Revision - Anaesthetics Flashcards
What does fasting for an operation typically include?
1) 6 hours of no food or feeds before the operation
2) 2 hours of no clear fluids (‘nil by mouth’)
Medications are given before the patient is put under a general anaesthetic.
What may these include?
1) Benzos e.g. midazolam
2) Opiates e.g. fentanyl/alfentanyl
3) A2 agonists e.g. clonidine
Purpose of opiates prior to GA?
1) analgesia
2) reduce hypertensive response to laryngoscope
Give an example of an alpha-2-adrenergic agonist used prior to general anaesthetic
Clonidine
What is the triad of general anaesthesia?
1) Analgesia
2) Muscle relaxation
3) Hypnotics (make patient unconscious)
What is the most commonly used IV hyponotic agent?
Propofol
What is the most commonly used inhaled hypnotic agent?
Sevoflurane
Give 4 options for IV hypnotic agents
1) propofol
2) ketamine
3) thiopental sodium
4) etomidate
Give 4 options for inhaled hypnotic agents
1) Sevoflurane
2) Desflurane (less favourable as bad for the environment)
3) Isoflurane (rarely used)
4) Nitrous oxide (combined with other anaesthetic medications – may be used for gas induction in children)
Sevoflurane, desflurane and isoflurane are volatile anaesthetic agents.
What does this mean?
They are LIQUID at room temperature.
Need to be vaporised into a gas to be inhaled.
IV vs inhaled hyponotics for induction vs maintenance?
IV –> better for induction (quicker onset)
Inhaled –> better for maintenance
What does total IV anaesthesia (TIVA) involve?
IV medication for induction and maintenance of GA.
What is the most commonly used agent for TIVA?
Propofol
Benefit of TIVA over inhaled options?
Can give a nicer recovery as they wake up compared with inhaled options.
Indications for propofol? (2)
1) Induction agent
2) ICU for ventilated patients
Mechanism of propofol?
1) Decreases the rate of dissociation of GABA from its receptor
2) Which increases the duration of the GABA-activated opening of the chloride channel
3) Leads to hyperpolarisation of cell membranes
4) Increased inhibitory tone in the CNS
2 key adverse effects of propofol?
1) Pain on injection
2) Hypotension (marked drop in BP)
What is a benefit of propofol?
Antiemetic –> useful in patients at high risk of PONV
What type of drug is thiopental?
barbiturate
Main side effect of thiopental?
Laryngospasm
Benefit of thiopental?
It is very lipid-soluble so affects the brain quickly i.e. mainly used for RSI
One of the ways that anaesthetic drugs work is by opening K+ channels.
How does this cause an anaesthetic effect?
Reduces membrane excitability –> will lead to more negative resting potential, making it more difficult to start an action potential.
2 main side effects of etomidate?
1) 1ary adrenal suppression
2) Myoclonus
How does etomidate cause 1ary adrenal suppression?
Reversably inhibits 11β-hydroxylase
When is etomidate typically used? Why?
Normally in cases of haemodynamic instability –> causes LESS hypotension than propofol and thiopental during induction.
I.e. mainly used in Cardiac patients Induction (Hemodynamic stability).
Mechanism of ketamine?
Blocks NMDA (glutamate) receptors –> glutamate is the 1ary excitatory neurotransmitter.
When is ketamine favoured as an anaesthetic? Why?
1) In patients with unknown medical history
2) In the treatment of burn victims
3) Trauma
As doesn’t cause a drop in blood pressure or depress breathing and circulation as much as other anesthetics.
Which general anaesthetic has a side effect of laryngospasm?
Thiopental
Which general anaesthetic has a side effect of pain on injection?
Propofol
Which general anaesthetic has a side effect of 1ary adrenal suppression?
Etomidate
Upon entering the anaesthetic room/theatre, the patient will undergo safety checks and have essential monitoring attached.
This can vary according to the procedure, but at a minimum what does it include? (5)
1) ECG
2) O2 sats
3) BP
4) Depth of anaesthesia monitoring
5) Capnography
What are the 2 types of airway management of general anaesthesia?
1) ET
2) SGA e.g. LMA (patient breathes on their own)
Contraindications to SGA?
