• Massimo Caputo, Kirkpatrick C Santo, Gianni D Angelini, Carlo Fino, Marco Agostini, Claudio Grossi, M-Saadeh Suleiman, and Barnaby C Reeves.
• Bristol Heart Institute, University of Bristol, Bristol Royal Infirmary, Bristol, BS2 8HW, UK.
• Eur J Cardiothorac Surg. 2011 Sep 1; 40 (3): 722-9.

ObjectiveMagnesium (Mg²⁺) is cardioprotective and has been routinely used to supplement cardioplegic solutions during coronary artery bypass graft (CABG) surgery. However, there is no consensus about the Mg²⁺ concentration that should be used. The aim of this study was to compare the effects of intermittent antegrade warm-blood cardioplegia supplemented with either low- or high-concentration Mg²⁺.MethodsThis study was a randomised controlled trial carried out in two cardiac surgery centres, Bristol, UK and Cuneo, Italy. Patients undergoing isolated CABG with cardiopulmonary bypass were eligible. Patients were randomised to receive warm-blood cardioplegia supplemented with 5 or 16 mmol l⁻¹ Mg². The primary outcome was postoperative atrial fibrillation. Secondary outcomes were serum biochemical markers (troponin I, Mg²⁺, potassium, lactate and creatinine) and time-to-plegia arrest. Intra-operative and postoperative clinical outcomes were also recorded.ResultsData from two centres for 691 patients (342 low and 349 high Mg²⁺) were analysed. Baseline characteristics were similar for both groups. There was no significant difference in the frequency of postoperative atrial fibrillation in the high (32.8%) and low (32.0%) groups (risk ratio 1.03, 95% confidence interval, CI, 0.82-1.28). However, compared with the low group, troponin I release was 28% less (95% CI 55-94%, p=0.02) in the high-Mg²⁺ group. The 30-day mortality was 0.72% (n = 5); all deaths occurred in the high-Mg²⁺ group but there was no significant difference between the groups (p=0.06). Frequencies of other major complications were similar in the two groups.ConclusionsWarm-blood cardioplegia supplemented with 16 mmol l⁻¹ Mg²⁺, compared with 5 mmol l⁻¹ Mg²⁺, does not reduce the frequency of postoperative atrial fibrillation in patients undergoing CABG but may reduce cardiac injury. (This trial was registered as ISRCTN95530505.).Copyright © 2011 European Association for Cardio-Thoracic Surgery. Published by Elsevier B.V. All rights reserved.

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