306: SAFETY AND EFFICACY OF FIXED-DOSE MAGNESIUM REPLACEMENT

Abstract

Introduction: Magnesium (mag) deficiency occurs in up to 65% of patients in the intensive care unit and up to 20% of all hospitalized patients. Magnesium replacement dosing varies due to the lack literature. In 2019, our institution switched to a fixed dose of magnesium sulfate intravenous (IV) 4g for all IV doses of magnesium for treatment of hypomagnesemia including ICU and renal impairment patients. Methods: This is a retrospective, single-center, IRB approved study at a large tertiary referral hospital from 1/2018 to 8/2019. Patients were divided into two groups: pre (1/2018–6/2018) & post (1/2019–8/2019) implementation of fixed dose mag protocol. The pre group received an initial mag replacement of 2g IV and the post group received mag IV 4g for hypomagnesemia. Patients were included if they received mag IV 2g or 4g dose (depending on the time period) and excluded for lack of follow-up levels. The primary endpoint was mag level at 48h. Secondary outcomes included incidence of mag toxicity and total grams of mag in a 96 hour period. A subgroup analysis of patients with impaired renal function was conducted. Statistics were performed in SPSS version 28. Results: A total of 2,440 patients were included with 934 in the 2g cohort and 1506 in the 4g cohort. The cohorts were similar with 40% of the patients having a eGFR < 60 mL/min/1.73m2 and 7% with an eGFR < 15 mL/min/1.73m2. The 4g cohort had a statistically significant higher mag level at 48h (1.91 mg/dL vs 1.98 mg/dL, p=0.001), 24h (1.97 mg/dL vs 2.19 mg/dL, p=0.001), 72h (1.90 mg/dL vs 1.98 mg/dL, p=0.001), and 96h (1.88 mg/dL vs 1.96 mg/dL, p=0.001) compared to the 2g cohort. The 2g cohort required significantly more doses of mag vs the 4g cohort (mean doses/patient: 1.97 vs. 1.70, p=0.001), and received fewer grams (mean grams/patient: 3.98g vs 6.44g, p=0.001). No patients in the 2g and one in the 4g cohort had a mag level > 4.5 mg/dL, but did not have any signs of toxicity upon chart review. In the subgroup analysis of renal impairment, there were no differences in mag levels at any time point. Conclusions: Using a fixed dose magnesium IV 4g doses instead of 2g doses led to statistically significant higher levels, but may not be clinically significant. This protocol appears safe for ICU patients, and patients with renal impairment.