Extreme variability in succinylcholine dose for muscle relaxation in electroconvulsive therapy

To determine what dose of succinylcholine falls outside the range of 2 SD above or below the mean optimal dose of 0.9 mg/kg used for electroconvulsive therapy (ECT).

In this retrospective chart review, for all patients who received ECT at our institution within the 5-year study period, the initial dose of succinylcholine in milligrams per kilogram was compared with subsequent doses after adjustments were made for individual patient responses. Mean and SD were calculated using the dose of succinylcholine, once the optimal dose for each patient had been determined, based on clinical response.

Five hundred patients treated during the 5-year period met inclusion criteria, 180 (36%) of whom required an adjustment of the succinylcholine dosing either above (119 patients) or below (61 patients) the 0.9 mg/kg standard after their first treatment.

In those patients who required an adjustment of 2 SD either above or below the mean dose of succinylcholine (29 patients, 5.8%), adequate neuromuscular blockade was only achieved with either an increased dose of up to 2.10 mg/kg or a decreased dose as low as 0.29 mg/kg.