia/ dysrhythmia) is potentially very significant and should be identified and reported promptly.

Question 185

How do you monitor the respiration under anaesthetic?

Answer 185

The rate of respiration can be measured by visually observing chest movements and the anaesthetic bag movement N.B. While both should be observed, it is always especially important to watch the patient itself. The breathing pattern should be similar to when the patient is awake, with no excessive thoracic wall excursion. However, because of the potential for hypo and hyperventilation, end tidal CO2 monitoring should be performed. Tachypnoea may be a response to a painful stimulus in an inadequately analgesed patient at a lower plane of anaesthesia. Some anaesthetic drugs can be associated with erratic breathing

Question 186

What is a pulse oximeter used to measure?

Answer 186

a pulse oximeter is used to measure the | percentage of haemoglobin saturated with oxygen (SPO2).

Question 187

Where should a pulse oximeter be placed?

Answer 187

A pulse oximeter is a noninvasive monitoring device requiring the probe to be applied to a non-pigmented area of e.g. the tongue, lip or a skin fold to measure the SPO2.

Question 188

What should the SPo2 be and what does this measurement reflect?

Answer 188

The aim should be to keep the SPO2 level at over 95%. Levels below 92-94% indicate significant hypoxaemia. Pulse oximetry does NOT reflect tissue perfusion or ventilation- only oxygenation of the red blood cells.

Question 189

What are the limitations of a pulse oximeter?

Answer 189

Whilst helpful, pulse oximeters have several limitations which can affect their reliability. Their accuracy will be affected by poor blood flow to an area. In cases of poor perfusion, peripheral vasoconstriction prevents adequate blood flow to the capillary bed (that the pulse oximeter is reading) – leading to an inaccurate result.

Question 190

What is capnography?

Answer 190

Capnography is a non-invasive means of assessing the effectiveness of ventilation by measuring the amount of CO2 that a patient expires (end-tidal CO2/ ETCO2) using a capnograph

Question 191

How can the ETCO2 equate to arterial CO2?

Answer 191

With healthy lungs, end-tidal carbon dioxide levels roughly equate to arterial carbon dioxide concentration (PaCO2) and therefore the reading can indicate the adequacy of ventilation

Question 192

What does high end carbon dioxide levels indicate in anaesthesia?

Answer 192

High end-tidal carbon dioxide levels indicate hypoventilation and low levels indicate hyperventilation or decreased perfusion. If a patient is too deeply anaesthetised, then they will hypoventilate leading to increased ETCO2 readings.

Question 193

How can you test if a pulse oximeter is accurate?

Answer 193

Often pulse oximeters have a waveform display that shows the pulsatile blood flow through the capillary bed. If the waveform is good, and the heart rate that is measured by the ‘pulse-ox’ matches the patient’s actual heart rate, then the value can be trusted. However, if the ‘pulse ox’ heart rate is inaccurate and there is a poor waveform, then the pulse oximeter reading is not reliable.

Question 194

How can you reduce increased CO2 levels in anaesthesia without IPPV?

Answer 194

Reducing the concentration of volatile gas agent being delivered to the patient, should lead to improved ventilation and a reduction to normal levels of expired CO2.

Question 195

How is Co2 in anesthesia proportional to cardiac output?

Answer 195

The end-tidal carbon dioxide level is proportional to cardiac output. Therefore, a sudden fall in cardiac output (e.g. cardiac arrest) will be followed by a rapid decrease in end tidal CO2 because blood is not being delivered to the lungs.

Question 196

What is the normal ETCO2 level during anaesthesia?

Answer 196

The normal ETCO2 is ~ 35 - 40 mmHg which equates to a concentration of about 4% of CO2 in expired air.

Question 197

What should mean arterial blood pressure ideally stay above during anaesthesia?

Answer 197

During anaesthesia, the mean arterial blood pressure | should ideally remain above 70-80mmHg

Question 198

What would be suggestive of hypovolaemia during anaesthesia?

Answer 198

Decreased blood pressure readings indicate that the patient is hypotensive. Decreased blood pressure combined with increased heart rate is suggestive of hypovolaemia and a ‘fluid challenge’ may be indicated in this situation.

Question 199

Central venous pressure represents the pressure from what side of the heart?

Answer 199

Central venous pressure (CVP) represents the pressure in the right side of the heart.

Question 200

How can central venous pressure be measured?

Answer 200

This can be measured by inserting a central venous catheter into a jugular vein to the level of the cranial vena cava. This is then connected to a water manometer. The manometer can be marked off in centimetres with the 0 situated at the same level as the right atrium.

Question 201

What are the normal values for central venous pressure?

Answer 201

Normal values are ~ 0-5 cmH20 or 0-4mmHg.

Question 202

What is central venous pressure affected by and what can this indicate and be used to assess?

Answer 202

CVP is affected by the volume of venous blood returning to the right side of the heart- so can indicate the fluid status of a patient and be used to assess the requirements for and effectiveness of fluid therapy

Question 203

What could an increased and decreased central venous pressure indicate?

Answer 203

Hypovolaemic patients will have decreased CVP; and fluid overload will lead to increased CVP readings. CVP is also affected by other factors such as right-sided heart disease

Question 204

What effect does temperature have on an anaesthetic?

Answer 204

Monitoring of body temperature is essential during anaesthesia to ensure neither hyperthermia nor hypothermia occurs. Hypothermia is more likely during anaesthesia, for various reasons, and can lead to a delayed recovery from the anaesthetic, slowing of the heart rate, reduction in tissue oxygenation and cardiac arrhythmias.

Question 205

What are the various causes of hyperthermia during anaesthesia?

Answer 205

There are various causes of hyperthermia- ➢ iatrogenic e.g. forced warming system, heat pads too many blankets, too warm IV fluids ➢ brachycephalia, obesity, thick coat ➢ breathing system- more likely with rebreathing system ➢ rarely hyperthermia can be due to inherited malignant hyperthermia

Question 206

What are the clinical signs of hyperthermia?

Answer 206

Clinical signs include tachypnoea, hypercapnia, red mucous membranes, muscle tremors, increased temperature and arrhythmias.

Question 207

What serious complications can sevre hyperthermia cause?

Answer 207

Severe hyperthermia (> 40˚ C) must be recognised promptly and managed effectively to avoid brain damage, acute kidney injury and death.

Question 208

What should be recorded on an anaesthetic chart?

Answer 208

The anaesthetic record should be completed in real-time as events happen. All details regarding drugs administered, size and type of endotracheal tube and any notable events should be recorded. In addition, heart rate, respiratory rate, SpO2, ETCO2, blood pressure, temperature and vaporiser and oxygen settings should be recorded every five minutes, or more frequently if the patient’s condition dictates it.

Question 209

What are the benefits of monitoring and recording anaesthesia?

Answer 209

This serves to ensure that the patient is adequately monitored; permits review of the anaesthetic in accordance with clinical governance; and finally, is a legal record of the anaesthetic. It is also important to remember that the patient is closely monitored in between each 5-minute recording on the anaesthetic record. A lot can happen in 5 minutes- if the patient decompensates 30 seconds after the respiratory rate was last counted, it could in theory be apnoeic for 4 and a half minutes before it is recognised. As such continual monitoring of the patient is essential.

