Anaesthetics Flashcards
1
Q
What is the function of a general anaesthetic?
A
- Produces insensibility in the whole body, usually causing unconsciousness
- Centrally acting drugs - hypnotics/analgesics
2
Q
What is the function of a regional anaesthetic?
A
- Producing insensibility in an area/region of the body
- Local anaesthetics applied to nerves/plexuses supplying relevant area
3
Q
What is the function of a local anaesthetic?
A
- Producing insensibility in only the relevant part of the body
- Local anaesthetics applied directly to the tissues
4
Q
What types of anaesthetic drugs exist?
A
Inhalational Intravenous Muscle relaxants Local anaesthetics Analgesics
5
Q
What types of techniques and equipment exist for anaesthesia?
A
Tracheal intubation Ventilation Fluid therapy Regional anaesthesia Monitoring
6
Q
What are the triad components of anaesthetic?
A
Analgesia
Hypnosis
Relaxation
(But does not require all three!)
7
Q
Give an example of an anaesthetic that may consist only of hypnosis?
A
Simple anaesthetic for dental extraction
8
Q
Give an example of an anaesthetic that may consist only of analgesia?
A
Local anaesthetic for dental extraction
9
Q
Give an example of an anaesthetic that may consist only of analgesia and relaxation, with no hypnosis?
A
Spinal anaesthetic
eg Epidural
10
Q
What type of drugs contribute to relaxation in anaesthesia?
A
Local anaesthetics
General anaesthetics
Muscle relaxants
11
Q
What type of drugs contribute to analgesia in anaesthesia?
A
Local anaesthetics
General anaesthetics (minor - except ketamine)
Opiates
12
Q
What type of drugs contribute to hypnosis in anaesthesia?
A
General anaesthetics Opiates
13
Q
What are the advantages of balanced anaesthesia (using different drugs for different jobs)?
A
- Titrate doses separately & therefore more accurately to requirements
- Avoid overdosage
- Enormous flexibility
14
Q
What problems can arise in anaesthetic?
A
- Polypharmacy
- Muscle relaxation (requirement for artificial ventilation)
- Separation of relaxation + hypnosis (Can lead to awareness)
15
Q
What is the mechanism of action of general anaesthetics?
A
- Interfere with neuronal ion channels
- Hyperpolarise neurones = less likely to fire
16
Q
What membrane receptors do intravenous agents have an effect on?
A
GABA receptors
eg Thiopentone/Propofol
17
Q
In what way are functions lost in general anaesthetics?
A
Most complex processes lost first
Primitive functions lost later
18
Q
What are the main component of anaesthetic management?
A
ABC - - long drawn out resus Mandates airway management Impairment of respiratory function and control of breathing Cardiovascular impact Care of the unconscious patient
19
Q
What is arm-brain circulation time?
A
Refers to time taken for drug to get from hand to blood brain barrier
Ie the rapid onset of consciousness in Iv anasethesia
20
Q
Why does IV anaesthesia have a rapid recovery time?
A
- Disappearance of drug from circulation
- Redistribution vs metabolism
21
Q
What type of drugs are used as inhalational anaesthetics?
A
-Halogenated hydrocarbons
22
Q
What measure of potency is used for inhalational anaesthetics?
A
MAC (Minimum Alveolar Concentration)
23
Q
What is the main role of inhalational anaesthetics?
A
Extension/continuation of anaesthesia
24
Q
What is the most common sequence of general anaesthesia?
A
Intravenous induction
->Inhalation maintenance
25
What effects do general anaesthetics have centrally on the cvs?
Depress cardiovascular centre
- reduce sympathetic outflow
- negative inotropic/chronotropic effect on heart
- reduced vasoconstrictor tone → vasodilation
26
What effects do general anaesthetics have directly on the cvs?
-Negatively inotropic
-Vasodilation
→ decreased peripheral resistance
-Venodilation
decreased venous return,
decreased cardiac output
27
What effects do general anaesthetics have on the respiratory system?
All anaesthetic agents are respiratory depressants
- Reduce hypoxic and hypercarbic drive
- Decreased tidal volume & increase resp rate
Paralyse cilia
Decrease FRC
- Lower lung volumes
- VQ mismatch
28
What indications are there for muscle relaxants in anaesthetics?
