Physiological response to ECT stimulus dose.

For a physiological effect to be useful to regulate the electrical stimulus dose used in electroconvulsive therapy (ECT), it must show sensitivity to the stimulus dose. In the analogy of using blood drug concentration to regulate drug dosage, this concentration must be sensitive to the dose. Accordingly, we examined the sensitivity of several physiological effects to ECT stimulus dose. Previously no substantial sensitivity of physiological effects was found when generally effective ECT methods were used. EEG post-ictal suppression, recruitment phase duration, wave form regularity and spike-and-wave frequencies, peak seizure heart rate (HR), and several types of seizure duration were measured with standard and higher dose stimuli given on separate days to 24 subjects. Left frontal to right temporal asymmetric bilateral stimulus placement was applied. Peak HR (P=0.007, t=2.7) and EEG recruitment phase duration (P=0.04, t=1.9) varied with stimulus dose, by 12 beats/min and 1.3 s, respectively. Only peak HR (P=0.02, t=2.2) varied with stimulus dose (by 6 beats/min) when subjects who showed only EEG seizure but no motor seizures were excluded. Subjects who maintained peak HR near their individual maximum values received fewer ECTs than other subjects (P=0.00003, t=5.20); this greater efficacy suggests that the peak HR reflects clinical efficacy as well as stimulus dose. In addition to EEG measurements, peak HR is a candidate to measure ECT seizure quality and provide feedback for stimulus dose regulation.