Question 210

What post-operative monitoring should patients receive after anaesthesia?

Answer 210

Immediate post-operative monitoring is essential in the critical care patient. Continued monitoring of heart rate and rhythm, respiration rate and body temperature etc. are essential to detect early deterioration. ECG monitoring of the heart rate and rhythm may is beneficial to allow for early detection of problems. Blood pressure monitoring should continue in the post-operative period ensuring the mean arterial pressure remains above 70 mmHg. Pulse oximetry may be used to ensure oxygen saturation stays above 95%- this is especially useful during the recovery period and when the patient has been removed from 100% oxygen delivery. Monitoring of urine output is a valuable indicator of renal perfusion and function (normal ~ 1-2 ml/kg/hr). Monitoring of the time to return to full mentation and standing, if appropriate, should also be recorded.

Question 211

What does the international association for the study of pain define pain as?

Answer 211

‘The International Association for the Study of Pain has defined pain as “an unpleasant sensory and emotional experience associated with actual or potential tissue damage or described in terms of such damage”. Pain is, therefore, a subjective emotion’

Question 212

What is the purpose of the body feeling pain?

Answer 212

Pain is a protective mechanism, a response to actual or potential tissue damage. There are different types and causes of pain - it is a complex process and affected by many factors.

Question 213

What is the purpose of nociceptive pain?

Answer 213

The biologic function of acute (nociceptive) pain is to warn and protect the patient.

Question 214

What is inflammatory pain associated with and what's the time scale it occurs within?

Answer 214

Inflammatory pain is associated with actual tissue damage and the release of inflammatory chemicals. Depending on the underlying cause, degree of injury and area of the patient affected, this pain can be severe. It should, however, resolve within a short timescale of the cause being removed and should be self-limiting

Question 215

What does neuropathic/pathological pain arise from?

Answer 215

Neuropathic/ pathological pain is pain arising from a nerve injury but may also be due to dysfunction in the nervous system.

Question 216

How is neuropathic pain usually displayed?

Answer 216

With neuropathic pain, a patient feels pain in the absence of current tissue damage or the original cause of pain has been removed. An example of this is when a patient reacts as though in pain to a nonpainful stimulus e.g. marked pain response to a subcutaneous injection in a Greyhound or a patient with ongoing pain after amputation of an irreparably fractured limb

Question 217

What problems can neuropathic pain present in the veterinary patient?

Answer 217

Neuropathic pain can be greater than it should be relative to the amount of tissue damage (hyperalgesia) or can be caused by non-painful stimuli (allodynia) and can be a significant issue for veterinary patients. Both can be the cause of e.g. behavioural problems in veterinary patients.

Question 218

What type of pain is neoplastic pain and what is it caused by?

Answer 218

Neoplastic pain is a type of pathological pain and can be caused by tumour cell invasion/ destruction but also by chemicals released by the tumour. ECC patients may also present with clinical signs relating to pathological pain.

Question 219

What are the four components to pain physiology?

Answer 219

There are four components to pain physiology (Nursing Times, 2008) – ❖ transduction (pain receptors ‘nociceptors’ are stimulated by noxious stimuli) ❖ transmission (pain impulses are transmitted to the spinal cord and then towards the brain) ❖ modulation (modifying of the pain messages being transmitted to the brain. They can be increased/amplified or decreased/ weakened) N.B. the more pain messages the brain receives, the more pain the patient will feel. ❖ perception (conscious perception = the animal is aware it in pain/ it feels pain)

Question 220

Describe the transduction component of pain physiology?

Answer 220

pain receptors ‘nociceptors’ are stimulated by noxious stimuli

Question 221

Describe the transmission component of pain physiology?

Answer 221

(pain impulses are transmitted to the spinal cord and then towards the brain)

Question 222

Describe the modulation component of pain physiology?

Answer 222

modifying of the pain messages being transmitted to the brain. They can be increased/amplified or decreased/ weakened) N.B. the more pain messages the brain receives, the more pain the patient will feel.

Question 223

Describe the perception component of pain physiology?

Answer 223

(conscious perception = the animal is aware it in pain/ it feels pain)

Question 224

What is nociception?

Answer 224

Nociception is the sensory part of the pain pathway. Processing of pain messages by the CNS following stimulation of pain receptors ‘nociceptors’ = physiological pain. There are various types of nociceptors with different stimuli and levels of sensitivity (i.e. what they respond to) –thermal, high and low threshold mechanical, chemical and polymodal.

Question 225

What are the 4 different types of nociceptors?

Answer 225

➢ Mechanoreceptors respond to touch, pressure, vibration and stretch ➢ Thermoreceptors are sensitive to changes in temperature ➢ Chemoreceptors are sensitive to chemical changes ➢ Polymodal are sensitive to several stimuli – mechanical, chemical and thermal

Question 226

What do mechanoreceptors respond to?

Answer 226

respond to touch, pressure, vibration and stretch

Question 227

What do thermoreceptors respond to?

Answer 227

Thermoreceptors are sensitive to changes in temperature

Question 228

What are chemoreceptors sensitive to?

Answer 228

Chemoreceptors are sensitive to chemical changes

Question 229

What are polymodal sensitive to?

Answer 229

Polymodal are sensitive to several stimuli – mechanical, chemical and thermal

Question 230

Nociceptors are stimulated when they exposed to what?

Answer 230

Nociceptors are stimulated when exposed to noxious stimuli (due to tissue trauma, inflammation, ischaemia, infection, surgery etc.).

Question 231

What different classes can nociceptors be put in to in regards to their location?

Answer 231

``` By location, nociceptors are classed as superficial somatic (skin, and mucous membranes); deep somatic (muscles, tendons, joint capsules, bone etc.) and visceral (peritoneum, pleura, internal organs etc.). Silent receptors do not tend to respond to heat or chemical stimulation – however will react to inflammation in some situations (e.g. mechanical stretching) ```

Question 232

Where would a superficial somatic nociceptor be located?

Answer 232

superficial somatic (skin, and mucous membranes)

Question 233

Where would a deep somatic nociceptor be located?

Answer 233

(muscles, tendons, joint capsules, bone etc.)

Question 234

Where would a visceral nociceptor be located?

Answer 234

visceral (peritoneum, pleura, internal organs etc.).

Question 235

What type of nociceptors does visceral tissue have and how does this effect it?

Answer 235

Visceral nociceptors are often silent but can be stimulated by distension of an organ/capsule, inflammation or by ischaemia. Visceral pain can be hard to localise and is often referred i.e. pain is felt elsewhere.

Question 236

Describe the pain pathway from stimulation of the nociceptor?

Answer 236

Once nociceptors are stimulated, nerve impulses are generated and transmitted via afferent/ sensory neurons to the dorsal horn of the spinal cord and then in sensory tracts towards the brain

Question 237

What are the two types of pain transmitting sensory neurons?

Answer 237

There are two types of pain transmitting sensory neurons - fast (A-delta) and slow (C) neurons.

Question 238

What do the fast neurons (A-delta) transmit?

Answer 238

The fast neurons transmit the initial pain | messages which, when analysed, produce pain which is sharp, stinging and localised – first pain;

Question 239

What do the slow neurons (C) transmit?

Answer 239

the C neurons transmit more slowly and for longer, resulting in more widespread dull/ aching/burning, slow pain. N.B. The more inflammatory chemicals/ mediators that are released because of tissue injury, the greater the number of pain messages that are transmitted

Question 240

What type of neurons are responsible for peripheral sensitisation?

Answer 240

This is peripheral sensitisation and is an important consideration when managing patients. the C neurons transmit more slowly and for longer, resulting in more widespread dull/ aching/burning, slow pain. N.B. The more inflammatory chemicals/ mediators that are released because of tissue injury, the greater the number of pain messages that are transmitted

Question 241

What is pain modulation?

Answer 241

The number of pain impulses transmitted to the brain may be amplified or decreased because of several complex nerve pathways that interact with the dorsal horn. The more pain messages that are transmitted, the more pain the patient will feel. Modulation is one of the reasons that two patients will appear to experience quite different levels of pain following the same injury.

Question 242

What is released in an animals body to inhibit the transmission of pain messages?

Answer 242