```
Ventilation & Intubation
When immobility is essential
-microscopic surgery,
-neurosurgery
Body cavity surgery (access)
```
29
What problems are associated with muscle relaxants in general anaesthesia?
- Awareness
- Incomplete reversal →
- Airway obstruction, ventilatory insufficiency in immediate post op period
- Apnoea = dependence on airway & ventilatory support
30
What is the purpose of intraoperative analgesia?
- Prevention of arousal
- Opiates contribute to hypnotic effect of GA
- Suppression of reflex responses to painful stimuli
- e.g. tachycardia , hypertension
31
List some examples of local anaesthetic drugs?
- Lignocaine
- Bupivacaine
- Ropivacaine
32
What are the effects of local/regional anaesthesia?
-Retain awareness / consciousness
-Lack of global effects of GA
-Derangement of CVS physiology
proportional to size of anaesthetised area
-Relative sparing of respiratory function
33
What steps are involved in the process of anaesthesia?
```
Pre-operative Assessment
Preparation
Induction
Maintenance
Emergence
Recovery
Post-operative Care and Pain Management
```
34
Give some examples of drugs used in IV induction of anaesthesia?
Propofol
| Thiopentone
35
Give some examples of a drug used in gas induction of anaesthesia?
Sevoflurane (Halothane)
36
What is used for monitoring consciousness level in anaesthesia?
- Loss of verbal contact
- Movement
- Respiratory Pattern
- Processed EEG
- 'Stage' or 'planes' of anaesthesia
37
What is involved in the triple airway manoeuvre in airway management?
Head Tilt
Chin Lift
Jaw Thrust
38
What simple apparatus may be used in airway maintenance?
- Face mask
- Orophayngeal (Guedel) Airway
- Nasopharyngeal Airway
39
What state does the patient need to be in for insertion of an oropharyngeal (guedel) airway?
Unconsciousness
40
What may be used in more advanced airway management?
Laryngeal Mask Airway
41
What may be used for resuscitation airway management?
i gel Laryngeal airway
42
What are some airway complications?
Obstruction
- Ineffective Triple Airway Manoeuvre
- Airway Device malposition or kinking
- Laryngeal spasm
Aspiration
43
What is the only thing to protect the airway? (Rather than maintain it?)
Endotracheal intubation
| A cuffed tube in the trachea
44
What reasons may you intubate a patient?
- Protect airway from gastric contents
- Need for muscle relaxation: artificial ventilation
- Shared airway with risk of blood contamination (tonisllectomy in ENT)
- Need for tight control of blood gases (eg neurosurgery)
- Restricted access to airway (eg Max-Fax)
45
What risks are there to an unconscious patient?
- Airway maintenance
- Temperature maintenance
- Loss of protective reflexes
- Venous thromboembolism risk
- Consent and identification
- Pressure areas
46
What may be used in the maintenance of anaesthesia?
IV/Inhalational anaesthesia or both
47
What is monitored in anaesthesia?
```
Basic “minimum” monitoring
-SpO2, ECG, NIBP, FiO2, ETCO2
Respiratory parameters
Agent monitoring
Temperature, Urine Output, NMJ
Invasive Venous / Arterial Monitoring
Processed EEG
VENTILATOR DISCONNECT
```
48
What are the risk factors for awareness in anaesthesia?
```
Paralysed and ventilated
Previous episodes of awareness
Chronic CNS depressant use
Major trauma
GA C/Section
Cardiac Surgery
```
49
What happens during emergenece/awakening of anaesthesia?
```
Muscle relaxation reversed
Anaesthetic agents off
Resumption of spontaneous respiration
Return of airway reflexes / control
Extubation
```
50
What is critical care?
-Organ system support (single vs multiple)
| Initial assessment: ABCDE
51
What are the oxygen and carbon dioxide levels in type 1 respiratory failure?
- Oxygen = Low
- Carbon Dioxide = Normal/Low
(Failure of oxygenation)
52
What are the oxygen and carbon dioxide levels in type 2 respiratory failure?
