THE OPTIMAL CARDIOPLEGIC TEMPERATURE

Seventy-two patients undergoing coronary artery bypass grafting were r andomized to receive cold (8 degrees C) antegrade or retrograde, tepid (29 degrees C) antegrade or retrograde, or warm (37 degrees C) antegr ade or retrograde blood cardioplegia (n = 12 in each group). Myocardia l oxygen utilization as well as lactate and acid metabolism were asses sed intraoperatively and cardiac function was assessed postoperatively . Myocardial oxygen consumption and anaerobic lactate release were gre atest during warm, intermediate during tepid, and least during cold ca rdioplegic arrest. Myocardial oxygen consumption and lactate release w ere underestimated during retrograde cardioplegia because of contamina tion of aortic root samples. Warm retrograde and tepid retrograde card ioplegia resulted in greater lactate and acid washout with reperfusion . Left ventricular stroke work indices were greater after warm antegra de and tepid antegrade cardioplegia than after cold antegrade cardiopl egia, and right ventricular stroke work indices were greatest after wa rm antegrade cardioplegia. Warm antegrade cardioplegia increased aerob ic metabolism during and after cardioplegia and preserved left and rig ht ventricular function. Tepid antegrade cardioplegia reduced anaerobi c lactate and acid release during arrest and preserved cardiac functio n.