``` Endogenous opioids (i.e. those released by the animal) inhibit the transmission of pain messages, as do the neurotransmitters gamma-aminobutyric acid (GABA) and serotonin ```

Question 243

What is involved in an animal's pain perception?

Answer 243

The pain impulses are transmitted from the spinal cord to the brain stem (pons, medulla, midbrain) and thalamus. From the thalamus, they are directed to various other zones in the brain where they are processed- hypothalamus, limbus and ultimately the cerebrum. It is because pain messages are processed in different areas of the brain that an animal can demonstrate a variety of clinical signs following an injury- and there is no one clinical finding that indicates pain

Question 244

When is pain consciously perceived?

Answer 244

Pain is consciously perceived (i.e. the patient is aware of being in pain) when the nerve impulse reaches the cerebrum/forebrain.

Question 245

What signs is conscious awareness of pain associated with?

Answer 245

Conscious awareness of pain is associated with various species-dependent responses e.g. whining, turning to look, trying to bite, freezing etc.

Question 246

What are signs of pain reaching the pons and the medulla?

Answer 246

Pain impulses reaching the pons and medulla can lead to increased heart rate and respiratory rate

Question 247

What do pain impulses reaching the hypothalamus lead to?

Answer 247

Pain impulses reaching the hypothalamus lead to the release of catecholamines (adrenaline and nor-adrenaline) and the stress hormones (cortisol/cortisone) – ‘neuro-endocrine connection’. This can lead to clinical findings of increased heart rate, tachypnoea, hypertension, hyperglycaemia etc. and can potentially lead to catecholamine induced arrythmias, in some patients.

Question 248

What can pain impulses reaching the limbus/amygdala lead to?

Answer 248

Pain impulses reaching the limbus/ amygdala can cause behavioural responses such as fear and anxiety etc.; and are important in forming memories associated with an emotional event which can result in learned fear

Question 249

What is pain sensitisation?

Answer 249

Sensitisation For various reasons, the physiological pain response can be inappropriate resulting in sensitisation and chronic neuropathic/ pathological pain. This can arise for many reasons and is an important consideration when nursing emergency cases, most of whom will be suffering varying degrees of pain due to trauma or illness.

Question 250

What is Allodynia?

Answer 250

Allodynia is when a patient feels pain from a non-noxious stimulus e.g. stroking lumbar region in a cat. This can be linked to previous experiences. Pain perception may be exponentially increased by central nervous system and peripheral nervous tissue sensitisation to all stimuli. N.B. In this situation the patient will feel pain even if a non-painful stimulus has been applied.

Question 251

What is hyperalgesia?

Answer 251

Normally mildly painful stimuli induce a marked pain response i.e. the patient feels more pain than it really should. This is CNS sensitisation/ wind-up and can be associated with anxiety or fear from previous painful experiences.

Question 252

What clinically significant problems can pain sensitisation or wind up lead to?

Answer 252

Sensitisation/wind-up can lead to clinically significant problems including - 1. More severe pain perception 2. Less effective response of analgesics 3. Ineffective monomodal analgesia 4. Behaviour issues- e.g. fear, anxiety, aggression

Question 253

What processes might allodynia and hyperalgesia arise by?

Answer 253

Allodynia and hyperalgesia arise by several processes. One cause is stimulation (primarily via C-fibres) of the dorsal horn cells of the spinal cord. This affects Nmethyl-D-aspartate (NMDA) receptors causing amplification of the pain response- ‘wind-up’

Question 254

What may be the clinical signs of pain?

Answer 254

``` Demeanour - fearful, quiet, attention seeking, aggression, agitated, depressed Anorexia, Hyporexia, polyphagia Hiding Hypertension Altered mobility, abnormal posture, lameness, wound interference Altered faecal output Mydriasis Ptyalism Self-mutilation Tachycardia Tachypnoea Vocalisation- increased or decreased N.B. Absence of these signs, however, does not mean the animal is not feeling pain. ```

Question 255

What may ongoing stimulation of the sympathetic nervous system in a patient in pain result in?

Answer 255

* Fear and anxiety * Delayed wound healing * Ileus * Altered respiratory pattern * Increased risk of pneumonia * Prolonged anaesthetic recovery * Altered cardiovascular function * Reduced food intake * Increases likelihood of infection * Decreased wound healing

Question 256

What does the PLATTER acronym represent in accordance to effective pain management?

Answer 256

``` Epstein at al. (2015) advise that the PLATTER acronym should be applied to ensure continuous, effective pain management for veterinary patients. PLATTER- ❖ Plan ❖ Anticipate ❖ TreaT ❖ Evaluate and Return ```

Question 257

What is validation of a pain scoring system and why is this important?

Answer 257

Validated pain scoring systems that are currently used for dogs, cats and rabbits. Validation of a pain scoring system means that it has been evaluated and proven to be reliable and repeatable in the species it is intended for. Using a validated pain score, enables more objectivity in pain assessment; it can be used by multiple users for the same patient and should effectively detect when a patient requires analgesia. Pain scoring systems that are not validated are not likely to identify a patient in need of analgesia, making them of no clinical use

Question 258

What are the 6 categories used in the Glasgow scale for assessing pain?

Answer 258

The six categories are - posture, comfort, vocalisation, demeanour, mobility, attention to wound and response to touch

Question 259

For a pain scoring system to be an effective clinical tool what should it possess?

Answer 259

For a pain scoring system to be an effective clinical tool it should ❖ be validated ❖ enable the patient to be assessed consistently by multiple users ❖ be easy to complete ❖ permit a numerical score to be assigned

Question 260

Aside from analgesia what other nursing interventions can help to relieve pain, stress or make the patient comfortable?

Answer 260

Nursing interventions should be patient specific but could include • ensuring appropriate environment with hides • minimising environmental noise • ensuing appropriate attention to toileting needs • combining treatments/ monitoring to limit patient disturbance • use of warm or cold compresses if appropriate • tender loving care

Question 261

What 3 types of drug combination/protocols should nurses be aware of?

