RESUMEN
BACKGROUND: Thiopental anesthesia increases the seizure threshold of patients receiving electroconvulsive therapy. However, excessive neuronal suppression could result in an unacceptably short seizure duration. We sought to identify the correlation between the pre-ictal Bispectral index (BIS) score and seizure duration during electroconvulsive therapy (ECT) under thiopental anesthesia. METHODS: Thirty patients with major depressive disorders underwent ECT. Anesthesia was induced by a bolus injection of 2 mg/kg of thiopental. BIS was monitored continuously, and recorded at specific end points, i.e., before anesthesia, just before ECT (pre-ictal BIS), on awaking (eye opening), before discharge to the recovery room and before discharge to the ward. The durations of motor and electroencephalographic seizures were recorded. RESULTS: The BIS score just before ECT was 52+/-9. Both motor and electro encephalographic seizure durations were positively correlated with the pre-ictal BIS score (R = 0.59 and 0.60, respectively; P < 0.01). On eye opening, BIS showed 48+/-13 and slowly recovered but remained low until discharge to the ward, reflecting post-ictal suppression. CONCLUSIONS: Pre-ictal BIS score is positively correlated with seizure duration, but the BIS score may not accurately reflect the depth of sedation after ECT.