Comparison of extended infusion versus standard infusion magnesium repletion in adult trauma intensive care unit patients

Introduction:

Hypomagnesemia can be detrimental in intensive care unit (ICU) patients, and rapid infusion times may cause increased renal excretion.  There is minimal evidence on best practice for repleting magnesium, with standard infusion rates of 1 gram over 30 minutes to an hour.

Objectives:

The primary endpoint of this study is to determine if there is a difference in the effectiveness of magnesium repletion, measured by change in serum magnesium level per gram of magnesium administered, in trauma ICU subjects who received intravenous magnesium via extended infusion (>1g per hour) compared to standard infusion (≤1g per hour).

Study Design:

This is a retrospective, single-center comparison of trauma ICU patients receiving standard versus extended intravenous magnesium sulfate for magnesium repletion from January 2013 to October 2015.

Methods:

Extended infusions are randomly matched to standard infusions according to baseline magnesium (<1.0; 1.0-1.4; 1.5-1.9mg/dL) and glomerular filtration rate (30-59; 60-89; ≥90mL/min/1.73m^2) of the recipients. To achieve 80% power and detect a difference in magnesium of 0.17mg/dL, 400 infusions (200 per arm) are required. Exclusions include renal impairment, enteral repletion, TPN, preeclampsia or vasospasm. Confounders will be evaluated including loop diuretics and fluid balance. Secondary endpoints include the percentage of doses that increased magnesium to ≥2.0mg/dL and the change in serum potassium.

Results:

Preliminary results comparing 20 infusions in each arm resulted in a higher mean change in serum magnesium level per gram of magnesium administered with extended than standard infusions (0.201mg/dL vs 0.145mg/dL). Additionally, lower doses of magnesium were given in the extended than standard arm (2.2g vs 2.8g).

Conclusions:

Data collection is underway and will be completed by March 2016. Preliminary results suggest extended infusion magnesium repletion could produce greater efficacy while utilizing fewer doses. Final results could allow for standardization of electrolyte repletion in a trauma ICU setting.