1) higher risk of reflux e.g. pregnant women, unfasted
2) laparoscopic surgery
3) prone positioning surgery
4) obesity
5) sugery in the nose or mouth
What is the most common problem with SGA placement?
What happens if this occurs?
That the device does not fit or seal well enough to deliver adequate amounts of anesthetic gases and oxygen.
In this situation, the SGA is removed and an endotracheal tube is placed.
If a patient is considered at high risk of airway soiling, what can be used?
RSI
What are 2 causes of malignant hyperthermia?
1) Inhaled volatile agents e.g. sevoflurane
2) Suxamethonium (depolarising muscle relaxant)
What mutation is most commonly involved in cases of malignant hyperthermia?
Autosomal dominant mutation in the ryanodine receptor 1.
How does a mutation in the ryanodine receptor 1 cause malignant hyperthermia?
This results in an abnormality in calcium regulation within muscle cells –> leads to increased calcium levels in the sarcoplasmic reticulum and a consequent increase in metabolic rate.
Signs and symptoms of malignant hyperthermia?
1) rapid increase in body temp
2) muscle rigidity
3) metabolic acidosis
4) tachycardia
5) increased exhaled CO2
How does exhaled CO2 change in malignant hyperthermia?
There is an increase in exhaled CO2
Give 3 differentials for malignant hyperthermia
1) NMS
2) Serotonin syndrome
3) Sepsis
How are CK levels affected in malignant hyperthermia?
Increased
Management of malignant hyperthermia?
1) Immediate discontinuation of the triggering agent.
2) IV dantrolone
3) Restoration of normothermia
4) Correction of acidosis and electrolyte abnormalities.
5) Supportive e.g. oxygen, ventilation etc
Mechanism of IV dantrolene in malignant hyperthermia?
Ryanodine receptor ANTagonist –> helps to decrease intracellular calcium conc & reduce muscle metabolism.
How can the restoration of normothermia be achieved in malignant hyperthermia?
Cooling techniques such as ice packs, cool intravenous fluids, and cooling blankets.
In what situations should nitrous oxide be avoided in?
E.g. pneumothorax –> may diffuse into gas-filled body compartments and cause an increase in pressure
Which general anaesthetic may cause marked myocardial depression?
Sodium thiopentone
Which general anaesthetic is a suitable agent for anaesthesia in those who are haemodynamically unstable?
Ketamine
Which general anaesthetic is post-op vomiting common in?
Etomidate
Purpose of muscle relaxants in general anaesthetics?
They facilitate intubation and improve surgical access (particularly abdominal and laparoscopic procedures).
Give 2 muscle relaxant agents
1) Suxamethonium
2) Rocuronium
What does a simple general anaesthetic induction ‘recipe’ for tracheal intubation in a fit and well patient usually incorporate?
A quick acting opioid (e.g. fentanyl) + propofol
How is tube placement within the trachea confirmed (i.e. what are the 3 essential checks)?
1) Symmetrical chest wall movement
2) Misting within the tube
3) More than 5 waveforms on capnography
These are confirmed whilst delivering 5 test breaths.
How many test breaths are delivered whilst confirming tube placement within the trachea?
5
What is TIVA usually a combination of?
Anaesthetic agent (e.g. propofol) plus a rapid-acting opioid such as remifentanil.
What are 2 advantages of TIVA?
1) improved recovery profile
2) reduced greenhouse gas emissions
What intraoperative monitoring is required?
1) Continuous monitoring of vital signs: blood pressure, heart rate, oxygen saturation, and end-tidal CO2 (capnography).
2) Depth of anaesthesia monitoring
3) Neuromuscular blockade assessment
How is the depth of anaesthesia typically measured?
Give 2 options
1) Using a bispectral index (BIS) monitor
2) Mean alveolar concentration (MAC)
What does a BIS monitor analyse?
Brain’s electrical activity (EEG)
When can MAC be used to measure the depth of anaesthesia?
If volatile agents are used in maintenance
How can the degree of the neuromuscular blockade be assessed?
Using a peripheral nerve stimulator
Where are the leads typically over in a peripheral nerve stimulator?
Facial or ulnar nerve
Cause of hypotension with standard general anaesthetics?
Due to the potent vasodilator effects of most inducation agents (except ketamine and etomidate).
Which 2 general anaesthetics do NOT have potent vasodilator effects?
