Muscle Relaxants and Reversal Agents Flashcards
What doesn’t muscle relaxation ensure?
Unconsciousness
Amnesia
Analgesia
Why are muscle relaxants used?
Make surgical field easier
Make airway management easier
What is Lambert-Eaton myasthenic syndrome?
Autoimmune disorder
AutoAbs to receptors on presynaptic membrane at neuromuscular junction (NMJ)
Characterised by limb weakness
What is myasthenia gravis?
Autoimmune disorder
AutoAbs to ACh receptors on post-synaptic membrane at NMJ
What are two classes of neuromuscular blocking agents?
Depolarising
Non-depolarising
What is the mechanism of action of depolarising neuromuscular blocking agents?
Very closely resemble ACh
Readily bind to AChRs > depolarise motor end plate
= ACh agonists
What phase block are depolarising neuromuscular blocking agents?
Phase I
What is the mechanism of action of non-depolarising neuromuscular blocking agents?
Bind ACh > don’t let motor end plate depolarise > no action potential
= ACh competitive antagonists
What is the reaction to the different classes of neuromuscular blocking agents in conditions associated with chronic release of ACh?
More sensitive to depolarising agents
Less sensitive to non-depolarising agents
What is the reaction to the different classes of neuromuscular blocking agents in conditions associated with chronically low levels of ACh?
Less sensitive to depolarising agents
More sensitive to non-depolarising agents
What are the pharmacokinetics of succinylcholine?
Short-acting
Short half-life
What is the adult dose for succinylcholine for intubation?
1-1.5 mg/kg, IV
Repeated small boluses/infusion can be used where short but intense paralysis needed for surgical procedure
What are the side effects of succinylcholine?
Relatively safe Risk of - Hyperkalaemia - Rhabdomyolysis - Cardiac arrest in children with undiagnosed myopathies Stimulates all ACh receptor - Bradycardia - SLUDGE syndrome Malignant hyperthermia Apnoea
What is SLUDGE syndrome?
Acronym for symptoms due to activation of ACh receptors, thus activating PNS S = salivation L = lacrimation U = urination D = diarrhoea G = gastrointestinal stress E = emesis
What is the drug class of rocuronium?
Non-depolarising neuromuscular blocking agent
When is rocuronium used?
If can’t use succinylcholine
What is the duration of rocuronium in comparison to succinylcholine?
Much longer duration of action
What is the metabolism of rocuronium, and thus, what are the implications?
Eliminated primarily by liver > safe in renal failure, but not liver failure
What is the drug class of atracurium?
Non-depolarising neuromuscular blocking agent
What are the side effects of atracurium?
Triggers histamine release - Significant at doses >0.5 mg/kg Hypotension and tachycardia - Usually if dose >0.5 mg/kg Bronchospasm - Avoid in asthmatic patients
What is the drug class of cisatracurium?
Non-depolarising neuromuscular blocking agent
What is the dose for cisatracurium?
0.1-0.15 mg/kg
What is the effect of cisatracurium on histamine release?
No effect
What is the drug class of pancuronium?
Non-depolarising neuromuscular blocking agents
What are the side effects of pancuronium?
HTN and tachycardia
Arrhythmias
Allergic reactions possible if hyper-sensitive to bromides
How is rocuronium reversed?
ACh esterase inhibitor = sugammadex
What is the mechanism of action of sugammadex?
Block esterase > buildup of ACh > displaces drug
What are the side effects of sugammadex?
Bradycardia
SLUDGE syndrome
What is given to prevent SLUDGE syndrome?
Atropine
Glycopyrate
