Bilateral bispectral index monitoring during and after electroconvulsive therapy compared with magnetic seizure therapy for treatment-resistant depression

Background Electroconvulsive therapy (ECT) is a highly effective and established treatment for depression. Magnetic seizure therapy (MST) has recently been developed and seems equally effective while associated with fewer side-effects. Both require general anaesthesia, which could be quantified using the bispectral index (BIS). We compared ECT and MST with respect to recovery times, left-sided BIS, and left-right differences in BIS. Methods In this prospective, observational study, we enrolled 10 successive patients receiving ECT and 10 patients undergoing MST. Anaesthesia was performed with propofol and monitored with a bilateral BIS sensor. The seizure was elicited when the BIS was within a range from 50 to 60. The time to eye opening was measured and bilateral BIS were recorded for 10 min after seizure induction. Results A comparable anaesthetic depth was observed in the ECT and MST groups at baseline [mean (standard deviation, sd) BIS values of 94.1 (4.1) and 95.5 (3.0), respectively] and before seizure induction [mean (sd) BIS values of 52.3 (9.6) and 55.2 (10.3), respectively]. Post-ictally, MST patients opened their eyes significantly earlier than ECT patients [3.0 (1.0) vs 6.7 (1.3) min, P<0.001]. They showed a significantly higher BIS at 2 min after seizure induction [69.2 (10.1) vs 50.9 (15.9), P=0.003], and this difference was still present at 10 min after seizure induction [BIS 81.5 (6.5) vs 68.0 (16.4), P<0.001]. Significant differences between the left and right BIS were observed in neither the ECT nor the MST group. Conclusions At a comparable anaesthetic depth, MST is superior to ECT in terms of post-ictal recovery, which is correctly reflected by higher post-ictal BIS values. Unilateral BIS monitoring is sufficient to monitor anaesthetic depth in ECT and MST patients.