Anaesthetic Drugs Flashcards
Propofol
- drug type
- dose
- uses
IV induction agent
1.5-2.5mg/kg
Propofol pros and cons
Pros;
- suppresses airway reflexes well (prevents laryngospasm)
- low PONV
Cons:
- drop in HR/BP
- pain on injection
- involuntary movements
Thiopentone
- drug type
- dose
- uses
IV induction agent
4-5mg/kg
Quick acting, used for rapid-sequence induction
Thiopentone pros and cons
Pros;
- Protects brain by reducing O2 demand (anti-epileptic properties)
- rapid acting
Cons;
- hypotension
- apnoea
- myoclonus
- rash, bronchospasm
Ketamine
- drug type
- dose
- uses
IV induction agent
1-1.5mg/kg
Dissosicative anaesthesia, producing anterograde amnesia
Ketamine pros and cons
Pros
- amnesia = good for short procedures
- good if haemodynamically unstable as sympathetic stimulation causes rise in HR and BP
Cons
- slower onset (90 seconds)
- emergence phenomenon (hallucinations)
Etomidate
- drug type
- dose
- uses
IV induction agent
0./3mg/kg
Etomidate pros and cons
Pros:
- rapid onset
- keeps BP/HR stable
Cons
- pain on injection
- spontaneous movement
- PONV
- adreno-corticol suppression for 7 hours
MAC definition
1 MAC = concentration of vapour which prevents reaction to a standard surgical stimulus in 50% of subjects
100% amnesia
Lower the MAC = more potent agent
Isoflurane
Inhalation/maintenance anaesthetic
Least effect on organ blood flow, so used for organ transplants
Sevoflurane
Used for inhalation induction if IV access not possible (e.g. children)
Sweet smelling
Desflurane
Inhalation/maintenance anaesthetic
Used on longer operations as less accumulates in the fat.
Rapid onset and offset
Depolarising muscle relaxant MOA
Ach agonist
- bind to nicotinic receptors on post-synaptic cleft and cause muscle contraction
SLOWLY hydrolysed by acetylcholinesterase
- muscle contraction THEN fatigue and relaxation
Suxamethonium
- drug type
- dose
- use
Depolarising muscle relaxant
1-1.5mg/kg
Rapid sequence induction (rapid onset and offset)
- lasts 4-10 mins
Cons of suxamethonium
- muscle pain
- fasciculations
- hyperkalaemia (due to breakdown of muscle fibres)
MALIGNANT HYPERTHERMIA = fever, HTN, muscle spasm, acidosis and arrhythmias
SUZAMETHONIUM APNOEA = prolonged effects due to inability to break down drug
IRREVERSIBLE
Non-depolarising muscle relaxant MOA
pros and cons
Nicotinic receptor antagonist
- prevent Ach binding at post-synaptic cleft
- prevents muscle contraction
pros = less side effects
cons = slow onset, variable duration
Examples of non-depolarising muscle relaxant
- Short acting (15 mins) = mivacurium
- Medium acting (20-60 mins) = vecuronium, rocuronium, atracurium
- Long acting (60 mins) = pancuronium
Neostigmine + glycopyrolate
REVERSAL OF NON-DEPOLARIISNG MUSCLE RELAXANT
Neostigmine = anti-cholinesterase, so increases Ach at neuromuscular junction, returning muscle function
Glycopyrolate = anti-muscarinic to be given alongside to reverse muscarinic effects of Ach
Sugammadex
REVERSAL OF NON-DEPOLARISING MUSCLE RELAXANT
Reduced concentration of non-depolarising relaxant by forming water soluble complex with it.
Inotropes indications in anaesthesia
- MOA
- example
Hypotension
Increase HR and contractility, so increase BP
e.g. edhedrine
Local anaesthetic MOA
Inhibits voltage gated Na+ channels
Prevents propagation of action potential along nerve axon
Sensory information does not reach the brain
Esters
Local anaesthetics more likely to cause allergic reaction.
They are less stable and less commonly used
ONE i in name
- e.g. cocaine, procaine, benzocaine
Amides
Local anaesthetics more commonly used
TWO i’s in name
- e.g. bupivacaine, lignocaine
Local anaesthetic doses with/without adrenaline
- lignocaine
- bupivacaine
- prilocaine
WITHOUT:
- Lignocaine = 3mg/kg
- Bupivacaine = 2mg/kg
- Prilocaine = 6mg/kg
WITH:
- Lignocaine = 7mg/kg
- Bupivacaine = 2mg/kg (same)
- Prilocaine = 9mg/kg
Management of anaesthesia induced N+V
Prophylaxis = ondansetron
Peri-operative = dexamethasone
Post-operative = ensure one is prescribed during handover (e.g. cyclizine)
Stop COCP how long before anaesthetics
4 weeks + for 2 weeks after
Stop warfarin how long before anaesthetics
5 days
Replace with heparin for up to 4 hours before
stop DOACs how long before anaesthetics
24-48 hours
stop ACEi how long before anaesthetics
avoid on morning of
DO NOT NEED TO AVOID BB
Stop aspirin/clopidogrel how long before anaesthetics
7 days
Eating and drinking rules before anaesthetics
Food/milk containing drinks = 6 hours before
Breast milk = 4 hours before
Clear fluids = 2 hours before (1 hour for children)
Alcohol = 24 hours before
Advise to avoid boiled sweets/gum
