[Whole body oxygen uptake in coronary artery bypass surgery (author's transl)]

In 10 patients who underwent aorto-coronary bypass operations haemodynamic parameters and whole body oxygen uptake were monitored, beginning after induction of anaesthesia, during extracorporeal circulation and the postoperative period up to 5 h. In the intensive care unit a new device for the continuous measurement of whole body oxygen uptake from expired gases was used. For anaesthesia constant doses of fentanyl (10 micrograms/kg/h) and nitrous oxide were given. These were supplemented by low concentrations of halothane and nitroglycerine if hypertension occurred. Before extracorporeal circulation hypertensive states were observed in 8 cases and were effectively controlled without compromising tissue oxygenation. During extracorporeal circulation oxygen consumption was reduced more than could be explained only by the effects of hypothermia, indicating a limited shock state. Within the first postoperative hour the total peripheral resistance increased more than during the whole operation, impairing cardiac function at low levels of oxygen uptake. Thereafter a rise in metabolism was seen, partially induced by shivering which led to a marked (235% of control) increase in whole body oxygen uptake. This was accompanied by a reduction of the total peripheral resistance and an improvement of cardiac function. No acidosis was observed. Artificial ventilation is mandatory until metabolic demands have normalized. Noninvasive continuous monitoring of whole body oxygen uptake was useful for the assessment of cardiovascular function, increased postoperative metabolic demands, early detection of hypovolaemia and weaning from artificial ventilation.