Objective of the study was to compare two commonly used anesthetic drugs, S-ketamine and etomidate, regarding their influence on seizure characteristics, safety aspects, and outcome of electroconvulsive therapy (ECT) in major depression. Treatment data of 60 patients who underwent a total number of 13 ECTs (median) because of the severe or treatment-resistant major depressive disorder (DSM-IV) were analyzed. Etomidate, mean dosage (SD) = 0.25 (0.04) mg/kg, was used for anesthesia in 29 participants; 31 patients received S-ketamine, mean dosage (SD) = 0.96 (0.26) mg/kg. Right unilateral brief pulse ECTs were performed. The number of ECTs was individually adjusted to clinical needs, mean (SD) = 13.0 (4.3). Seizure characteristics, adverse events, and the clinical global impression (CGI) scores were compared between the both groups during ECT series. In the S-ketamine group, a lower initial seizure threshold (p = 0.014), stimulation charge (p < 0.001), higher postictal suppression (p < 0.001), EEG ictal amplitude (p = 0.04), EEG coherence (p < 0.001) and maximum heart rate (p = 0.015) were measured. Etomidate was associated with more frequent abortive seizures (p = 0.02) and restimulations (p = 0.01). The CGI scores, the number of sessions within an ECT series, and the incidence of adverse events did not differ between groups. Due to its lower initial seizure threshold, S-ketamine might hold a potential to become a clinically favorable anesthetic agent during ECT. However, the current findings should be interpreted with caution, and further prospective randomized clinical trials are required. Also, specific adverse effects profile of S-ketamine, especially with regard to the cardiovascular risk, needs to be taken into account.
Keywords: ECT; Etomidate; Ketamine; Major depression; Narcosis; Seizure quality.