Muscle relaxants & reversal
also: suxamethonium · rocuronium · atracurium · neostigmine · sugammadex
Overview
Paralysis for intubation and surgery, and the agents that reverse it. Suxamethonium's adverse effects are a heavy exam favourite.
Mechanism
Depolarising blocker (suxamethonium) is an ACh-receptor AGONIST → sustained depolarisation → initial fasciculation then flaccid paralysis; fast on/off. Non-depolarising blockers ("-curium/-ronium") are competitive ACh-receptor ANTAGONISTS. Reversal: neostigmine (anticholinesterase, raises ACh) for non-depolarising; sugammadex directly encapsulates rocuronium/vecuronium.
Indications
- Tracheal intubation (esp. rapid sequence induction)
- Intra-operative muscle relaxation
The agents
ultra-short
RSI. AEs: hyperkalaemia, malignant hyperthermia, bradycardia, sux apnoea (pseudocholinesterase deficiency), myalgia.
Atracurium: Hofmann elimination (good in renal/hepatic failure), histamine release.
with glycopyrronium
Reverses non-depolarising; give antimuscarinic to block bradycardia.
Rapid reversal of rocuronium/vecuronium.
Adverse effects
Prolonged paralysis in pseudocholinesterase deficiency — ventilate until it wears off.
Dangerous in burns, crush injury, denervation.
Cautions & contraindications
Life-threatening K⁺ rise.
Interactions
- Aminoglycosides potentiate neuromuscular block
Monitoring & kinetics
Train-of-four nerve stimulation; ensure full reversal before extubation
IV. Sux ultra-short; non-depolarisers intermediate/long.
Source: BNF — Neuromuscular blocking drugs