Intermittent antegrade hyperkalaemic warm blood cardioplegia supplemented with magnesium prevents myocardial substrate derangement in patients undergoing coronary artery bypass surgery

Objective: The influence of the addition of magnesium on myocardial protect ion with intermittent antegrade warm blood hyperkalaemic cardioplegia in pa tients undergoing coronary artery surgery was investigated and compared wit h intermittent antegrade warm blood hyperkalaemic cardioplegia only. Method s: Twenty-three patients undergoing primary elective coronary revasculariza tion were randomized to one of two different techniques of myocardial prote ction. In the first group, myocardial protection was induced using intermit tent antegrade warm blood hyperkalaemic cardioplegia. In the second group, the same technique was used except that magnesium was added to the cardiopl egia. Intracellular substrates (ATP, lactate and amino acids) were measured in left ventricular biopsies collected 5 min after institution of cardiopu lmonary bypass, after 30 min of ischaemic arrest and 20 min after reperfusi on. Results: There were no significant changes in the intracellular concent ration of ATP or free amino acid pool in biopsies taken at the end of the p eriod of myocardial ischaemia. However, the addition of magnesium prevented the significant increase in the intracellular concentration of lactate see n with intermittent antegrade warm blood hyperkalaemic cardioplegia. Upon r eperfusion there was a significant fall in ATP and amino acid concentration when the technique of intermittent antegrade warm blood hyperkalaemic card ioplegia was used but not when magnesium was added to the cardioplegia. Con clusions: This work shows that intermittent antegrade warm blood hyperkalae mic cardioplegia supplemented with magnesium prevents substrate derangement early after reperfusion. (C) 1998 Elsevier Science B.V. All rights reserve d.