Modification of tonic-clonic convulsions by atracurium in multiple-monitored electroconvulsive therapy

Study Objective: To determine the effect of two different doses of atracurium on the modification of tonic-clonic convulsions in multiple-monitored electroconvulsive therapy (MMECT). To compare recovery time and adverse reactions of these doses. Design: Clinical study. Anesthesiologist was blinded in the evaluation of post-electroconvulsive therapy (ECT) myalgia and other side effects. Setting: University-affiliated veterans general hospital. Patients: Two groups of twelve psychiatric inpatients who suffered from major depression or catatonic-type schizophrenia that failed to respond to tricyclic antidepressant therapy. Interventions: Under single-channel, prefrontal electroencephalographic (EEG) monitoring, patients were given either 0.3 mg/kg or 0.5 mg/kg of atracurium intravenously (IV) after anesthetic induction with methohexital 1 mg/kg IV. Measurements and Main Results: Evoked electromyographic responses of the adductor pollicis muscle was obtained by train-of-four stimulation of the ulnar nerve at the wrist every 20 seconds. The first twitch depression (T₁) of neuromuscular blockade was maintained within 11% to 25% (atracurium 0.3 mg/kg) or 0% to 10% (atracurium 0.5 mg/kg) of control during the entire session of MMECT. Patients pretreated with atracurium 0.5 mg/kg had significantly fewer ECT-induced moderate and vigorous convulsions when compared with patients receiving atracurium 0.3 mg/kg (16.7% vs. 78.4%, moderate; 0% vs. 8.3%, vigorous). However, patients pretreated with atracurium 0.5 mg/kg took a longer time to attain a T₄ ratio of 0.5 than did patients receiving atracurium 0.3 mg/kg (9.2 ± 0.8 minutes vs. 4.3 ± 0.4 minutes). There was no significant difference between the two groups with respect to cumulative seizure duration or frequency of bradycardia, sialorrhea, postseizure myalgia, nausea, headache, or confusion. No patient in either group recalled any event concerning electroconvulsive shock. Conclusions: Whereas full neuromuscular blockade by atracurium 0.5 mg/kg IV is very effective in the modification of tonic-clonic convulsions induced by ECT, we suggest that a lower dose of atracurium (0.3 mg/kg IV) be used if one needs to ascertain the occurrence of ECT-induced seizures as indicated by minimum peripheral muscle activity at the time of EEG recording during MMECT.