Seizure threshold in ECT: II. Dose titration vs age and half age methods.

Seizure threshold determination is of crucial importance in optimizing electrical stimulus dosage at electroconvulsive therapy (ECT). We measured initial seizure threshold by means of Srinakharinwirot University titration schedule in 106 patients with schizophrenia or schizoaffective disorder, receiving bilateral ECT. Seizure threshold was approximately 106 millicoulombs on average, and varied 5-fold across patients. Seizure threshold was directly related to age, but inversely related to motor seizure duration. Comparisons of stimulus charge were done with the Age and Half age methods. By using the Half age method, 68 per cent of patients would have seized at the first stimulation and resulted in a closer mean charge to dose-titration method than the Age method. The results may have important clinical implications for stimulus dosing strategy in ECT.