1) ketamine
2) etomidate
What drugs can be to increase HR during surgery?
Antimuscarinics –> glycopyrronium, atropine
If this fails –> adrenaline
How do muscle relaxants work?
Block the NMJ from working:
Acetylcholine (the neurotransmitter) is released by the axon but is blocked from stimulating a response from the muscle.
What are the 2 categories of muscle relaxants?
1) Depolarising e.g. suxamethonium
2) Non-depolarising e.g. rocuronium
What class of medication can reverse the effects of neuromuscular blocking medications?
Cholinesterase inhibitors e.g. neostigmine
Give an example of a cholinesterase inhibitor
Neostigmine
What medication is used specifically to reverse the effects of certain NON-depolarising muscle relaxants (rocuronium and vecuronium)?
Sugammadex
What are 3 common antiemetics given for prophylaxis given at the end of the operation?
1) ondansetron
2) dexamethasone
3) cyclizine
Who is ondansetron avoided in?
Patients at risk of prolonged QT
Mechanism of cyclizine?
H1 receptor antagonist
Who cyclizine be used with caution in?
HF & elderly
What needs to have worn off before waking the patient during general anaesthetics?
Muscle relaxant
What can be used to determine whether the muscle relaxants have worn off?
Nerve stimulator
What is involved in testing the facial nerve with nerve stimulators?
This involves a train-of-four (TOF) stimulation.
This is where the nerve is stimulated 4 times to see if the muscle responses remain strong (indicating it has worn off) or whether they get weaker with additional stimulation (indicating it has not fully worn off).
What result of train-of-four (TOF) stimulation indicates that muscle relaxants haven’t fully worn off?
Muscle response gets weaker with additional stimulation
What is the main contraindication for thiopentone?
Porphyria
How does ketamine affect BP & HR?
Increased HR & BP
How long do induction agents typically last?
4-10 minutes
What is MAC?
It is defined as the minimum alveolar concentration of inhaled anaesthetic at which 50% of people do not move in response to a noxious stimulus.
Which inhalational agent is sweet smelling?
Isoflurane
Which inhalational agent has the max greenhouse effect?
Desflurane
Which inhalational agent has the least effect on organ blood flow?
Isoflurane –> used in organ donation
Adverse effects of suxamethonium?
1) muscle pains
2) fasciculations
3) hyperkalaemia
4) malignant hyperthermia
5) raised in ICP, IOP & gastric pressure (contraindicated in glaucoma)
What is used to reverse non-depolarising muscle relaxants?
Neostigmine & glycopyrrolate
Which opioid can be used with morphine?
Tramadol
What is the minimum monitoring required during regional anaesthesia?
1) ECG
2) BP
3) O2
Should continue for 30 mins after completion of procedure.
What are the 4 types of regional anaesthetia?
1) Central neuraxial blocks (CNB)
2) Peripheral nerve blocks (PNB)
3) IV regional anaesthesia (IVRA)
4) Topical and infiltration analgesia
What does CNB involve?
Placement of local anaesthetics around the nerves of the CNS.
Give 3 examples of CNB
1) spinal anaesthesia
2) caudal anaesthesia
3) epidural anaesthesia
What type of regional anaesthesia is an epidural?
CNB (central neuraxial block)
What does PNB involve?
Placement of local anaesthetics onto or near the peripheral nerves
What does IVRA involve?
Injection of local anaesthetics into an exsanguinated limb distal to an occluding tourniquet.
What 2 approaches can be used for a CNB?
1) Midline
2) Paramedian
What are 3 common examples when a CNB is used?
1) Caesarean section
2) Hip fracture repairs
3) TURP
Into what space is anaesthetic injected in spinal anaesthesia?
Subarachnoid (into the CSF)
What structures does the needle pass through in spinal anaesthesia?
skin
soft tissue
spinal ligaments (‘pop’ of ligamentum flavum)
dura mater
What are the 3 spinal ligaments?
1) supraspinous ligament (outside)
2) interspinous ligament (middle)
3) ligamentum flavum (inside)
What level is the needle inserted in spinal anaesthesia?
L3/4 or L4/5 (below the termination of the spinal cord)
At what level does the spinal cord noramlly terminate?
L1/2
Where will neuraxial anaesthesia will cause numbness and paralysis?
In the areas innervated by the spinal nerves BELOW the level of the injection.