Answer 261

It is essential to be aware of the drugs that are available for analgesia and the current (up to date) protocols for their use. Synergy, pre-emptive and multi-modal administration are important concepts in pain management- although as discussed previously pre-emptive administration of analgesics is less likely to be an option in ECC patients.

Question 262

What several classes of drugs are analgesias divided in to?

Answer 262

There are several classes of drugs which can be used to provide analgesia o Opioids o Non-steroidal anti-inflammatory drugs (NSAIDs) o Local anaesthetics o Paracetamol o Others

Question 263

What is the definition of analgesia?

Answer 263

Analgesia is insensibility to pain

Question 264

What is the definition of analgesic?

Answer 264

Analgesic- a drug which reduces the perception of pain. Analgesics interrupt the ascending pain pathway at various locations and levels (peripheral, spinal and supra-spinal).

Question 265

What physiological effects do synthetic opioids have in the body?

Answer 265

Synthetic opioids bind to opioid receptors (mainly mu and, sometimes, kappa) in the brain and spinal cord, possibly in peripheral tissues, to exert an analgesic effect by modulating transmission of pain impulses. There are also delta receptors (modulate the effect at mu receptors) and sigma receptors (responsible for many of opioid sideeffects).

Question 266

What type of receptor binding would provide the most effective and safest opioids effects?

Answer 266

The most effective and safest synthetic opioids would have maximal effect at mu receptors (to provide analgesia) and minimal effect at sigma receptors (side effects)

Question 267

What 4 groups are opioids classified in to?

Answer 267

pure agonist partial agonist agonist-antagonist antagonist

Question 268

What is a pure agonist?

Answer 268

pure agonists – maximum analgesic effect as they effectively modulate (block) transmission of pain impulses e.g. morphine, methadone, fentanyl and pethidine

Question 269

What is a partial agonist?

Answer 269

partial agonists – less effective at modulating (blocking) pain transmission therefore less effective analgesics e.g. buprenorphine.

Question 270

What is an agonist atagonist?

Answer 270

agonist–anntagonist – have an antagonistic effect at mu receptors but an agonist effect at kappa receptors to provide very weak analgesia e.g. butorphanol

Question 271

What are antagonists?

Answer 271

antagonists –bind to opioid receptor sites but do not modulate (block) transmission of pain messages i.e. they have no analgesic activity e.g. naloxone. USED AS A REVERSAL

Question 272

Which type of opioids can be titrated with no ceiling effect? What is the downside to this?

Answer 272

Pure agonists can be titrated to effect and do not have a ceiling effect i.e. the larger amount given the greater the level of analgesia although there is a greater risk of side effects with higher doses

Question 273

What type of opioids have a ceiling effect?

Answer 273

Partial agonists do, however, have a ceiling effect i.e. a maximum level of analgesia that they will provide. They also a greater affinity for the mu receptor sites (more potent) than pure agonists. If a patient has been administered a pure agonist and a partial agonist is administered at the same time/ soon after, the partial agonist will displace/ ‘knock off’ the pure agonists from the mu receptors, resulting in less analgesia (less effective) for the patient. A partial agonist should ideally not be administered if there is any possibility that more profound analgesia will be required e. g. full agonist

Question 274

If an antagonist is not available to use in an opioid overdose what can be used?

Answer 274

The antagonist, naloxone may be administered if a patient has had an opioid overdose. However, if naloxone is not available either an agonist–antagonist (butorphanol) or a partial agonist (buprenorphine) may be administered to displace the pure agonist.

Question 275

What are the routes of administration for opioids?

Answer 275

Depending on the preparation, opioids can be administered by several routes – may be IV, IM, SC, epidural, transdermal and oral. Those that can be administered IV may be administered as an intermittent bolus or constant rate infusion (CRI). They are often used for short-term rescue pain.

Question 276

What are the potential side effects for opioids?

Answer 276

Potential side-effects of opioids include – •respiratory depression •sedative effect (excitement in cats if too high dose administered) •miosis •dysphoria •GI effects- morphine causes vomiting initially; decreased peristalsis can lead to constipation. •they have minimal effect on the cardiovascular system but side-effects could include bradycardia and hypotension •(dependence)

Question 277

Why is a multimodal approach with opioids usually used?

Answer 277

However, the higher the dose the greater the likelihood of side effects. Therefore a multimodal approach is commonly used, with opioids being one part of the approach e.g. opioids combined with local anaesthetic techniques

Question 278

What is the main reported side effect with opioids?

Answer 278

The main reported side-effect of opioid administration is respiratory depression, although is uncommon in conscious patients if used appropriately. The respiratory depression may be worse when combined with other depressive drugs during general anaesthesia, thus the requirement for close monitoring. Dysphoria can be associated with higher doses of opioids, repeated administration or longer lasting preparations. It is important to be able to differentiate a patient who is dysphoric (adequate/ excessive analgesia) and a patient in distress (needs analgesia).

Question 279

What is one of the main benefits of using opioids?

Answer 279

One of the main benefits of opioids is that they cause minimal to no cardiovascular depression which is especially useful in emergency patients

Question 280

How long does Methadone last?

Answer 280

Methadone: as with morphine, methadone provides highly effective analgesia, also with a duration of action of around 4 hours.

Question 281

Why is Methadone often the first choice of analgesia for an ECC patient?

Answer 281

Methadone provides highly effective analgesia, also with a duration of action of around 4 hours. Methadone is licensed for dogs and cats (UK) and does not cause vomiting, nausea or histamine release, so is often the first choice of analgesic for an ECC patient

Question 282

What is the duration of action of Morphine?

Answer 282

Morphine: being a full mu agonist, morphine also provides highly effective analgesia, with a duration of action of around 4 hours

Question 283

Why is Morphine not the first choice of analgesia in emergency patients?

Answer 283

However, as it is not licensed for dogs and cats (UK), it is not likely to be the first choice of opioid. The preservative free version, however, can be used for epidural administration. Because it can cause histamine release, IV administration should be performed slowly. It can cause nausea and vomiting and at higher doses can induce dysphoria and excitation in cats. Because of the risk of vomiting, it should not be used in a patient with increased intraocular or intracranial pressure.

Question 284

Why is pethidine not the first choice of analgesia in emergency patients?

Answer 284

Pethidine: also works at mu receptors sites to produce good analgesia. It has a rapid onset of action but is also very short-acting, meaning repeated doses are required if it is used for analgesia

Question 285

Why should pethidine not be administered IV?

Answer 285

It cannot be given by the IV route as it causes a large | release of histamine which could cause anaphylaxis.

Question 286

Why is fentanyl a good choice of analgesia for emergency patients and why is it usually administered as a CRI?

Answer 286

Fentanyl: is a very potent pure mu agonist providing good analgesia but of very short duration – it can be very useful in ECC patients. Because, IV administration can cause respiratory depression at higher doses, especially in anaesthetised patients, it is often administered as a constant rate infusion.

