Evaluation of standard versus prolonged magnesium infusion rates in hospitalized patients: a retrospective cohort study.

Background: Hypomagnesemia is a common electrolyte abnormality in hospitalized patients. Prolonging the infusion rate of magnesium has been hypothesized to increase retention of magnesium, however, there is limited evidence to support prolonging the rate of infusion.

Aim: To compare the absolute change in serum magnesium levels from baseline to levels drawn within 24 hours after the end of infusion between two groups receiving standard or prolonged infusion.

Methods: This was a retrospective, observational cohort study comparing patients receiving magnesium infusion at a standard rate of 0.5 gm/h to those receiving magnesium infusion at a prolonged rate of 0.17 gm/h.

Results: Of a total of 276 patients, 138 were included in each group. No differences existed between the groups for any demographic variables (all p>0.05). The absolute change in serum magnesium level was 0.41 mg/dL versus 0.31 mg/dL in the standard and the prolonged infusion groups, respectively (p = 0.001). The length of stay after the initial magnesium dose was slightly longer with the prolonged infusion compared to the standard infusion, with a median of 2.9 days versus 3.6 days, respectively (p = 0.02). No differences existed between the groups for any secondary or safety outcomes (all p>0.05).

Conclusion: Hospitalized general patients did not benefit from the prolonged infusion of magnesium compared to standard infusion.