What can be used to test whether the spinal anaesthetic has worked?
Cold spray
How are local anaesthetics used for spinal anaesthesia altered?
Made hyperbaric (denser than CSF) by adding dextrose
Purpose of local anaesthetics used for spinal anaesthesia being hyperbaric?
1) hyperbaric solutions have a greater spread in the direction of gravity
2) more predictable with minimal inter-patient variability
How long does a single-injection spinal anaesthesia last?
2-3 hours (unsuitable for prolonged surgeries).
What structures does the needle pass through in epidural anaesthesia?
Skin
Soft tissue/fat
Supraspinous ligament
Interspinous ligament
Ligamentum flavum
Note - does NOT pass through dura mater (unlike spinal anaesthesia)
What happens in an epidural?
1) Catheter is inserted into epidural space
2) Local anaesthetic medications are infused through the catheter into the epidural space, where they diffuse to the surrounding tissues and spinal nerve roots
What drug is often used in epidural anaesthesia?
Levobupivacaine +/- fentanyl
Give some adverse effects of epidural anaesthesia
1) headache if dura is punctured (PDPH)
2) hypotension & bradycardia
3) motor weakness in legs
4) nerve damage
5) haematoma (may compress spinal cord)
6) infection, including meningitis
When used for analgesia in labour, what are the risks in epidural anaesthesia?
1) prolonged 2nd stage of labour
2) increased risk of instrumental delivery
Patients need an urgent anaesthetic review if they develop significant motor weakness (unable to straight leg raise) after an epidural.
What does this indicate?
The catheter may be incorrectly sited in the subarachnoid space (and cerebrospinal fluid) rather than the epidural space.
What are the major risk factors for hypotension in epidural anaesthesia?
Extent and onset of sensory block –> faster onset and more extensive block usually increase the probability of hypotension.
What are the 3 most commonly used vasopressors for managing hypotension associated with neuraxial anaesthesia?
1) metraminol
2) ephedrine
3) phenylephrine
What is the caudal space?
An extension of the epidural space
Who are caudal anaesthesia and analgesia more useful in?
Paeds
What must be available when performing regional anaesthesia?
where there are facilities available to quickly induce a general anaesthetic if it is not effective or the patient starts to experience pain.
What do brachial plexus blocks ABOVE the clavicle target?
The ventral rami, trunks & divisions
What do brachial plexus blocks BELOW the clavicle target?
Cords & terminal nerves
What type of peripheral nerve block is used for shoulder surgeries?
Interscalene block
What type of peripheral nerve block is used for elbow operations?
Supraclavicular
What type of peripheral nerve block is used for forearm operations?
Infraclavicular
What type of peripheral nerve block is used for hand operations?
Axillary
Which nerve block is mostly performed to provide analgesia following rib fractures and thoracic surgery?
Intercostal nerve block
What are some complications of supraclavicular upper limb blocks?
1) pneumothorax
2) ipsilateral phrenic nerve
3) recurrent laryngeal nerve palsy
What is a complication of an intercostal block?
Pneumothorax
What are some complications of a femoral nerve blocks?
vascular injury leading to haematoma and arterial pseudoaneurysm
Mechanism of local anaesthetic drugs?
They reversibly block sodium channels on the neuronal membrane –> this blocks the conduction of impulses –> produces a reversible loss of motor power and sensory sensation.
What can be added to local anaesthetic solutations?
Why?
Adrenaline:
- reduce blood flow
- decrease drug uptake
- prolong action
When should adrenaline AVOID being added to local anaesthetic solutions?
Why?
For blocks of digits or penis –> risk of tissue ischaemia
Which local anaesthetic has the fastest onset?
Lidocaine
What are 2 risk factors for lidocaine toxicity?
1) hepatic dysfunction
2) low protein state
Why is a low protein state a risk factor for lidocaine toxicity?
As lidocaine is protein bound
Where does the subarachnoid space end?
S1
Where does the epidural space end?
Sacrococcygeal hiatus
What level is epidural done for a laparotomy?
Thoracic level
At what level is there risk of damage to the cord in an epidural?
> L1
What is the safe dose for Lignocaine without adrenaline?
3mg/kg
What is the safe dose for Lignocaine with adrenaline?
7mg/kg
What is the safe dose for bupivacaine?
