INTRODUCTION: Cerebral vasospasm in aneurysmal subarachnoid hemorrhage (SAH) is 
associated with poor outcome. The safety and feasibility of continuous high-dose 
intravenous magnesium sulfate (MgSO4) for the prevention of cerebral vasospasm 
and ischemic cerebral injury has not been well studied.
METHODS: Patients presenting to our center within 72 hours of aneurysmalSAH 
(confirmed by computed tomography [CT] scanning and cerebral angiography) 
between June 2001 and October 2002 were enrolled in a prospective pilot study in 
which they received MgSO4 as an adjunct to standard SAH management. Study 
patients received an intravenous infusion of 12 g of MgSO4 in a 500-mL solution 
of 0.9% NaCl administered at a rate of 4.06 mM (or 0.5 g) every hour over a 
24-hour period for 10 days to achieve a target predetermined serum Mg range of 
more than 1.5 to less than 4.0 mM/L. The effect of MgSO4 on clinical 
examination, heart rate, and blood pressure was measured every 2 hours; serum 
glucose and phenytoin levels were monitored daily. Outcome measures included 
evidence of vasospasm on clinical examination, transcranial Doppler study 
((TCD); velocity >or=100 cm/s), or repeat cerebral angiogram obtained within 10 
days of SAH; and Glasgow Outcome Scale (GOS) score assessment and CT scan 
evidence of ischemic infarction at 30 days.
RESULTS: Nineteen patients (mean age: 55 years; range: 39-84 years; 11 males, 8 
females) were enrolled in the study. Presenting Hunt Hess grade was II or 
higher; mean Fisher grade was 3. Vasospasm was observed in nine patients (by 
clinical examination in two, TCD in five, and angiogram in nine). The mean serum 
Mg level was 2.7 mM/L (standard deviation: +/- 0.37) and was maintained during 
the infusion period. No clinical adverse effects, hemodynamic changes, or 
fluctuations in serum glucose or phenytoin levels were observed. None of the 
patients died; no CT evidence of ischemic infarction was present; and most had 
good outcomes (GOS 5 in 10 patients; GOS 4 in 8 patients).
CONCLUSION: Our study confirmed the safety and feasibility of a continuous 
infusion of high-dose intravenous MgSO4 in patients with aneurysmal SAH. 
Randomized controlled trials are required to confirm the promising results.