Early targeted magnesium administration improved TCD-derived hemodynamic markers during the peak vasospasm window; however, it did not significantly reduce CV incidence, DCI, ICU or hospital stay, or 30-day functional outcome.
Key Findings
Results
Magnesium sulfate administration did not significantly reduce the overall incidence of cerebral vasospasm compared to placebo in aSAH patients.
121 aSAH patients were randomized to IV MgSO4 or placebo within six hours of admission
The primary outcome was incidence of CV assessed by transcranial Doppler (TCD)
No significant difference was found in overall CV incidence between the Mg and placebo groups
The trial was conducted across four neurocritical care units in Korea between 2019 and 2024
Results
The magnesium group demonstrated significantly lower mean flow velocity and Lindegaard ratio on days 4–9, indicating reduced vasospasm severity during the peak vasospasm window.
Reduced vasospasm severity was measured by TCD-derived hemodynamic markers
The reduction in mean flow velocity and Lindegaard ratio was observed specifically during days 4–9 post-admission
Days 4–9 correspond to the peak vasospasm window following aneurysmal SAH
These differences were statistically significant despite no overall difference in CV incidence
Results
A median serum magnesium concentration greater than 2.5 mg/dL during the first 14 hospital days was independently associated with lower risks of both cerebral vasospasm and delayed cerebral ischemia.
This finding came from exploratory multivariable analyses
The target serum magnesium range for the intervention was 2.0–3.0 mg/dL, maintained for 14 days
The threshold of >2.5 mg/dL was identified as the relevant concentration for risk reduction
The association was independent of other variables in multivariable modeling
Results
Magnesium administration showed no significant differences in functional outcomes, ICU length of stay, hospital length of stay, or serious adverse events compared to placebo.
Functional outcome was assessed using the modified Rankin Scale (mRS) at 30 days
No significant differences were found in mRS scores between the Mg and placebo groups
ICU and hospital length of stay did not differ significantly between groups
Serious adverse events were not significantly different between treatment arms
Methods
The study was a prospective, multicenter, single-blind randomized controlled trial targeting serum magnesium levels of 2.0–3.0 mg/dL initiated within six hours of aSAH admission.
Conducted across four neurocritical care units in Korea between 2019 and 2024
121 aSAH patients were enrolled and randomized
IV MgSO4 was infused to maintain serum concentrations between 2.0 and 3.0 mg/dL for 14 days
Treatment was initiated within six hours of hospital admission
The study was single-blind in design
What This Means
This research suggests that giving magnesium sulfate intravenously to patients shortly after a brain aneurysm rupture (subarachnoid hemorrhage) does not prevent the overall occurrence of dangerous arterial narrowing (cerebral vasospasm) or the brain injury it can cause (delayed cerebral ischemia). The study enrolled 121 patients across four hospitals in Korea, starting magnesium infusions within six hours of hospital admission and maintaining elevated magnesium levels in the blood for two weeks.
However, the study did find that magnesium treatment reduced the severity of vasospasm during the most critical window — days 4 through 9 after the bleed — as measured by blood flow markers on ultrasound. Additionally, a deeper analysis suggested that patients who maintained higher magnesium levels (above 2.5 mg/dL on average) had lower risks of both vasospasm and delayed brain injury, hinting that the exact magnesium concentration achieved may matter. There were no meaningful differences in patient recovery scores at 30 days, time spent in the ICU or hospital, or rates of serious side effects between the magnesium and placebo groups.
This research suggests that while magnesium may dampen the intensity of vasospasm during a key danger period, it does not translate into measurable improvements in patient outcomes at the doses and targets studied. The findings raise the possibility that achieving higher, more precise magnesium blood levels could be important, but this would need to be confirmed in future trials specifically designed to test that question.
Kim M, Kim J, Jung H, Kim S, Hwang J, Jeon H, et al.. (2026). Magnesium administration for vasospasm prevention in acute aneurysmal SAH: a multicenter randomized controlled trial.. Neurosurgical review. https://doi.org/10.1007/s10143-026-04470-z