2mg/kg
What does % mean in local anaesthetics?
1% = 100 mg/100ml (1g/100ml)
What are the signs of local anaesthetics systemic toxicity?
1) Excitatory signs:
- circumoral numbness (earliest)
- tongue paraesthesia
- dizziness
- restlessness and agitation followed by CNS depression (slurred speech, drowsiness, unconsciousness) and/or sudden alteration in mental status, agitation or loss of consciousness
2) Muscle twitching leading to tonic-clonic seizures
3) Respiratory arrest
4) Cardiac arrhythmias: sinus bradycardia, conduction blocks, ventricular tachy-arrhythmias & Asystole
Mx of local anaesthetic toxicity?
IV lipid emulsion
1) Stop injecting the LA
2) Call for help
3) Maintain the airway
4) Give 100% oxygen and ensure adequate lung ventilation
5) Confirm or establish intravenous access
6) Control seizures: use benzodiazepine, thiopental or propofol in small incremental doses
7) Assess cardiovascular status throughout and treat arrhythmias or arrest as per ALS protocol
8) Give intravenous lipid emulsion
What location of RA can cause ipsilateral phrenic nerve palsy?
Supraclavicular upper limb block
Presentation of ipsilateral phrenic nerve palsy?
SOB
Presentation of bronchospasm and laryngospasm?
- hypoxia
- increased CO2
- reduced ventilation
- wheeze (bronchospasm)
- high pitched stridor (laryngospasm)
Clinical features of aspiration of gastric contents in GA?
- bronchospasm
- laryngospasm
- hypoxia
- pneumonia
How may injury to the trachea, bronchial structures or alveoli following an episode of anaesthesia present?
SC emphysema or pneumothorax
N.B. Pneumothorax may also result from the rupture of pre-existing bullae.
When may pulmonary oedema occur in GA?
May occur following laryngospasm or airway obstruction, especially during the recovery phase from anaesthesia.
Inspiratory effort against the closed glottis leads to excessive negative pressure within the alveoli resulting in pulmonary oedema.
When should you suspected pulmonary oedema after GA?
Suspect in patients with hypoxia following laryngospasm
Presentatin of pulmonary oedema in GA?
1) hypoxia following laryngospasm
2) fine bi-basal crepitations
What condition may worsen pharyngeal obstruction in GA?
Obstructive sleep apnoea
How can pharyngeal obstruction be identified?
Snoring
Management of pharyngeal obstruction?
1) basic airway manoeuvres
2) place patient in lateral position
3) overnight CPAP may be required following a general anaesthetic.
AKI is a common complication in the post-op period.
How may it present?
1) Reduced urine output
2) Worsening of metabolic parameters (e.g. acid-base balance and electrolyte imbalance)
What type of anaesthesia is a higher risk of urinary retention?
Spinal
What metabolic disturbance can contribute to post-op ileus?
Hyperkalaemia
What is postoperative cognitive dysfunction (POCD)?
A decline in cognition apparent after a patient recovers from the acute impact of surgery and hospital stay.
May present as acute delirium or be more subtle (e.g. memory impairment, difficulty comprehending etc.).
Inadvertent perioperative hypothermia (IPH) is a common consequence of general and regional anaesthesia.
What is IPH defined as?
Core temp <36 degrees
Adverse effects of IPH?
1) surgical site infection
2) coagulopathy
3) increased transfusion requirements
4) pain
5) altered drug metabolism
6) adverse cardiac events
Preventative measures to avoid IPH?
1) Keeping patients warm during the pre-operative phase
2) Active warming during the intraoperative phase with fluid warmers and forced air warming blankets
3) Keeping the patient covered during the recovery
When does PDPH typically occur?
72h after dural puncture
Management of PDPH?
1) refer to anaesthetic team
2) exclude other causes of acute headache
3) bed rest
4) adequate hydration
5) avoiding situations which would give rise to an increase in intracranial pressure
6) simple analgesics
7) epidural blood patch: can be performed if headache persists
An anaesthetic breathing circuit contains a reservoir bag.
What is this for (2 reasons)?
1) for monitoring the patient’s respiration and ventilating the patient if required
2) also acts as a gas reservoir, protecting the patient from excessively high pressures within the breathing system.
How is carbon dioxide removed from the breathing system?
