Interrupted warm blood cardioplegia for coronary artery bypass grafting

Continuous warm blood cardioplegia has been used with good clinicaloutcome in both antegrade and retrograde delivery. However, the continuousdelivery of cardioplegia is sometimes interrupted for adequatevisualization and flow is not constant with heart manipulation duringoperation. We studied the effects of interrupted antegrade delivery of warmblood cardioplegia on myocardial metabolism and clinical results aftersurgery. Fifty-five patients undergoing isolated coronary bypass surgeryreceived warm blood cardioplegia (n = 29) or cold crystalloid cardioplegia(n = 26) in an antegrade fashion. During reperfusion, myocardial oxygenconsumption, lactate extraction, creatinine kinase isoenzyme (CK-MB), andmalondialdehyde (MDA) were measured. Post-operatively, serum CK-MB andcardiac output (CO) were determined over a period of time. Myocardialoxygen extraction in the warm group was significantly greater than in thecold group 1 min after reperfusion (P ≪ 0.02). The results revealed atendency for patients in the warm group to have prior lactate extraction,although the difference did not reach statistic difference (P ≪ 0.10).After removal of the aortic cross-clamp, the heart returned to sinus rhythmspontaneously in 90% of the patients with warm cardioplegia and 15.4% ofthose with a cold heart (P ≪ 0.01). Postoperatively, there was nosignificant CK-MB or MDA release in either group except for one patientwith perioperative myocardial infarction. After operation inotropic supportwas required for two and one patient in the warm and cold groups,respectively, although there were significantly more patients with poorleft ventricular function in the warm, than in the cold, group (P ≪0.05).