Seizure Thresholds in Elderly Patients Treated with Electroconvulsive Therapy for Major Depressive Disorder: A Review

Predictors of Seizure Threshold in Right Unilateral Ultrabrief Electroconvulsive Therapy: Role of Concomitant Medications and Anaesthesia Used

BACKGROUND

An individualized approach to maximize electroconvulsive therapy (ECT) efficacy and minimize cognitive side effects is to treat patients relative to their seizure threshold (ST). However, although Right Unilateral-Ultrabrief (0.3 ms) (RUL-UB) ECT is increasingly used in clinical settings as an effective form of ECT with minimal cognitive effects, there is sparse data regarding predictors of ST.

OBJECTIVE

To analyze the relationship between ST and clinical and demographic factors in a sample of patients treated with RUL-UB ECT.

METHODS

Clinical, demographic and ECT data from 179 patients in ECT research studies were examined. Seizure threshold was titrated at the first ECT session. ECT was performed with a Thymatron(®) or Mecta(®) device, with thiopentone (2.5-5 mg/kg) or propofol (1-2 mg/kg) anaesthesia. Medications taken at the time of ST titration were documented. The association between ST and candidate predictor variables was examined with regression analysis.

RESULTS

Multiple regression analyses showed that 34% of the variance in ST (P < 0.001) could be predicted. Older age (R(2) = 0.194, P < 0.001), propofol (vs thiopentone) (R(2) = 0.029, P ≤ 0.01) and higher anaesthetic dose (mg in propofol equivalents) (R(2) = 0.029, P < 0.05) were found to be predictors of higher initial ST. Treatment with lithium (R(2) = 0.043, P < 0.01) and study site (R(2) = 0.019, P < 0.05) significantly predicted lower initial ST.

CONCLUSIONS

Empirical titration is recommended for accurate determination of ST in patients receiving RUL-UB ECT. Novel findings of this study are that propofol anaesthesia resulted in higher ST than thiopentone and concomitant treatment with lithium treatment lowered ST.

Clinical predictors of seizure threshold in electroconvulsive therapy: a prospective study

At the start and during the course of electroconvulsive therapy (ECT), estimation of the seizure threshold (ST) is useful in weighing the expected effectiveness against the risks of side effects. Therefore, this study explores clinical factors predicting initial ST (IST) and levels of ST during the ECT course. This prospective observational study included patients aged ≥18 years receiving ECT without contraindications for dose titration. At the first and every sixth consecutive ECT session, ST level was measured. Using multivariate linear regression and multilevel models, predictors for IST and change in ST levels were examined. A total of 91 patients (mean age, 59.1 ± 15.0 years; 37 % male; 97 % diagnosis of depression) were included. In multivariable analysis, higher age (β = 0.24; P = 0.03) and bifrontotemporal (BL) electrode placement (β = 0.42; P < 0.001) were independent predictors for higher IST, explaining 49 % of its variation. Also, these two variables independently predicted higher ST levels at different time points during the course. Using multilevel models, absence of a previous ECT course(s) predicted a steeper rise in ST during the course (P = 0.03 for the interaction term time*previous ECT). The age-adjusted dose-titration method is somewhat crude, resulting in some measurement error. Concomitant medication use could have influenced ST levels. Increasing age and BL electrode placement predicted higher (I)ST, which should be taken into account when selecting ECT dosage. Previous ECT course(s) may avoid an increase in ST during the course of ECT.