Question 287

Describe how a fentanyl patch works?

Answer 287

Fentanyl is also formulated as a slow release patch which can provide analgesia for 3-5 days in dogs and cats – not currently licenced in the UK. The patch can be applied to a clipped area of skin. The fentanyl is slowly released and slowly absorbed from the site. Consequently, there is a slow onset of action (18-24 hours) meaning that a patch is not suitable for first-line treatment in an ECC patient. The patch must be applied where a patient cannot get at it due to the risk of accidental ingestion. BSAVA (2019) advise of precautions when using, especially if a patient is sent home with a patch in place

Question 288

What might be the problem with providing a patient with more advanced analgesia after giving buprenorphine?

Answer 288

Buprenorphine: has a long duration of action and a high affinity for mu receptors (potent), binding more readily than pure agonists e.g. morphine or methadone. However, buprenorphine is less effective at modulating/ blocking transmission of pain messages than pure agonists so provides less effective analgesia and there is a plateau effect meaning it is less useful for severe pain. Because of the strong binding of buprenorphine to mu receptors, if it is administered initially to a patient which subsequently requires a ‘stronger’/ more effective opioid e.g. methadone, there may be a problem. If a pure opioid is administered after buprenorphine, it may not, in theory, be able to displace buprenorphine from the mu receptors to provide enhanced analgesia. This demonstrates the importance of fully assessing the patient’s pain level before administration of buprenorphine. If there is any doubt as to the level of pain a patient is in, a pure agonist is likely to be a better choice of analgesic in the first instance

Question 289

What is the most common administration route of buprenorphine in cats?

Answer 289

Buprenorphine provides good analgesia to cats and can be absorbed effectively via the transmucosal route in this species unlike dogs (Warne et al., 2014) (Stein, 2005). ZeroPainPhilosophy (2019) cite studies which indicate the sublingual route is as effective as the IV route in cats.

Question 290

What is the duration of action for buprenorphine?

Answer 290

It has a slow onset (~30 minutes) and lasts for 6-8 hours depending on the route of administration. Patients should be assessed and additional doses administered when required

Question 291

What is butorphanol used for?

Answer 291

Butorphanol: Butorphanol is an ineffective analgesic compared to the pure and partial agonists (Warne et al., 2014), although it has significant sedative and antitussive effects. It is mainly used as a sedative alone or in combination with other drugs e.g. acepromazine or an alpha-2 agonist depending on the patient’s clinical status.

Question 292

What effects do NSAIDS have ?

Answer 292

These drugs have varying degrees of anti-inflammatory, anti-pyretic and analgesic effects but they are less effective analgesics than opioids.

Question 293

What do NSAIDS inhibit?

Answer 293

NSAIDs inhibit the cyclooxygenase (COX) enzyme which produces the prostanoidsprostaglandins, prostacyclins and thromboxanes from arachidonic acid.

Question 294

What is the main role of prostaglandins?

Answer 294

Prostaglandins have several roles including being pro-inflammatory mediators i.e. they have an important role in the inflammatory process. Blocking prostaglandin production results in decreased inflammation so decreased release of inflammatory chemicals to stimulate nociceptors. Prostaglandins, however, have an important role in regulating blood flow to peripheral tissues e.g. gastric mucosa and kidneys

Question 295

What are thromboxanes important for?

Answer 295

Thromboxanes are important for platelet aggregation and haemostasis.

Question 296

What are the two iso- enzymes of cyclo-oxygenase? What is blocking both of these enzymes associated with?

Answer 296

There are two iso-enzymes of cyclo-oxygenase (COX) - COX-1 and COX-2. Blocking both is more likely to be associated with side-effects.

Question 297

What is COX-2 anti inflammatory mostly involved with?

Answer 297

COX-2 is the version that is | mostly involved in inflammation - steroids

Question 298

What is COX-1 anti inflammatory responsible for?

Answer 298

COX-1 is responsible for maintaining blood | flow to kidneys, GIT etc

Question 299

Which type of enzyme in NSAIDS are potentially less likely to cause side effects?

Answer 299

NSAIDs that are COX-1 sparing are potentially less likely to cause side-effects.

Question 300

Why are NSAIDS generally not used for ECC patients?

Answer 300

However, whilst NSAIDs have an important role in the management of acute pain they are often not suitable for ECC patients because of their potentially serious sideeffects in patients with acute kidney injury, gastro-intestinal problems, hypotension, hypovolaemia, blood loss, disorders of haemostasis etc.; and as previously mentioned they are less effective analgesics than opioids. They should be used with caution in patients with hepatic disease.

Question 301

What type of drug is paracetamol and what effects does it have?

Answer 301

Paracetamol is not a true NSAID. It has some analgesic and antipyretic effects but is a less effective anti-inflammatory agent (Robinson, 2016). It is thought to have more of a central effect on pain management than true NSAIDs.

Question 302

Why is paracetomol more likely to be used in ECC patients over NSAIDS?

Answer 302

it is likely to cause the NSAID gastro-intestinal and renal side-effects, associated with inhibition of peripheral COX enzymes- meaning that it can possibly be used in patients with bleeding, gastrointestinal disease or where corticosteroids have been administered

Question 303

What type of anaesthesia does paracetamol provide if given alongside opioids?

Answer 303

In some situations, paracetamol could be administered alongside opioid treatment, as multi-modal analgesia, to provide enhanced analgesia and decrease the amount of opioid required. Paracetamol is less effective than opioids for severe pain.

Question 304

Can cats have paracetamol?

Answer 304

Paracetamol should never be used in cats, however. There is no safe dose and even low doses have caused toxicity (Robinson, 2016). Toxicity can arise in dogs but at much higher doses than in cats.

Question 305

How can ketamine be administered?

Answer 305

Ketamine: this dissociative anaesthetic can be administered as a bolus or a constant rate infusion

Question 306

What is ketamine commonly used in combination with?

Answer 306

Ketamine: this dissociative anaesthetic can be administered as a bolus or a constant rate infusion, at sub-anaesthetic dosages, often in combination with morphine and lidocaine. Can be used with fentanyl

Question 307

What effects does Ketamine have?

Answer 307

At these doses, it produces no anaesthesia or dissociative effects. Ketamine binds to N-methyl-D-aspartate (NMDA) receptors in the dorsal horn and has an important role in preventing CNS ‘wind-up’ / hyperalgesia (where heightened sensitisation of the CNS causes an excessive pain response). It also improves opioid receptor sensitivity and reduces tolerance to opioids, so, making them more effective analgesics (Robinson, 2016). In addition, it appears to reduce rebound hyperalgesia which can occur when opioid medication has stopped. Its main function is therefore as an adjunctive analgesic, potentiating opioids, in particular, and preventing ‘windup’.

Question 308

What effects does medetomidine have on the body and what happens when it is used in conjunction with an opioid?

Answer 308

Medetomidine and dexmedetomidine- Like opioids, alpha-2s exert an analgesic effect through spinal and supraspinal mechanisms (Robinson, 2016). They might also have a similar action to local anaesthetics. Due to alpha-2 receptors being located near or in the same places as opioid receptors and because they work in a similar fashion, alpha-2 adrenergic agonists, such as medetomidine/ dexmedetomidine, can have a synergistic or additive effect when used in conjunction with an opioid.

