Background: del Nido cardioplegia (dNC) solution is widely used in pediatric and congenital cardiac surgery. In 2014, Cincinnati Children’s Hospital Medical Center (CCHMC) changed from Mee cardioplegic solution to dNC. Since Mee solution does not contain magnesium, magnesium was administrated post cross-clamp removal, at a dose of 25 mg/kg up to 1 g, to abate hypomagnesemia. This practice remained in place with the use of dNC. We postulated that patients may experience hypermagnesemia under this protocol. 

Methods: To determine if exogenous magnesium is necessary post-clamp removal in our practice, a study examining serum magnesium levels during cardiopulmonary bypass (CPB) was completed from January 2022 through October 2023 (IRB #2021-0816). One hundred patients undergoing CPB with cross-clamp, ranging from infants to adults, were consented. Two magnesium samples were collected. Draw 1 (D1) was collected post cardioplegia administration and 30 min prior to cross-clamp removal. Draw 2 (D2) was collected post-cross-clamp removal and 10 ± 2 min following magnesium administration. 

Results: Both samples demonstrated magnesium levels > 1.6 mg/dL or higher (normal magnesium range at CCHMC, 1.6–2.6 mg/dL). A Wilcoxon rank sum test demonstrated statistical significance for D1, comparing the number of samples that fell above 2.6 mg/dL vs. those that fell within the normal range (p < 0.001). D2 demonstrated values above the normal range for all but one sample, which does not satisfy the criteria of the Wilcoxon rank sum test for demonstrating significance (p = 0.089); however, ninety-nine samples displayed hypermagnesemia.

Conclusion: This study demonstrates that exogenous magnesium administration may not be necessary in the setting of our practice at CCHMC and dNC cardioplegic arrest.