Rate-pressure product and arterial oxygen saturation during electroconvulsive therapy

The arterial oxygen saturation, heart rate and systolic blood pressure were measured in 100 patients undergoing electroconvulsive therapy under general anaesthesia. All patients were anaesthetised using thiopentone and suxamethonium. In spite of ventilation with oxygen during the procedure a marked degree of hypoxaemia occurred during the convulsion in 80% of the patients. This was associated with a highly significant rise in heart rate and blood pressure (p less than 0.001). During electroconvulsive therapy there is an imbalance between myocardial oxygen supply and consumption.