Myocardial protection related to magnesium content of cold blood hyperkalemic cardioplegic solutions in CABG

The objective of this study was to investigate whether the addition of magnesium to a hyperkalemic cardioplegic solution containing 1.2-1.5 mmol/L ionized calcium improves myocardial protection. Twenty-seven coronary artery disease (CAD) patients underwent coronary artery bypass grafting (CABG) received hyperkalemic (20-22 mmol/L potassium) cardioplegic solutions containing 1.2-1.5 mmol/L ionized calcium and were randomized to one of the following groups: Group A (n = 9) received 3-4 mmol/L magnesium cool blood cardioplegia (4 degrees C), Group B (n = 9) received 8-10 mmol/L magnesium cold blood cardioplegia (4 degrees C). Group C (n = 9) received 16-18 mmol/L magnesium cold blood cardioplegia (4 degrees C). The effect of myocardium protection of the three kinds of cardioplegic solutions were evaluated by clinical outcome, cTnI and CK-MB mass. Serial venous blood samples were obtained before induction, after cardiopulmonary bypass (CPB), postoperative 6 h, 24 h, 72 h, and 6th day, respectively. The percentage of myocardial autoresusciation in group B (100%) was significantly higher than that in groups A (77.8%) and C (66.7%). One patient in group A and two patients in group C needed an interim pacemaker, but none in group B. The period of postoperative mechanical ventilation and ICU stay in group B was shorter than in the other two groups. The level of cTnI and CK-Mb mass increased from postoperative 6 h (p < .05), reached peak in 24 h-72 h, and recovered postoperative 6th day. As compared with groups A and C, the plasma concentrations of cTnI and CK-MB mass in group B were significantly lower at 6 h, 24 h, and 72 h (p < .01). 8 approximately 10 mmol/L magnesium cold blood cardioplegia provides better myocardium protection than higher or lower concentrations.