Magnesium supplementation in the prevention of arrhythmias in pediatric patients undergoing surgery for congenital heart defects

Background The efficacy of magnesium in the prevention of arrhythmias in pe diatric patients after heart surgery remains unknown. Therefore we prospect ively examined the effect of magnesium treatment on the incidence of postop erative arrhythmias in pediatric patients undergoing surgical repair of con genital heart defects. Methods and Results Twenty-eight pediatric patients undergoing heart surger y with cardiopulmonary bypass were prospectively, randomly assigned in a do uble-blind fashion to receive intravenous magnesium (magnesium group, n = 1 3; 30 mg/kg) or saline (placebo group, n = 15) immediately after cessation of cardiopulmonary bypass. Magnesium, potassium, and calcium levels were me asured at defined intervals during surgery and 24 hours after surgery. Cont inuous electrocardiographic documentation by Holter monitor was performed f or 24 hours after surgery. Magnesium levels were significantly decreased be low the normal reference range for patients in the placebo group compared w ith the magnesium group on arrival in the intensive care unit and for 20 ho urs after surgery. Magnesium levels remained in the normal range for patien ts in the magnesium group after magnesium supplementation. In 4 patients in the placebo group (27%), junctional ectopic tachycardia developed within t he initial 20 hours in the intensive care unit. No junctional ectopic tachy cardia was observed in the magnesium group (P = .026). Conclusions Although this study was originally targeted to include 100 pati ents, the protocol was terminated because of the unacceptable incidence of hemodynamically significant junctional ectopic tachycardia that was present in the placebo group. Thus low magnesium levels in pediatric patients unde rgoing heart surgery are associated with an increased incidence of junction al ectopic tachycardia in the immediate postoperative period.