As the ‘circle system’ requires re-breathing of expired gases, carbon dioxide is actively removed from the circuit via a soda lime canister.
What methods are used to monitor temp in anaesthetics?
(2)
1) tympanic thermometer
2) oesophageal probes
What does ‘thermoregulation in the perioperative period’ refer to?
The temp management of patients from 1h before surgery to 24h after
Risk factors for perioperative hypothermia?
1) ASA grade ≥2
2) Large volumes of unwarmed IV transfusions
3) Major surgery
4) Low BMI
Define the pre-operative phase
Starting 1h before induction of anaesthesia
The patient’s temperature should be measured in the pre-operative phase.
What should you do if:
a) patient’s temp is <36 degrees
b) >/= 36 degrees
a) commence active warming
b) acceptable to start warming 30 minutes prior to anaesthetic induction
Should patients be moved to the theatre suite if their temperature is less than 36.0ºC?
No - unless they have a time critical condition that requires urgent management.
At what volume should IV fluids be warmed prior to administration?
> 500ml (as should all blood products)
What is intra-operative hyperthermia typically due to?
Overwarming
How can perioperative hypothermia cause coagulopathy?
Hypothermia reduces blood’s ability to clot, causing increased intra-operative blood loss.
How can perioperative hypothermia cause prolonged recovery from anaesthesia?
Small decreases in body temperature can cause drastic prolongation of anaesthetic drugs, both neuromuscular blocking agents, propofol and inhalational agents.
How can peri-operative hypothermia cause reduced wound healing?
Hypothermia leads to local vasoconstriction which reduces perfusion to the skin, this reduces the necessary immune moderators available at the site to promote healing.
What are the dangers of shivering (a complication of perioperative hypothermia)?
It can cause a significant increase in metabolic rate which can in certain patient groups even result in myocardial ischaemia.
What is laryngospasm?
The complete or partial reflex adduction of the vocal cords due to the involuntary contraction of the intrinsic muscle of the larynx.
What are some anaesthetic-related risk factors that can increase the risk of laryngospasm?
1) Insufficient depth of anaesthesia
2) Mucous or blood in the peri-glottic area
3) Airway manipulation (laryngoscopy, suction)
What are some patient-related risk factors that can increase the risk of laryngospasm?
1) Age (young children at greatest risk)
2) Airway hyperactivity (asthma, smokers)
3) Recent upper respiratory tract infection (up to 6 weeks prior)
4) GORD
Management of laryngospasm?
1) Removal of the stimulus (e.g. removal of blood clots by suctioning, removal of supraglottic airway device)
2) Calling for senior anaesthetic help
3) 100% FiO2, high-flow oxygen using a face mask
4) Application of positive end-expiratory pressure (PEEP)
5) Deepening of anaesthesia with propofol
If the above measures do not work, patients will require suxamethonium (a depolarising muscle relaxant) to relax the vocal cords and endotracheal intubation.
What is a common cause of local anaesthetic toxicity?
Accidental intravascular injection of LA
What site of LA is most likely to result in LA toxicity?
Intercostal block (highly vascularised area)
Described stages 1-6 of the ASA
I - normal, healthy patient
II - mild systemic disease (e.g. asthma), smoker, drinker
III - severe systemic disease
IV - severe systemic that is constant threat to life
V - moribund patient (not expected to survive without operation, e.g. ruptured AAA)
VI - braindead, organ removal for donation purposes
What is suxamethonium apnoea?
A deficiency in enzymes required to break down suxamethonium, resulting in prolonged paralysis of skeletal muscle.
What should you SPECIFICALLY ask about when discussing allergies & intolerances in pre-op assessment?
Penicillin & NSAIDs
What should you SPECIFICALLY ask about when discussing medication history in POA?
1) anticoagulants
2) antihypertensives
3) COCP
4) antiplatelets
5) analgesics
Purpose of Wilson’s score?
Used in assessing the physical characteristics in order to predict the how difficult endotracheal intubation will be.
What Wilson’s score suggests easy laryngoscopy?
<5
What Wilson’s score suggests potentially difficult laryngoscopy?
5-8
What Wilson’s score suggests indicates a risk of severe difficulty in laryngoscopy?
8-10
What score is used to predict the ease of endotracheal intubation?
