Optimization of coronary perfusion rate during cardiac surgery in man.

Myocardial oxygen consumption (Vo2) and lactate flux were measured in 12 patients with aortic valve disease and left ventricular hypertrophy during cardiac surgery with hypothermic cardiopulmonary bypass and artificial coronary perfusion. Coronary flow was varied from "standard" flow-defined as giving a "line pressure" of 110 mm. Hg-to 25 or 50 percent higher than standard flow. Lactate flux was not significant at any flow. Vo2 was higher at +25 percent flow that at standard flow, but no significant further increase in Vo2 occurred at +50 percent. Myocardial Q10 and coronary vascular resistance also approached optimal values at a flow of +25 percent, corresponding with a mean coronary flow of 203 ml. times min -1. The difficulties are discussed of standardizing coronary perfusion in useful practical terms.