Write a short note on Complications of Suxamethonium.

Overview

Despite its usefulness, suxamethonium has a wide range of adverse effects, some serious, which explains the search for alternatives (e.g. Rocuronium) for rapid sequence induction.

Key Complications

• Hyperkalaemia — a normal rise of ~0.5 mmol/L, but dangerous, potentially fatal in burns, major trauma/crush, spinal cord injury, denervation and prolonged immobility (up-regulated extrajunctional receptors) — can cause cardiac arrest.
• Malignant hyperthermia trigger.
• Bradycardia/arrhythmias (especially repeat doses, children) — prevent with atropine.
• Muscle pains (myalgia) from fasciculations. Raised intra-ocular, intracranial and intragastric pressure.
• Suxamethonium apnoea (cholinesterase deficiency).
• Anaphylaxis (one of the commoner anaesthetic triggers). Prolonged/repeated dosing → phase II block.

Alternatives & Context

The sheer breadth of these complications is the reason that, wherever its unique rapid-on/rapid-off profile is not essential, suxamethonium is avoided in favour of a non-depolarising agent, and why rocuronium with sugammadex reversal has increasingly replaced it even for rapid sequence induction. Where suxamethonium is still used, susceptible patients are identified in advance — those with burns, crush or spinal injuries, denervating neuromuscular disease or a family history of malignant hyperthermia or of prolonged apnoea — and an alternative is chosen for them, atropine is available for bradycardia, and the patient is warned about postoperative myalgia.

Hyperkalaemic arrest in burns and denervation is the feared complication.

• Hyperkalaemia (fatal in burns/crush/spinal injury/denervation) → contraindicated there.
• Malignant hyperthermia trigger; bradycardia (atropine); myalgia.
• Raises IOP/ICP/intragastric pressure; suxamethonium apnoea; anaphylaxis.
• Large/repeated doses → phase II block.