[Continuous measurement of myocardial oxygen saturation using near-infrared spectroscopy during warm blood cardioplegia].

Continuous infusion of warm blood cardioplegic solution is often interrupted during coronary artery bypass grafting to obtain a bloodless operating field. We measured myocardial oxygen saturation continuously using near-infrared spectroscopy to determine myocardial oxygen metabolism during intermittent warm blood cardioplegia (IWBC). In 7 adult mongrel dogs undergoing cardiopulmonary bypass IWBC was administered using the Buckberg-Shiley system. Cardiac arrest was induced by a warm blood cardioplegic infusion of 100 ml/min for 5 minutes followed by a maintenance infusion of 40 ml/min for 5 minutes. The infusion of warm blood cardioplegia was then stopped for 15 minutes. Measurement of myocardial oxygen saturation was performed continuously throughout cardiopulmonary bypass. IWBC produced an increase in myocardial oxygen saturation for the first 5 minutes and a slight decrease for the second 5 minutes. After the termination of IWBC, myocardial oxygen saturation showed a marked reduction for 3 minutes and plateaued after 5 minutes. Measurement of myocardial oxygen saturation revealed myocardial oxygen metabolism during IWBC. This procedure may be a useful way to monitor myocardial oxygen metabolism during open heart surgery.