MAGNESIUM SUBSTITUTION IN ELECTIVE CORONARY-ARTERY SURGERY - A DOUBLE-BLIND CLINICAL-STUDY

Magnesium may be beneficial in the control of ventricular ectopy and s upraventricular tachyarrhythmias after coronary artery bypass graft (C ABG) surgery, but it is not known whether a high-dose magnesium regime n is superior to a regimen keeping the patient normomagnesemic. A pros pective randomized and double-blind clinical comparison was performed in 81 elective CABG patients in order to assess the effects of two dif ferent magnesium infusion regimens on electrolyte balance and postoper ative arrhythmias. Forty-one patients (high-dose group, H) received 4. 2 +/- 0.7 g (mean +/- SD), of magnesium sulfate before cardiopulmonary bypass, followed by an infusion of 11.9 +/- 2.8 g of magnesium chlori de until the first postoperative (PO) morning, and a further 5.5 +/- 1 .0 g until the second PO morning. Forty patients (low-dose group, L) r eceived magnesium sulfate only after bypass to a total of 2.9 +/- 0.5 g at the first, and 1.4 +/- 0.1 g at the second PO morning. A blood ca rdioplegia technique was used in both groups, including bolus doses of magnesium chloride to a total of 2.4 +/- 0.6 g and 2.3 +/- 0.6 g to H and L patients, respectively. Continuous Hotter tape-recording was us ed for 12 to 15 hours preoperatively, and for 48 hours postoperatively . Serum magnesium peaked in H patients on the first PO morning at 1.60 a 0.25 mmol/L, whereafter it declined to the normal level on the thir d PO morning. Patients in the L group were normomagnesemic, except aft er the start of bypass. Recovery to spontaneous rhythm after declampin g of the aorta was better in the H patients; only one patient had vent ricular fibrillation (VF), whereas in the L group, four patients had V F and five patients needed a temporary pacemaker(p = 0.016). Atrial fi brillation (AF) was detected in 3 H (7.3%), and 10 L patients (25%) wi thin the first 48 PO hours (p = 0.037). Ten H (24.3%) and 18 L patient s (45.0%) had a total of 19 and 41 episodes of AF during the first PO week (p < 0.01). Paired ventricular ectopic beats were detected during the first 24 PO hours in 17 H (42.5%) and 27 L patients (71.1%) (p = 0.013). Copyright (C) 1995 by W.B. Saunders Company