TEPID ANTEGRADE AND RETROGRADE CARDIOPLEGIA

To determine the optimal temperature for the combination of antegrade and retrograde cardioplegia, 42 patients undergoing coronary artery bypass grafting were randomized to receive cold (9 degrees C; n = 14), tepid (29 degrees C; n 14), or warm (37 degrees C; n = 14) blood cardioplegia delivered continuously retrograde and intermittently antegrade. Myocardial oxygen utilization, lactate and acid metabolism, and coronary vascular resistance were measured during the operation and cardiac function was assessed postoperatively. Myocardial oxygen consumption, lactate release and acid release were greatest with warm, intermediate with tepid, and least with cold cardioplegia (p = 0.0001). However, washout of lactate and acid at the time of cross-clamp release was reduced (p = 0.022) with tepid or cold compared with warm cardioplegia. Early postoperative left ventricular function was best preserved (p 0.01) after tepid than after cold or warm combination cardioplegia. These results suggest that tepid combination cardioplegia reduced metabolic demands but permitted immediate recovery of cardiac function. This technique may provide better myocardial protection than cold or warm combination cardioplegia.