Myocardial Protection Related to Magnesium Content of Cold Blood Hyperkalemic Cardioplegic Solutions in CABG

Department of Cardiopulmonary Bypass, Cardiovascular Institute and FuWai Hospital, CAMS and PUMC, Beijing 100037, People’s Republic of China

^* Address correspondence to: Bingyang Ji, Department of Cardiopulmonary Bypass, Cardiovascular Institute and Fu Wai Hospital, CAMS and PUMC, Beijing, 100037, People’s Republic of China. E-mail: bingyangj@hotmail.com

Received: 25 March 2001
Accepted: 14 September 2001

Abstract

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°C), Group B (n = 9) received 8∼10 mmol/L magnesium cold blood cardioplegia (4°C). Group C (n = 9) received 16∼18 mmol/L magnesium cold blood cardioplegia (4°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∼10 mmol/L magnesium cold blood cardioplegia provides better myocardium protection than higher or lower concentrations.