A pre-induction test dose for suxamethonium.

A two-part experimental and clinical study was conducted to determine the effects of administration of a pre-induction dose of suxamethonium, and to see whether the symptoms produced could form the basis of a test dose, to determine sensitivity to suxamethonium prior to administration of a full intubation dose. Suxamethonium was shown to produce distinctive clinical features characterised by signs of both extraocular muscle contraction and paresis, manifest by symptoms of eye and eyelid heaviness without generalised paresis. The dose response was determined in individuals with normal plasma cholinesterase, to a test dose of suxamethonium chloride of between 20 and 1 micrograms/kg. Individuals with abnormal plasma cholinesterase were shown to exhibit sensitivity to these low doses and were easily distinguished from those with normal enzyme. A protocol is suggested which can conveniently establish, prior to induction, those individuals with a reduced ability to hydrolyse suxamethonium.