Impact of intravenous magnesium infusion rate during ambulatory replacements on serum magnesium concentrations after allogeneic stem cell transplant

Evaluation of prolonged magnesium infusion after allogeneic hematopoietic cell transplant

PURPOSE

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.

METHODS

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.

RESULTS

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.

CONCLUSIONS

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

Prolonged Versus Short Infusion Rates of IV Magnesium in Hospitalized General Medicine Patients with Hypomagnesemia

Introduction: Due to the renal handling mechanism of magnesium, prolonging the time for infusion of intravenous (IV) magnesium has been postulated to decrease magnesium requirements; however, a paucity of clinical evidence exists to support prolonging infusion rates. Objective: To assess if there is a difference in magnesium replacement required in the medicine population at an academic medical center when prolonged infusion rates (0.5 g/h) are compared to short infusion rates of > 0.5 g/h. Methods: A retrospective chart review was performed before and after implementation of the hypomagnesemia protocol (November 2015). Patients who received at least one dose of IV magnesium during hospitalization were selected from general medicine units. Primary aim was to determine if a difference exists in percent of days IV magnesium repletion required between patients receiving prolonged versus short infusion rates. Secondary objectives were to determine if a difference exists in total grams of magnesium received, percent of days magnesium levels were maintained in the optimal (1.4-2.7) and desired (2-2.7) therapeutic ranges, and incidence of hypomagnesemia (< 1.4 g/dL) and hypermagnesemia (> 2.7 g/dL). For safety, incidence of hypotension (systolic blood pressure < 90/60 mm Hg) during the magnesium infusion was recorded. Results: Totally, 45 patients were included in each cohort for a total of 90 patients to meet power. No differences existed between protocol groups for any demographic variables (all P > .05). Median infusion rate for the short infusion cohort was 1.8 g/h (range 1-2 g/h). Percent of days IV magnesium was replaced was 34.8% versus 37.8% (P = .39) in the short and prolonged infusion groups, respectively. No difference existed between groups for secondary outcomes (all P > .05). Conclusion: Prolonged magnesium infusion rates did not decrease magnesium replacement requirements. These results have been used to propose revision of our current magnesium infusion protocol to reduce infusion length.

Prolonged versus short infusion rates for intravenous magnesium sulfate administration in hematopoietic cell transplant patients

PURPOSE

Hematopoietic cell transplant (HCT) recipients often require intravenous (IV) magnesium repletion due to poor dietary intake, gastrointestinal loss, and use of concomitant magnesium wasting medications. Prolonging the IV magnesium infusion rate has been postulated to reduce renal clearance and improve retention; however, limited evidence supports this hypothesis.

METHODS

We reviewed autologous and allogeneic HCT recipients (n = 82) who received IV magnesium at our institution between 2014 and 2016: 41 patients received IV magnesium at a prolonged rate of 0.5 g/h and 41 patients at > 0.5 g/h (mean 2.07 g/h). Primary outcome was percent of days in which magnesium levels were in desired therapeutic range (2-2.7 mg/dL) during hospitalization.

RESULTS

Baseline characteristics were similar between cohorts: no difference existed between groups in incidence of gastrointestinal graft-versus-host disease or the percentage of patients who received magnesium replacement in maintenance fluids, received concomitant oral magnesium supplementation, or received parenteral nutrition. Percent of days in desired therapeutic range was not different between groups (p = 0.3). No difference existed between groups with respect to total amount of IV magnesium repletion (22.5 vs. 21.4 g, p = 0.81) or number of days of IV replacement (7.2 vs. 6.2 days, p = 0.41). In terms of safety, there was no difference between groups with respect to incidence of hypomagnesemia or hypermagnesemia (p = 0.43 each).

CONCLUSIONS

Overall, prolonging the infusion rate did not correlate with improved magnesium retention based on amount and frequency of magnesium repletion or attainment of goal levels in HCT patients.