Evaluation of prolonged magnesium infusion after allogeneic hematopoietic cell transplant

Calcineurin inhibitor use after allogeneic hematopoietic cell transplantation (allo-HCT) is associated with significant magnesium wasting. Utilization of a prolonged magnesium infusion is thought to lead to a lower serum peak concentration and therefore, decreased renal wasting of magnesium. In November 2017, our institution implemented a modification to our inpatient electrolyte replacement protocol for allo-HCT recipients that extended the magnesium infusion rate from 4 g/2 h to 4 g/4 h based on this theoretical advantage. The primary objective of this study was to compare the median magnesium requirements per day of admission between patients who received magnesium 4 g/2 h to patients who received magnesium 4 g/4 h. Secondary objectives included a comparison of the per-patient median serum magnesium concentration during admission, as well as the median incremental difference in serum magnesium concentration after intravenous replacement per patient per admission.

Allo-HCT recipients who received prolonged infusion magnesium infusions were compared to a historical cohort of allo-HCT patients who received shorter IV magnesium infusions. Admissions were included if the patient had received an allo-HCT within 100 days prior, was admitted to the Transplant and Cellular Therapy Unit at WVU Medicine J.W. Ruby Memorial Hospital, and received at least one magnesium infusion and one dose of cyclosporine or tacrolimus. Admissions were excluded if the patient received oral magnesium, total parenteral nutrition, aminoglycosides, amphotericin, carboplatin, cisplatin, or foscarnet.

The pre-implementation group consisted of 81 admissions (n = 64 patients), while the post-implementation group consisted of 90 admissions (n = 60 patients). Median magnesium requirements per day of admission were not different between groups at 1.4 g of magnesium in the pre-implementation group and 1.9 g of magnesium in the post-implementation group (P = 0.25). Median serum magnesium concentrations and median incremental difference in serum magnesium concentration after intravenous replacement were also not different between groups: 1.65 mg/dL vs 1.60 mg/dL (P = 0.65) and 0.30 mg/dL vs 0.28 mg/dL (P = 0.67), respectively.

Prolonged infusion of magnesium in allo-HCT recipients receiving CNI therapy does not result in improvement in magnesium retention.