Succinylcholine neuromuscular block in the myasthenia gravis patient.

The decrease of “functional” endplate receptors in MG can decrease the response to the chemical transmitter acetylcholine, as well as to the depolarizing muscle relaxant succinylcholine. In contrast, the decreased “safety margin” results in a marked sensitivity to nondepolarising relaxants. In normal patients, the wide “safety margin” may explain the slow onset of nondepolarizing block, as well as the rapid onset of succinylcholine depolarizing block. In myasthenic patients (Fig. 1), the decreased “safety margin” not only potentiates the neuromuscular block of non-depolarizing neuromuscular lockers, but also speeds its onset of action. In contrast, this can decrease the depolarizing action of succinylcholine, with a subsequent resistance and delayed onset of action4.