Arrhythmia prophylaxis after coronary artery bypass grafting: regimens of magnesium sulfate administration

BACKGROUND: Arrhythmias are common after open heart surgery and may be related to hypomagnesaemia due to cardiopulmonary bypass. Although perioperative prophylactic Mg2+ administration may prevent arrhythmias after coronary artery bypass grafting (CABG), clear indications as well as the timing of Mg2+ substitution and dose regimen need to be clarified. Aim of this study was to evaluate the antiarrhythmic effects of Mg2+ infusion in patients who underwent elective CABG. METHOD: Ninety-seven patients who underwent elective CABG were divided in four Groups. In Group A 1 g of magnesium sulfate was added to the pump prime, Group B received 1 g in the pump prime plus 5 mmol/L in the cardioplegic solution, Group C received 5 mmol/L in the cardioplegic solution, and Group D was a placebo control Group. Groups A, B, and C also received 24 h continuous infusion of magnesium sulfate at 10 mmol/L. Three-channel electrocardiogram (II-V5-V6) continuous monitoring was performed 12 hours preoperatively and 48 hours postoperatively. Blood samples were taken for subsequent Serum magnesium measurements, at five different time points before, during and after CBP. RESULTS: In all Groups serum Mg2+ levels were reduced during CPB (Time 2) and statistically significant differences from pre-anaesthesia levels (Time 1) were noted (p <0.05). In Groups A, B, and C Serum Mg2+ levels increased progressively from Time 3 to Time 5; in Group D serum Mg2+ levels were still much lower at Time 5. Significant differences (p<0.05) were noted for Groups B and C vs Groups A and D in atrial ectopics, atrial fibrillation, and ventricular arrhythmic events. CONCLUSION: Our results demonstrate that Mg2+ sulfate administration regimens used in Group B and C reduce postoperative arrhythmic events in patients undergoing CABG.