Myocardial potassium and lactate balance during valve-replacement surgery.

Abstract

Coronary venous drainage was isolated, and arterial and coronary venous lactate and potassium concentrations were determined during valve-replacement surgery in 15 patients. Coronary flow was measured in seven. Fourteen had diminished lactate uptake during control periods of normothermic bypass whereas potassium uptake or loss was variable. The recovery period after intermittent anoxic cardiac arrest for 10 to 20 minutes at 28° C (five patients) and 4° C (seven patients) was associated with lactate production and large potassium losses. Continuous coronary perfusion at 28° C and 150 to 250 ml/min flow (three patients) was associated with continuous lactate production and potassium loss. Total myocardial potassium loss averaged 1.15 mEq. In most patients lactate production diminished and rapid potassium uptake occurred when normal coronary perfusion was reestablished while still on bypass. In spite of these shifts in potassium balance, myocardial function was regained promptly upon defibrillation without serious arrhythmias.