Question 309

Does medetomidine have analgesic properties? What happens with increased doses?

Answer 309

At low doses, the analgesic response to the alpha-2 drugs is dose dependent. However, there is a cut-off point at which further doses of alpha-2 drugs do not increase analgesia, but merely prolong and deepen sedation. The analgesic effect is shorter-lived than the sedative effect. If they are being administered for their analgesic effect, it is usually at a low (micro) doses, alongside another product and as a CRI

Question 310

What are the side effects with alpha- 2 drugs?

Answer 310

Side-effects with alpha-2 drugs are common although less with micro-doses. Initially, systemic hypertension and bradycardia develops followed by hypotension. Additional side-effects include hypoventilation and oxygen desaturation, vomiting, increased urinary output, transient hyperglycaemia, increased myometrial tone and intrauterine pressure. As such, there are many contra-indications to their use, especially in emergency patients

Question 311

What effect does local anaesthetics have?

Answer 311

Local anaesthetics are the ultimate analgesics as they reversibly block transmission in sensory and motor neurons. They act on peripheral nerves - blocking sodium channels which results in decreased transmission of pain impulses in A and C neurons. The effect they have depends on where they are applied. They can stop all pain messages being transmitted and should be used more routinely in pain management.

Question 312

Can local anaesthetics be used as multi-modal analgesia?

Answer 312

They also have a synergistic effect with other analgesics and so have an important role in multi-modal analgesia.

Question 313

What are the disadvantages of local anaesthetics and what side effects can they have?

Answer 313

However, they must be used with caution as they can be toxic, especially the more potent ones and especially to cats. They also block sodium channels in the myocardium which at toxic doses can cause arrhythmias, gastrointestinal and neurological signs

Question 314

What can local anaesthetic toxicity be treated with?

Answer 314

Local anaesthetic toxicity can | be treated with intravenous lipid emulsion.

Question 315

What are the different ways in which local anaesthetic can be administered?

