Effects of halothane on coronary haemodynamics and myocardial metabolism in patients with ischaemic heart disease and heart failure.

Halothane was administered at an end-tidal concentration of 1% to 10 patients with stable ischaemic heart disease and clinical and haemodymanic signs of moderate heart failure. Measurements of central haemodynamic variables, coronary sinus blood flow and oxygen, lactate and hypoxanthine balances over the myocardium were done before and at steady state during halothane anaesthesia. Halothane induced marked haemodynamic changes with decreases in mean arterial pressure (-43%), mean pulmonary arteriolar occlusion pressure (-42%), systemic vascular resistance (-31%), cardiac index (-20%) stoke volume index (-31%) and left and right stroke work indices (-62% and -55%, respectively). Heart rate and pulmonary vascular resistance did not change. Coronary sinus blood flow decreased in parallel with perfusion pressure, and myocardial oxygen consumption decreased (-40%), as did myocardial oxygen extraction. Rate pressure product and triple product correlated better with changes in myocardial oxygen consumption in the present subset of patients than in healthy volunteers during halothane anaesthesia. The findings suggest that halothane, through its systemic vasodilatory effect, unloads the failing left ventricle and that this peripheral action predominates over the direct cardiodepressant action of the agent. The combined findings of unchanged coronary vascular resistance, decreased myocardial oxygen extraction and absence of increasing or pathological levels of lactate and hypoxanthine in coronary sinus blood imply a direct dilatory effect of halothane on the coronary vasculature.