Low dose mivacurium is less effective than succinylcholine in electroconvulsive therapy

Purpose: To compare the efficacy of low dose (LD) mivacurium (0.08 mg.kg(-1 )) with LD succinylchoiine (0.5 mg.kg(-1)) in modifying seizure activity du ring electroconvulsive therapy (ECT). Partial muscle relaxation is used in ECT to prevent violent muscle contractions. Current practice is to use LD s uccinylcholine which has several undesirable side effects. Method: Sixteen depressed, but otherwise healthy, patients, aged 27-67 yr w ere studied; In a randomized, double-blind, cross-over study either LD miva curium or LD succinylcholine was given at consecutive ECTs 120 and 30 sec r espectively before inducing ECT. Neuromuscular blockade following mivacuriu m was not reversed. Seizure modification was scored - 0 = no seizure activi ty, 1 = over-modified, 2 = desired level, 3 = under-modified, 4 = unmodifie d. Duration of seizures, time to first breath and adequate ventilation, abi lity to protrude tongue and sustain hand grip for five seconds were recorde d. Paired t- tests and Wilcoxon matched pairs test were used to compare dat a. P < 0.05 was considered significant, Results: Seizure modification was better (mean (range)) after succinylchoii ne 2.06(1-3) than after mivacurium 2.56(2-4) (P < 0.05). Mivacurium was uns atisfactory in eight cases compared with two cases after succinylcholine. T he study was terminated early because of unsatisfactory seizure control. Cl inical assessments of recovery from both relaxants were similar. Conclusion: Low dose mivacurium is unsuitable for use in ECT.