- Oxygen = Low
- Carbon Dioxide = High
(Failure of oxygenation + ventilation)
53
What breathing support systems may be use in respiratory failure?
Heated-humidified high flow therapy
Non-invasive Ventilation
Endotracheal ventilation
54
What is the definition of shock?
Shock is acute circulatory failure with inadequate or inappropriately distributed tissue perfusion resulting in cellular hypoxia
55
List some types of shock
```
Distributive (septic)
Hypovolaemic
Anaphylactic
Neurogenic
Cardiogenic
```
56
What is the formula for working out cardiac output?
HR x Stroke Volume
57
What is stroke volume dependant on?
Preload
Contractility
Afterload
58
What vasopressors are used in cardiovascular failure?
- Metaraminol
| - Noradrenaline
59
What inotropes are used in cardiovascular failure?
- Adrenaline
| - Dobutamine
60
What is the function of inotropes?
Improves contractility in the heart
61
How much fluid is used in maintenance fluid?
30ml/kg over 24 hours
62
What are some potential causes for neurological failure?
- Metabolic causes
- Trauma
- Infection
- Stroke
63
What should be considered in a preoperative assessment for anaesthesia?
```
Patient
-Known co-morbidities
-Unknown pathologies
Nature of surgery
Anaesthetic techniques
Post-op care
Identify high risk - optimise and minimise risk!
```
64
What does pre-operative assessment reduce for the patient?
```
Anxiety
Delays
Cancellations
Complications
Length of stay
Mortality
```
65
What is considered in patient history for a pre-op assessment?
- Known co-morbidities
- Unknown co-morbidities
- Ability to withstand stress
- Drugs and allergies
- Previous surgery and anaesthesia
- Potential anaesthetic problems (Airway, Spine, Reflux etc)
66
What investigations may be used in pre-op assessment in anaesthesia?
Link with patient's comorbidities! Only investigate if it will change management
Cardiovascular
ECG, Exercise tolerance test
Echo, Myocardial perfusion scan, Stress echo, Cardiac catheterisation, CT coronary angiogram
Respiratory
Saturations, ABG, CXR, Peak flow measurements, FVC/FEV, Gas transfer,
CT chest
67
What does ASA1 grading mean?
Otherwise health patient
68
What does ASA2 grading mean?
Mild to moderate systemic disease
69
What does ASA5 grading mean?
Patient on brink of death
70
What risk assessment tools are used in anaesthesia?
Surgical Outcome Risk Tool (SORT)
| POSSUM scoring
71
What conditions may contribute to cardiac risk index?
```
High risk surgery
Ischaemic heart disease
Congestive heart failure
Cerebrovascular disease
Diabetes
Renal failure
```
72
What medical conditions may be optimised prior to surgery?
```
Hypertension
Ischaemic heart disease
Heart failure
Asthma
COPD
Diabetes
Epilepsy
```
73
What does pre-habilitation refer to?
-Improving fitness prior to surgery
| Also consider change in lifestyle factors!
74
What are some medications that may need to discontinue/alter prior to surgery?
Anti-diabetic medication
| Anticoagulants
75
What is pain?
An unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage
76
List some benefits of treating pain for the patient?
Physical
- Improved sleep, better appetite
- Fewer medical complications (e.g. heart attack, pneumonia)
Psychological
- Reduced suffering
- Less depression, anxiety
77
In what ways can pain be classified?
Acute vs chronic
| Nociceptive vs Neuropathic
78
What are the features of nociceptive pain?
```
Obvious tissue injury or illness
Also called physiological or inflammatory pain
Protective function
Description
-Sharp ± dull
-Well localised
```
79
What are the features of neuropathic pain?
```
Nervous system damage or abnormality
Tissue injury may not be obvious
Does not have a protective function
Description
-Burning, shooting ± numbness, pins and needles
-Not well localised
```
80
Give examples of chemicals that will activate nociceptors?
- Prostaglandins
| - Substance P
81
What nerve fibres transmit pain?
A(delta) or C fibres
82
Where do nerve fibres transmitting pain first synapse?
Dorsal horn
| At this level of spinal cord, second nerve crosses to contralateral side
83
Where is the relay station of pain signalling within the brain?
