Magnesium Levels and Neurologic Outcomes in Patients Undergoing Therapeutic Hypothermia After Cardiac Arrest

Abstract

Therapeutic hypothermia (TH) improves neurological outcomes after cardiac arrest by mitigating cerebral reperfusion injury. Serum 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 analyzed 438 survivors of cardiac arrest who completed a TH protocol from 2008 through 2016. Multivariate and receiver operating characteristic (ROC) analyses examined the association between Mg supplementation and Mg levels before, during, and after TH with neurologic outcomes. Participants were 65.5 ± 15.9 years old, 47% received bystander cardiopulmonary resuscitation, and time to target temperature was 286 ± 196 minutes. Patients with favorable neurologic outcomes had lower Mg levels at presentation (2.1 mg/dL vs. 2.2 mg/dL, p = 0.010; OR [95% CI] = 0.531 [0.329-0.857]) and more frequently received Mg supplementation (39% vs. 25%, p = 0.009; OR [95% CI] = 1.936 [1.171-3.202]). Mg levels on presentation inversely correlated with favorable neurologic outcomes (r = -0.134, p = 0.036). Stratification of patients based on Mg levels demonstrated trends toward worse neurological outcomes at the extremes of the range, though sample sizes were small and the point estimate was not significant. ROC analysis showed no significant Mg level determining favorable outcomes. Mg levels at presentation inversely correlated with neurologic outcomes in cardiac arrest survivors undergoing TH. Intracellular shift and increased renal excretion of Mg may be responsible for the low Mg levels seen in some patients undergoing TH. Whether Mg supplementation could potentiate the beneficial effects of TH remains unclear and deserves further investigation.

The role of magnesium in cardiac arrest

“…Analysis of 438 survivors of cardiac arrest who completed a therapeutic hypothermia protocol, showed that lower magnesium levels at presentation and during therapeutic hypothermia were associated with favorable outcomes of cardiac arrest. Moreover, magnesium supplementation during the hospital stay was associated with improved neurological outcomes, suggesting that magnesium supplementation may potentiate the beneficial effects of therapeutic hypothermia ( 38 ). Several mechanisms explain why magnesium and hypothermia appear to act synergistically.…”

Electrolyte profiles with induced hypothermia: A sub study of a clinical trial evaluating the duration of hypothermia after cardiac arrest

“…8 Hypomagnesaemia has also been associated with poor neurologic outcomes in patients suffering from post-cardiac arrest syndrome (PCAS). 9 Other electrolytes are also of importance in this context. Hypocalcaemia can cause reduced cardiac contractility and decreased vascular tone, 10 while hypophosphatemia can cause muscle weakness and reduced diaphragmatic contractility, leading to difficulties weaning from a ventilator.…”

“…Magnesium plays an important role in many cellular functions, and hypomagnesemia may induce cardiac arrhythmias and interfere with vascular tone 8 . Hypomagnesaemia has also been associated with poor neurologic outcomes in patients suffering from post‐cardiac arrest syndrome (PCAS) 9 . Other electrolytes are also of importance in this context.…”