Answer 315

``` Local anaesthetic drugs are very versatile and can be administered in many ways to provide analgesia – • Specific Nerve blocks • Epidural • Spinal • Regional • Intercostal • Intrapleural • Patches** new but potentially useful • Topical e.g. larynx • Intra-articular • Wound splash • Intravenous regional anaesthesia (IVRA although it is not licenced for IV use) ```

Question 316

Is local anaesthetic injected in to nerves?

Answer 316

Local anaesthetic is not injected into nerves but around them to avoid damage. The use of ultrasound guidance and nerve locators improve the accuracy and effectiveness of some nerve blocks techniques

Question 317

What is the only licensed veterinary preperation for local anaesthetic?

Answer 317

Lidocaine

Question 318

What is lidocaine also used for aside from a local anaesthetic?

Answer 318

Previously known as lignocaine, this local anaesthetic is also used as an anti-arrhythmic agent in the emergency management of ventricular tachycardia

Question 319

What physiological effect does lidocaine have?

Answer 319

it binds to receptors inside voltage gated sodium ion channels on the nociceptor nerve membrane, thus, slowing the rate of depolarisation and preventing the creation of a nerve action potential. Smaller nerve fibres, such as the pain fibres, are more susceptible to this effect than the larger sensory and motor fibres

Question 320

What is the onset of action and duration of action for lidocaine?

Answer 320

It has a relatively | rapid onset and duration of action of 1-2 hours.

Question 321

What long does bupivicaine last?preparations does lidocaine come as and what drug protocol can it be used in?

Answer 321

Lidocaine is available as a gel, ointment, patch, spray and injectable solution- the injectable solution, without adrenaline, is most used. It can be used in combination IVwith other drugs in a CRI and as part of TIVA or PIVA.

Question 322

What can bupivicaine be used for?

Answer 322

Bupivicaine. | Bupivicaine can be used for spinal, epidural, or local blocks.

Question 323

How long does bupivicaine last?

Answer 323

It has a long duration of action (up to 8 hours) and therefore should not be repeated within 4-6 hours, as this can lead to toxic effects

Question 324

Which type of bupivicaine is less cardiotoxic?

Answer 324

Levobupivacaine is less cardiotoxic than bupivicaine.

Question 325

What is ropivicaine?

Answer 325

Ropivicaine. Ropivicaine is a long-acting, local anaesthetic with a similar activity to bupivacaine. It should also not be administered IV

Question 326

What should be checked in preperations of lidocaine?

Answer 326

Bupivicaine and ropivicaine are not licenced for use in cats and dogs. Injectable lidocaine is licenced for nerve blocks and regional anaesthesia in dogs and cats; lidocaine spray is licenced for local anaesthesia of the larynx in cats (Intubeaze®). It is important to check whether the preparation contains adrenaline/epinephrine before administration.

Question 327

What is tramadol and what does it do?

Answer 327

Tramadol has opioid like activity at the mu receptor, and inhibits serotonin and noradrenaline reuptake, but appears to be unpredictable in managing canine pain.

Question 328

Why is tramadol rarely used in veterinary patients? When is it usually prescribed?

Answer 328

Tramadol has opioid like activity at the mu receptor, and inhibits serotonin and noradrenaline reuptake, but appears to be unpredictable in managing canine pain. There is little evidence to support the use of tramadol as an analgesic in veterinary patients and its efficacy is debatable (Budsberg et al., 2018). Anecdotally, it appears to work best when co-administered with NSAIDs for chronic pain management; but some dogs seem to be nonresponsive while others seem to be “over-medicated”. Unlike conventional opioids, it is not an appropriate analgesic for rescue pain. Currently tramadol is used when NSAIDs do not provide sufficient analgesia alone, or when NSAIDs cannot be given. Recent research (Murrell, 2014) suggests that the analgesia provided by tramadol is less than that provided by NSAIDs. It is only available as an oral preparation and is often prescribed for patients when they go home

Question 329

What is the epidural space?

Answer 329

The epidural space surrounds the spinal cord and meninges – it contains blood vessels, connective tissue and fat.

Question 330

What is epidural anaesthesia?

Answer 330

Epidural anaesthesia is administration of local anaesthetic into the epidural space and epidural analgesia is administration of an opioid into the epidural space.

Question 331

What are epidurals mainly used for in veterinary patients?

Answer 331

Epidurals are mainly used for procedures or conditions caudal to the diaphragm - especially the hind limbs, pelvis and perineal region. Epidural analgesia may be used during a caesarean or for the management of acute abdominal pain associated with pancreatitis if the patient is haemodynamically stable. N.B. the use of thoracic epidural analgesia has been reported to help control pain associated with acute pancreatitis

Question 332

What are the main risks associated with epidural anaesthesia?

Answer 332

However, there are more risks associated with high epidurals including paralysis of respiratory muscles. N.B. an alternative method of administering local anaesthetic, intrathoracic (i.e. pleural) blocks is reported to be highly effective in treating pancreatic pain (Whittemore and Campbell, 2019). A coccygeal epidural can be used in a cat with feline lower urinary tract disease

Question 333

What drugs can be used for epidurals?

Answer 333

Lidocaine and morphine (alone or in combination) have traditionally been used, offlicence, for epidurals. However, other more potent local anaesthetics (especially bupivacaine can also be used) and other opioids including fentanyl and methadone. If opioid alone e.g. morphine is used, analgesia will be provided but motor function will be retained.

Question 334

What are the contraindications for epidural anaesthesia?

Answer 334

Contra-indications include sepsis, coagulopathy, thrombocytopaenia, hypovolaemia, infection or fractures at the injection site.

Question 335

What is the technique for performing epidural anaesthesia?

Answer 335

Once the patient is anaesthetised and positioned, in sternal (preferred) or lateral recumbency, the injection site is aseptically prepared – usually this is the lumbosacral joint. Sternal positioning is often easier for the hanging drop technique but a patient with a hindlimb injury e.g. fracture may be better positioned in lateral recumbancy. The wings of the ilium are palpated and an imaginary line drawn between these two points passing over the dorsal spinous process of L7 lumbar vertebra. Caudal to this line, an indentation can be palpated in the midline- the L7/S1 intervertebral space. An appropriately sized spinal needle (~ 20-22G, 1-3 inch) is inserted perpendicular to the skin into the L7/S1 depression. The stylet is kept in place at this stage to prevent blockage/ introduction of skin plug into the epidural space. At this stage, for a patient in sternal recumbancy, the stylet is removed and a drop of sterile saline can be placed on the hub of the needle to form a meniscus, if the hanging drop technique is to be performed. A popping sensation may be apparent as the ligamentum flavum is penetrated and the needle enters the low-pressure epidural space. If the hanging drop technique is being used, correct entry of the epidural space is usually indicated by the saline drop being drawn into the epidural space. Correct location in the epidural space is confirmed by aspirating to ensure no blood or CSF is drawn into the syringe. N.B. Cerebrospinal fluid (CSF) is present in the subarachnoid space but not the epidural space. If the subarachnoid space is entered accidentally, CSF fluid will flow from the hub of the needle. If this occurs the needle may be repositioned without removing it completely. If the patient is in lateral recumbancy the hanging drop technique cannot be used. Instead the ‘pop’ can be felt as the needle penetrates the ligamentum flavum. A test injection of sterile 0.9% saline is usually administered prior to the drug (s). to confirm correct placement. A small air bubble in the syringe can be used to observe any resistance to injection. If resistance is present ( i.e. not in the epidural space), the air bubble would be compressed; if no compression of the air bubble and no resistance to injection, the needle is correctly situated in the epidural space and the drug can be administered. It should be administered slowly over ~ two minutes and the needle then withdrawn.

Question 336

What happens to the affected area after local anaesthetic has been administrated?

Answer 336

If local anaesthetic is introduced, the affected area will be completely anaesthetised due to blockage of nerve transmissions. The patient will temporarily lose sensation (including pain) and motor function to the area. If motor function is lost the patient will be unable to move its hindquarters and will need to be managed as a recumbent patient with appropriate urinary and faecal management until the it has regained function. Urinary retention may occur.

Question 337

What are the side effects of epidural administration?

Answer 337

Prolonged paresis, hypotension, bradyarrhythmias, pruritus and poor hair regrowth are potential side-effects of epidural administration.

Question 338

How can peripheral nerve location be identified?

Answer 338

Peripheral nerve location can be identified using | ultrasound or by using peripheral nerve stimulator.

Question 339

What is the difference between a local and regional nerve block?

Answer 339

If local anaesthetic is infiltrated around a specific nerve e.g. the mandibular nerve the effect will be localised. A mandibular nerve block can be used for dental procedures/ trauma to the rostral mandible. A brachial plexus block, however, is a regional block which provides analgesia to the whole forelimb. Local anaesthetic infiltrated around each of the radial, ulnar, median and musculocutaneous nerves, anaesthetises the elbow and distal forelimb. The whole of the hind limb can be anaesthetised by doing a combination of a sciatic nerve block and femoral nerve block. Whereas if local anaesthetic is infiltrated around the sciatic nerve only, the stifle and distal limb will be anaesthetised, rather than the whole of the hind limb, which can be beneficial depending on the patient’s problem.

