Magnesium levels, magnesium supplementation and neurological outcome following cardiac arrest

From a poster presentation at AHA 2016:

Introduction: Therapeutic hypothermia (TH) improves neurological outcomes after cardiac arrest by mitigating cerebral reperfusion injury. Plasma magnesium (Mg) inhibits glutamate release, restores blood brain barrier integrity and decreases brain edema. The neuroprotective role of Mg in cardiac arrest patients undergoing TH is not well established. We sought to determine the relationship of plasma Mg and neurologic outcomes in these patients.

Methods: A cohort of 384 consecutive patients who completed TH (33°C) from 2007 to 2016 was retrospectively studied. We evaluated favorable neurologic outcomes as a function of Mg levels before, during, and after TH as well as the relationship between neurologic outcomes and Mg supplementation during TH…

Patients with favorable neurologic outcomes had lower Mg levels at presentation (2.1 mEq/L vs. 2.2 mEq/L, p=0.031). Mg levels on presentation inversely correlated with favorable neurologic outcomes (r=-0.107). A larger percentage of patients who received magnesium supplementation had favorable neurologic outcomes (33% vs. 22%, p=0.033). We also stratified patients based on Mg levels in increments of 0.2 mEq/L to evaluate neurologic outcomes. A non-statistically significant trend towards worse neurologic outcomes was noted in patients with Mg less than 1.6 mEq/L at 24 hours and greater than 2.7 mEq/L at 24 and 48 hours…

Discussion: Lower Mg levels at presentation and magnesium supplementation during TH were associated with favorable outcomes. Intracellular shift and increased renal excretion of Mg have been associated with TH and could worsen hypomagnesemia on presentation after a cardiac arrest. Mg supplementation may potentiate the beneficial effects of TH.