Plasma magnesium concentrations and clinical outcomes in aneurysmal subarachnoid hemorrhage patients: post hoc analysis of intravenous magnesium sulphate for aneurysmal subarachnoid hemorrhage trial.

BACKGROUND AND PURPOSE: Conflicting data have been obtained on optimal plasma magnesium concentrations for clinical outcomes in patients with aneurysmal subarachnoid hemorrhage.

METHODS: Adults (aged 18 years or older) who had acute aneurysmal subarachnoid hemorrhage diagnosed were randomly assigned to receive either an intravenous MgSO(4) infusion (80 mmol in 500 mL normal saline per day) or a placebo (500 mL normal saline per day) for up to 14 days. Post hoc multivariable binary logistic regression analyses were performed by dividing mean plasma magnesium concentrations into 4 quartiles according to treatment group and then comparing with the lowest quartiles.

RESULTS: The worst clinical outcomes at 6 months were seen in MgSO(4) group patients, with mean plasma magnesium concentrations in the fourth quartile, and in placebo group patients, with mean such concentrations in the third and fourth quartiles.

CONCLUSIONS: No evidence was found to suggest that a higher mean plasma magnesium concentration improves clinical outcomes. On the contrary, we found an association between high plasma magnesium concentration and worse clinical outcomes.