Thalamus
| Projections to cortex, Limbic system, Brainstem
84
Where does pain perception occur?
In the cortex
85
Where does modulation of pain occur?
- Descending pathway from brain to dorsal horn
| - Location of Gate Theory (Distractive stimulus dampens down signal)
86
Give some examples of neuropathic pain?
- Nerve trauma, diabetic pain (Due to damage)
| - Fibromyalgia, chronic tension headache (Due to dysfunction)
87
What are some pathological mechanisms of pain?
```
Increased receptor numbers
Abnormal sensitisation of nerves
-Peripheral
-Central
Chemical changes in the dorsal horn
Loss of normal inhibitory modulation
```
88
What simple analegesics are used in treatment of pain?
Paracetamol (acetaminophen)
Non-Steroidal Anti-inflammatory drugs
-Diclofenac, ibuprofen
89
What opioid medications are used in pain relief?
Mild
-Codeine, Dihydrocodeine,
Strong
-Morphine, Oxycodone, Fentanyl
90
Other than simple analgesics and opioids, list medications used in pain relief?
- Tramadol ( Mixed opiate and 5HT/NA reuptake inhibitor)
- Nefopam ( NMDA R antagonist, 5HT/NA reuptake inhibitor)
- Antidepressants (e.g. amitriptyline, duloxetine)
- Anticonvulsants (e.g. gabapentin)
- Ketamine (NMDA Receptor antagonist)
- Local anaesthetics
- Topical agents (e.g. Capsaicin)
91
What non-drug treatments are used in pain relief?
```
Rest, Ice, Compression, Elevation
Acupuncture
Massage
TENS
Psychological
```
92
What is the disadvantage of paracetamol?
Liver damage in overdose
93
What is the disadvantage of NSAID drugs?
Gastrointestinal and renal side effects
| Bronchospasm in sensitive asthmatics
94
What are the disadvantages of Codeine?
- Constipation
| - Not good for chronic pain
95
What are the advantages of morphine?
```
Cheap, generally safe
Can be given orally, IV, IM, SC
Effective if given regularly
Good for:
-Mod-severe acute nociceptive pain (e.g. post-op pain)
-Chronic cancer pain
```
96
What are the disadvantages of morphine?
Constipation
Respiratory depression in high dose
Misunderstandings about addiction
Controlled drug
Oral dose is 2-3 times IV / IM / SC dose
97
What type of pain is amitryptiline useful for?
Neuropathic pain
98
What are the disadvantages of amitryptiline?
Anti-cholinergic side effects
99
List some examples of anticonvulsant drugs?
Carbamazepine
Sodium Valproate
Gabapentin
100
What system should be used for nociceptive pain?
The WHO pain ladder
101
What is the RAT approach to pain management?
Recognise
Assess
Treat
102
What is used in pain assessment?
```
Verbal Rating Score
Numerical Rating Score
Visual Analogue Scale
Smiling faces
Abbey Pain Scale (for confused patients)
Functional Pain
```
103
List the steps of the WHP pain ladder for nociceptive pain
Mild
Paracetamol (± NSAIDs)
Moderate
Paracetamol (± NSAIDs) + codeine/ alternative
Severe
Paracetamol (± NSAIDs) + morphine
(Start at the bottom - except if unbearably severe pain!)
As pain resolves, move down a step in the ladder
104
What drugs may be used in the treatment of neuropathic pain?
Amitriptylline
Gabapentin
Duloxetine
105
What is osmolarity?
Measure of solute concentration per unit volume of solvent
106
What is osmolality?
Measure of solute concentration per unit mass of solvent
107
What is tonicity?
Measure of osmotic pressure gradient between two solutions
108
What fraction of fluid in the average person is intracellular?
2/3
109
What fraction of fluid in the average person is extracellular?
1/3
| Of which 20% is intravascular
110
Is there more potassium inside or outside cells?
Inside cells
111
Is there more sodium inside or outside cells?
Outside cells
112
What is the osmolality of cells in the body?
285-290 mOsm/Kg
113
What can be used to assess fluid balance?
History – eg thirst
Examination – Cap. Refill, BP, Vital signs, Skin turgor, weight.