Question 340

When would an intercostal nerve block be used?

Answer 340

An intercostal nerve block is a useful adjunctive analgesic for a patient undergoing a thoracotomy.

Question 341

What is an infiltrative block?

Answer 341

The simplest, but least precise, way of providing analgesia to an area is to perform an infiltrative block. Intradermal and subcutaneous infiltration of the region e.g. around a wound can be used to provide local desensitisation. Care must be taken not to exceed the maximum calculated dose, especially in a cat, to avoid toxicity; and accidental intravascular injection must be avoided

Question 342

What is a constant rate infusion?

Answer 342

The term constant rate infusion (CRI) usually refers to the continuous administration of medication to a patient via the intravenous route. However, a CRI may sometimes be used for delivery of nutrients to a patient e.g. jejunostomy tube.

Question 343

What are some reasons for delivering a drug as a constant rate infusion?

Answer 343

There are several reasons for delivering a drug as a CRI – analgesia being the main one. They can also be used for blood pressure management in e.g. patients with sepsis; administration of general anaesthetic e.g. TIVA/ PIVA; administration of insulin in a patient with diabetic ketoacidosis and electrolytes e.g. potassium. The drug may be delivered using a syringe driver/pump or a bag of IV fluids. A patient receiving a CRI requires close, 24-hour monitoring. Delivery of analgesia as a CRI is a titratable method of providing effective pain relief to an ECC patient i.e. the amount administered can be adjusted up or down depending on the patient’s needs. Continuous delivery of medication avoids peaks and troughs in serum drug concentration

Question 344

What drugs are usually used as CRI's?

Answer 344

A CRI can be single agent (e.g. opioid) or may be a combination of different drugs providing a multi-modal approach to analgesia. CRIs that are used for analgesia in ECC patients include fentanyl (single agent); morphine/lidocaine/ketamine combination (MLK), and occasionally subanaesthetic micro doses of medetomidine CRI. Ketamine is an NMDA antagonist which can be administered in combination with other drugs to provide analgesia as a CRI.

Question 345

What are the two types of CRI's?

Answer 345

There are two types of CRI- ➢ Pre- set rate- i.e. fluids running at a constant, pre-set rate e.g. 30 ml/hour ➢ Titratable- fixed concentration of drug (mcg/ml). Dose to the patient depends on the fluid flow rate

Question 346

What do you need to do for a preset method CRI?

Answer 346

PRE-SET RATE METHOD | For this method, the amount of drug to be added to a fixed volume of IV fluids needs to be calculated.

Question 347

Before calculating a pre set method CRI what information is required?

Answer 347

Before starting the following information is required - ➢ Weight of patient (e.g. 20 kg) ➢ Fluid flow rate (e.g. 40 ml/hour) ➢ Size of bag of fluids (e.g. 500 ml) ➢ Concentration of drug (e.g. 3mg/ml) ➢ Dose of drug (e.g.1mg/kg/day, 3 µg/kg/min (0.003mg/kg/hr) or 0.18mg/kg/hr)

Question 348

What calculation is required for doses given in mgs/kg/hr for a preset method CRI?

Answer 348

For dosages given in mgs/kg/hr 1. Set up equation based on dosage • mg/kg/hour = mgs to add to bag 2. Enter weight 3. Calculate number of hours that bag will last • Fluid bag size ÷ hourly rate = #hrs bag will last 4. Solve equation • mg * kg * number of hours bag will last = mgs to add to bag 5. Calculate drug volume to be added to bag • mgs to add to bag / concentration mgs/mL = # of mLs to add to bag.

Question 349

The next card is an example of how to calculate a drug using a preset method CRI?

Answer 349

Example 1: Calculate the volume of drug (50mg/mL) that will need to be added to a bag of saline (250mL) to deliver a dose of 5 mg/kg/hr to a dog weighing 30kg at a rate of 25 mL/hr • Dose = 5 mg/kg/hr • Body weight = 30 kg • Fluid rate that drug will be delivered = 25 mL/hr • Fluid bag size = 250mL • Drug concentration = 50mg/mL 1. Set up equation based on dosage • 5 mg/kg/hour = mgs to add to bag 2. Enter weight • 5*30*hour = mgs to add to bag 3. Calculate number of hours that bag will last • Fluid bag size / hourly rate = #hrs bag will last • 250/25 = 10 hours 4. Solve equation • mg * kg * number of hours bag will last = mgs to add to bag • 5*30*10 = mgs to add to bag = 1500mg 5. Calculate drug volume to be added to bag • mgs to add to bag / concentration mgs /mL = # of mLs to add to bag 1500 / 50 = 30 mL N.B. Some dosages are given in µg/kg/min N.B. There are 1000 µg per mg. An extra step is involved- the fluid rate in minutes will need to be converted from the hourly rates For dosages given in µg/kg/min: 1. Set up equation based on dosage • µg/kg/min = µg to add to bag 2. Enter weight 3. Calculate number of hours that bag will last • Fluid bag size ÷ hourly rate = #hrs bag will last 4. Convert number of hours to minutes • #hrs bag will last * 60 5. Solve equation • µg * kg * number of minutes bag will last = µg to add to bag 6. Convert µg to mg • µg to add to bag / 1000 7. Calculate drug volume to be added to bag • mg to add to bag / concentration mg/mL = # of mLs to add to bag.

Question 350

What is a titratable method for a CRI?

Answer 350

TITRATABLE METHOD ➢ The dose delivered to patient depends on rate of fluid delivery- this needs to be calculated initially. ➢ This CRI is usually administered separately alongside a bag of fluids e.g. syringe driver/ second bag of fluids. ➢ This uses a dose range rather than set dose per hour ➢ The rate of drug delivery can be changed to give patient depending on response ➢ The CRI is calculated so that 1 ml/hour = 1 μg/kg/hour ➢ So if the rate is increased to e.g. 2ml/hour the patient will receive 2 μg/kg/hour etc. ➢ As this usually involves small drug volumes it is usually calculated in micrograms/kg/hour. ➢ A fixed volume is made up depending on the size of syringe e.g. 20 ml/ 60 mls

Question 351

What information is required prior to calculating a CRI using a titratable method?

Answer 351

Before starting the following information is required - ➢ Patient weight (12kg) ➢ Drug strength (e.g. 50 μg/ml) ➢ Syringe size/ bag of fluids size (e.g. 20 ml syringe for syringe driver) ➢ How to calculate to deliver 1 μg/kg/hour.

Question 352

How do you calculate a dose for a CRI using a titratable method?

Answer 352

1. Calculate how much is needed to deliver 1 μg/kg/hour for our patient (12 kg) 2. 1 x bodyweight/ hour = 12 μg/kg/hour 3. Calculate how many μg of drug need to be added to the syringe 4. 20 ml syringe = 20 hours of treatment at 1ml/kg/hr 5. Total number (μg of drug) required for syringe = dose per hour × hours of CRI 6. 12 x 20 = 240 μg of drug 7. Calculate how many mls of drug needed (total number of μg divided by drug concentration μg/ml) 8. 240/40 = 4.8 ml 9. The volume of drug (4.8 ml) should be added to 0.9% saline so that the total volume is the same as the volume of the syringe (20 ml) to ensure 1 μg/kg/hour is delivered. 10.The volume of saline required = size of syringe – volume of drug calculated 11.20 ml - 4.8 ml = 15.2 ml of saline 12.4.8 ml of drug is added to 15.2 ml of saline to make 20 ml

Question 353

What is EMLA cream?

Answer 353

Topical analgesia can be achieved with the product EMLA™ cream that provides full skin (epidermis and dermis) thickness analgesia 5-10 minutes after being applied. It may be used to facilitate catheter placement, allow small wound repair or removal of small skin lesions.

Question 354

What are wound soaker catheters?

Answer 354

Direct introduction of local anaesthetic to wounds using ‘wound soaker catheters’ has recently found favour as a technically easy and well-tolerated way of providing analgesia to veterinary patients. Wound soaker catheters are sutured in place and allow for intermittent or CRI delivery of local anaesthetic to the wound site, without appearing to delay wound healing. This can provide effective analgesia to a patient post-amputation or thoracotomy.

Question 355

Which of the the following is an alpha-2 agonist? Select one: a. Mannitol b. Dexmedetomidine c. Lidocaine d. Meloxicam

Answer 355

(N.B. ensure you are aware of when each of these drugs might be used in an emergency patient; the route(s) of administration, potential side-effects and contraindications) The correct answer is: Dexmedetomidine

Question 356

Which of the following opioids is a partial agonist? Select one: a. Fentanyl b. Pethidine c. Buprenorphine d. Methadone

Answer 356

(N.B. Please ensure you are aware of the mode of action of opioids. Which receptor do they act at? What is meant by potency and efficacy? What are the relative advantages and disadvantages of full and partial agonists? By what routes can opioids be administered?) The correct answer is: Buprenorphine

Question 357

In which clinical scenario is NSAID administration least likely to be associated with serious side-effects? Select one: a. A patient with acute kidney injury b. A patient with haematemesis c. A hypovolaemic patient d. A patient with elbow luxation

Answer 357

( N.B. Please review the mode of action of NSAIDs and ensure you are aware of the potential issues associated with their administration) The correct answer is: A patient with elbow luxation

Question 358

Which of the following anaesthetic protocols could be appropriate for maintaining anaesthesia in a cat undergoing repair of a diaphragmatic rupture? N.B. More than one option could be selected ** Select one or more: a. Nitrous oxide and oxygen b. Halothane and oxygen c. Sevoflurane and oxygen d. TIVA with propofol e. Isoflurane and oxygen f. Alpha 2 agonist and ketamine

Answer 358

( N.B. ensure you are aware of the actions, route of administration and potential side-effects of each drug listed. Consider the advantages and disadvantages of each protocol listed) The correct answers are: Isoflurane and oxygen, Sevoflurane and oxygen