Abstract 12438: Intraoperative Magnesium Reduces Postoperative Arrhythmias in Congenital Heart Surgery Is the Effect Arrhythmia-Specific and Dose-Dependent?

Abstract

Introduction: Magnesium (MG) has been used to decrease the incidence of postoperative junctional ectopic tachycardia (PO JET); its efficacy on other arrhythmias (A) is less known. We tested the hypotheses that the effect of MG on PO A may be: 1) arrhythmia-specific and 2) dose-dependent. Methods: 1871 out of a total of 2208 congenital heart surgeries (CHS), performed from 2005 to 2013, were reviewed based on selection criteria. 750 cases did not receive MG, 338 cases received 25 mg/kg MG (25 Mg) and 783 cases received 50 mg/kg MG (50 Mg) after aortic cross clamp release. All procedures were classified according to Aristotle Score (1 to 4). The incidence of 5 PO A categories was recorded: JET, accelerated junctional rhythm (AJR), atrial tachycardia (AT), ventricular tachycardia (VT) and 2°and 3° heart block (HB). Pearson chi-square test and logistic model analyses were used to evaluate the effect of MG on arrhythmia. BSA, Aristotle score, cardiopulmonary bypass, aortic cross-clamp and surgery times were controlled in logistic models. Results: 1) PO JET was reduced with MG use (0 Mg 15.3%; Mg 7.2%; p<0.001), but without evidence of a difference by dose (25 Mg 7.1%: 50 Mg 7.3%). 2) AJR was reduced with MG use (0 Mg 4.3%: 25 Mg 2.4%: 50 Mg 2.2%, NS between doses). 3) AT was reduced with MG use (0 Mg 9.1%: 25 Mg 3.6 %: 50 Mg 4.0%, NS between doses). 4) VT was reduced in low dose (0 Mg 5.1%: 25 Mg 2.7%; p =0.02), but not at the higher dose (50 Mg 5.5%). 5) PO HB did not differ by Mg use (0 Mg 4.8 %: 25 Mg 3.3 %: 50 Mg 2.6 %). The reduction of PO JET was significantly greater with increasing surgical complexity. Effect of MG was independent of Aristotle score in other A- categories. Conclusion: In agreement with prior clinical trial results, MG use was preventive of PO arrhythmia; however its effect appeared to be arrhythmia-specific. The occurrence of PO JET, AJR, and AT was reduced with Mg use. The effect of MG on PO VT appeared inversely dose dependent with no effect at higher dose and MG appeared to have no impact on PO HB. In general, higher doses of MG did not enhance PO arrhythmia suppression, but might be proarrhythmic (VT) in patients undergoing CHS. Our results suggest that an intraoperative MG dosage of 25 mg/kg may be optimal.