Mallampati score
What does the Mallampati test comprise?
The test comprises a visual assessment of the distance from the tongue base to the roof of the mouth, and therefore the amount of space in which there is to work.
Does warfarin need to be stopped prior to surgery?
If minor superficial surgery e.g. ophthalmic or minor dental procedures) –> NO
For all other surgeries –> the last dose of warfarin should be given 6 days before the procedure.
When should warfarin be stopped prior to surgery?
6 days
How soon before a neuraxial block should heparin be stopped?
4 hours before (with evidence of a normal APTT)
Following “prophylactic dose LMWH”, how long must you wait before performing a neuraxial block?
12h
Following “treatment dose LMWH”, how long must you wait before performing a neuraxial block?
24h
Which antiplatelet must be stopped before surgery and/or neuraxial intervention?
Clopidogrel
When should clopidogrel be stopped prior to surgery? Why?
7 days before
Clopidogrel causes irreversible platelet inhibition
When should ACEi be stopped prior to surgery?
Withheld on the morning of surgery
When should beta blockers be stopped prior to surgery?
Continued as normal
What tests do patients on digoxin require prior to surgery?
ECG & bloods to rule out hypokalaemia
Should oral hypoglycaemic agents such as metformin be stopped prior to surgery?
Should be omitted on day of surgery
When should diabetic patients be considered for insulin-dextrose sliding scale therapy during the perioperative period?
Diabetic patients that will be missing more than one meal due to fasting and operative time
Which patients will need supplementary steroids during the perioperative period?
Patients who take more than 5mg prednisolone daily
Under what circumstances should an ECG be performed in the pre-op period?
1) >80 y/o
2) >60y/o and surgical severity >3
3) Cardiovascular or renal disease
When should a pregnancy test be performed in the pre-op period?
ALL women of reproductive age
What BP is required prior to operation?
The patient’s BP needs to be 160/100 mmHg or lower in the community prior to the operation.
How should metformin be altered prior to surgery?
Day prior –> take as normal
Day of (morning operation):
- If taken once or twice a day - take as normal
- If taken three times per day, omit lunchtime dose
Day of (afternoon operation):
- If taken once or twice a day – take as normal
- If taken three times per day, omit lunchtime dose
How should sulfonylureas be altered prior to surgery?
Day prior –> take as normal
Day of (morning op):
- If taken once daily in the morning - omit the dose that day
- If taken twice daily - omit the morning dose that day
Day of (afternoon op):
- If taken once daily in the morning - omit the dose that day
- If taken twice daily - omit both doses that day
How should DPP-4 inhibtiors (-gliptins) and GLP-1 analogues (-tides) be altered prior to surgery?
Keep taking as normal
When would UH be used as pharmacological VTE prophylaxis in hospital?
Patients with CKD
Stepwise VTE prophylaxis in hospital?
a
1) Medical patients deemed at risk of VTE are started on pharmacological VTE prophylaxis
- no contraindications
- VTE risk outweighs bleeding risk
2) High risk –> add anti-embolic stockings alongside the pharmacological methods.
When should COCP/HRT be stopped prior to surgery?
4 weeks
For certain surgical procedures pharmacological VTE prophylaxis is recommended for all patients to reduce the risk of a VTE developing post-surgery.
What 3 procedures require post-op VTE prophylaxis?
1) hip replacement
2) knee replacement
3) fragility fractures of the pelvis, hip and proximal femur
How should OD insulin dose be changed on the day BEFORE and the day OF surgery?
OD insulin dose should generally be reduced by 20%
(this only applies to OD long acting insulin)
VTE prophylaxis in patients who will undergo an elective hip replacement?
Both mechanical & pharmacological methods of VTE prophylaxis
e.g. dalteparin + TED stockings
When should LMWH be started after surgery as VTE prophylaxis?
6 hours after
Would you expect to see fasciculations prior to paralysis in use of depolarising or non-depolarising muscle relaxants?
Depolarising e.g. suxamethonium
Mechanism of suxamethonium?
It is a non-competitive (depolarising) muscle relaxant.
Works by inducing prolonged depolarisation of the skeletal muscle membrane (this clinically manifests as a few seconds of fasciculations before profound paralysis occurs).
What is the muscle relaxant of choice for rapid sequence induction for intubation?
Suxamethonium
