Magnesium supplementation during cardiopulmonary bypass to prevent junctional ectopic tachycardia after pediatric...

We analyzed the role of magnesium sulfate (MgSO(4)) supplementation during cardiopulmonary bypass in pediatric patients undergoing cardiac surgery, assessing the incidence of hypomagnesemia and the incidence of junctional ectopic tachycardia.

We performed a randomized, double-blind, controlled trial in 99 children. MgSO(4) or placebo was administered during the rewarming phase of cardiopulmonary bypass: group 1, placebo group (29 patients); group 2, 25 mg/kg of MgSO(4) (30 patients); and group 3, 50 mg/kg of MgSO(4) (40 patients).

At the time of admission to the cardiac intensive care unit, groups receiving MgSO(4) had significantly greater levels of ionized magnesium (group 1, 0.51 + or - 0.07; group 2, 0.57 + or - 0.09; group 3, 0.59 + or - 0.09). Hypomagnesemia before bypass was common (75%-86.2%) and not significantly different among the groups. The proportion of hypomagnesemia decreased significantly at admission to the cardiac intensive care unit in groups receiving MgSO(4) (group 1, 77.8%; group 2, 63%; group 3, 47.4%). Patients receiving placebo (group 1) had a significantly greater occurrence of junctional ectopic tachycardia than groups receiving MgSO(4) (group 1, n = 5 [17.9%]; group 2, n = 2 [6.7%]; group 3, n = 0 [0%]). Age (<1 month), Aristotle score (>4), and history of cardiac failure were associated with junctional ectopic tachycardia. None of the patients with those characteristics in group 3 had junctional ectopic tachycardia. No association was found between study groups and the Pediatric Risk of Mortality score or length of stay in the cardiac intensive care unit.

Supplementation with MgSO(4) during cardiopulmonary bypass seems to reduce the incidence of hypomagnesemia and junctional ectopic tachycardia at admission to the cardiac intensive care unit. This effect seems to be dose related.