Investigations - Oesophageal Doppler, Pulmonary artery catheter, IVC collapsibility
114
How may a hypovolaemic patient present?
```
Feels nauseous, thirsty
Flat veins
Cool peripheries
No sweat
Low or postural BP and high HR/RR
Concentrate oliguria
May respond to passive leg raise
```
115
What is needed for a hypovolaemic patient?
Resuscitation fluids
| Rehydration fluids
116
How may a hypervolemic patient present?
```
Feels breathless, not thirsty
Veins distended
Warm and oedematous extremities
May have inspiratory crackles
Sweaty
High BP and High HR
High JVP
Dilute urine (could be oliguric or polyuric)
```
117
What is needed for a hypervolemic patient?
No more fluids!
Possibly diuretics (if respiratory compromise)
Haemofiltration (if anuric)
118
What should be recorded in fluid gains and losses?
```
Catheters, drains
Input charts
Vomit bowls
Sputum Pots
Stool charts and stoma losses
```
119
When should resuscitation fluids be given to a patient?
IV fluids urgently to restore circulation with hypovolaemia
| -Severe dehydration, sepsis or haemorrhage leading to hypovolaemia + hypotension
120
When should routine maintenance fluids be given to a patient?
IV fluids if cannot take orally or enterally to meet patient maintenance requirements
121
When should replacement fluids be given to a patient?
IV ADDITIONAL to maintenance to correct existing deficit or ongoing abnormal EXTERNAL losses e.g. diarrhoea, fever
122
When should redistribution fluids be given to a patient?
Abnormal INTERNAL fluid redistribution or abnormal fluid handling, particularly with sepsis, or major illness, cardiac, liver or renal disease e.g. tissue oedema, GI tract/ thoracic / peritoneal collection
123
What is the formula for osmolarity?
2([na+] + [k+]) + urea + glucose
124
What does hypotonicity do to cells?
Cell swelling
125
What does hypertonicity do to cells?
Cellular dehydration
126
What are some symptoms of tonicity changes?
Swelling (Raised ICP, Compromised CBF and herniation)
| Shrinkage (ICH Venous sinous thrombosis)
127
Where would colloid fluids stay within the body once administered?
Intravascular space
128
List some types of crystalloid fluids
```
5% dextrose
0.9% saline
Hartmann’s solution
Plasma-lyte
5th “normal saline” in 4% dextrose
(0.18% saline/4% dextrose)
```
129
List some types of colloid fluids
```
Gelatins
Starches
Dextrans
Albumin
Blood Products
```
130
In what situations may colloids be used?
Anaphylaxis
Coagulopathy
Renal Failure
Rheology
131
What is the sodium content of 0.9% NaCl?
154 Mmol/L
| 10% more than ECF
132
What can be caused by excess administration of 0.9% NaCl?
Hyperchloraemic acidosis (Excess chloride!) -> Decreased Renal Blood flow, Decreased GFR
->> Exacerbates sodium retention
133
How much fluid is given as maintenance fluid?
-30ml/kg/24 hours
134
Why should you never give over 100ml/hr of fluids?
Risk of hyponatreaemia
135
Which fluid should be given for maintenance fluids?
0. 18% NaCl/4% Glucose/0.3% KCL (40mmol/L KCL) at correct rate!!
- UNLESS K>5, NA <132
136
What maintenance fluids should be given for maintenance if K>5.0?
0.18% NaCL/4% Glucose
| Doesnt contain KCL
137
What maintenance fluids should be given for maintenance if Na<132?
Plasmalyte 148
138
How much fluid should be given in replacement fluids?
Equivalent to losses in the last 24 hours
139
Which fluid is given in replacement fluid prescription?
Plasmalyte 148
(Except for upper GI losses - 0.9% NaCl with KCL
-Usually the only indication for 0.9% Saline)
140
What should be given in resuscitation fluids?
Fluid challenge 250-500ml over 5-15 minutes and reassess
-Fluid = Plasmalyte 148/Colloid/Blood
141
What are the 5Rs of fluid therapy?
```
Resuscitation
Routine maintenance
Replacement
Redistribution
Reassessment
```
