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.
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