The cardioplegia solution of choice in many pediatric cardiac congenital programs is the del Nido solution. While many cardioplegia solutions provide diastolic arrest, del Nido provides a longer period of time between doses of cardioplegia. Many of the other cardioplegia solutions do not incorporate magnesium into the constituents, but del Nido does. Routine practice at CCHMC is to dose 25 mg/kg magnesium upon removal of the heart cross-clamp to protect against hypomagnesemia and associated arrhythmias. However, with the incorporation of magnesium in the del Nido solution, it may not be necessary to administer magnesium post cross-clamp and it could in fact be detrimental if the magnesium level is too high. This observational study will examine the magnesium levels prior to and after cross-clamp removal under our current process. The magnesium levels measured after the administration of del Nido cardioplegia and prior to cross-clamp removal will help inform our current practice.

Inclusion Criteria:

• Patients undergoing cardiac surgery requiring CPB and cardioplegic arrest with del Nido cardioplegia solution.
• Patients planned to receive post cross-clamp dose of 25 mg/kg magnesium sulfate.

All patients undergoing CPB with dNC cardioplegic arrest.