Magnesium-supplemented warm blood cardioplegia in patients undergoing coronary artery revascularization

Abstract

Background. Although there is growing evidence to suggest that the administration of magnesium (Mg 2+) to patients undergoing coronary artery bypass grafting (CABG) and to patients after myocardial infarction is beneficial, the addition of Mg 2+ to cardioplegic solutions remains controversial. The aim of this study was to compare the effects of intermittent warm blood cardioplegia with and without Mg 2+ supplementation on the early postoperative clinical outcomes in patients undergoing both elective or urgent CABG. Methods. Four hundred patients undergoing CABG were prospectively randomized to receive either blood cardioplegia without Mg 2+ (BC, n = 200) or supplemented with Mg 2+ (BC-Mg 2+, n = 200). Serial plasma Mg 2+ concentrations were recorded at base line and postoperatively from days 1 to 4. Results. Patient characteristics were similar and no significant differences were found in early mortality and morbidity in the two groups. Analysis of 178 patients undergoing urgent CABG for unstable symptoms (BC = 95, BC-Mg 2+ = 83) demonstrated a significantly lower requirement for internal defibrillation and temporary epicardial pacing in the BC-Mg 2+ group. Furthermore, there was a nearly twofold lower incidence of new postoperative atrial fibrillation in the BC-Mg 2+ group compared with the BC group (19% versus 34%, p = 0.03). Postoperative plasma Mg 2+ levels were consistently lower in those patients who developed new postoperative atrial fibrillation compared with those who did not ( p = 0.05). Conclusions. The addition of Mg 2+ to warm blood cardioplegia resulted in a lower incidence of intraoperative and postoperative arrhythmias in patients undergoing urgent CABG for unstable angina.