Ram et al. suggested that magnesium sulfate has a role in the treatment of subarachnoid hemorrhage-induced vasospasm in humans ¹⁾.

Boet et al. established in 2000 administration guidelines for the use of MgSO4 in aneurysmal SAH but appointed that a prospective double-blind placebo-controlled trial is required to establish the effectiveness of MgSO4 for treating vasospasm in aneurysmal SAH ²⁾.

Brewer et al. studied the effect of magnesium as a cerebral vasodilator by measuring the cerebral blood flow velocity (CBFV) response to a 5g intravenous bolus of MgSO4 compared with a saline placebo after subarachnoid hemorrhage (SAH). Transcranial Doppler ultrasonography of the middle cerebral artery (MCA) was measured after each infusion. Patients were studied up to three times after SAH at prescribed time intervals. Fourteen patients (11 women, 3 men; mean age 58 years) underwent 29 studies. All patients underwent hypertensive, hypervolemic therapy. Four patients developed cerebral vasospasm. Doubling serum magnesium levels did not affect MCA CBFV but slightly lowered mean arterial blood pressure and systemic vascular resistance. Intravenous magnesium bolus did not reduce elevated CBFV in the subset of SAH patients with clinical vasospasm. The role of magnesium sulfate as a cerebral vasodilator in patients with SAH requires further study ³⁾.

Administration of high-dose MgSO4 following aneurysmal SAH is safe, and steady Mg++ levels in the range of 4 to 5.5 mg/dl are easily maintained. This treatment does not interfere with neurological assessment, administration of anesthesia during surgery, or other aspects of clinical care. Veyna et al. observed a trend in which a higher percentage of patients obtained GOS scores of 4 or 5 in the group treated with MgSO4, but the trend did not reach a statistically significant level ⁴⁾.

A systematic review was conducted to determine the evidence for the prophylactic use of magnesium sulfate in aneurysmal subarachnoid hemorrhage. Medline, Embase, Cochrane library, clinicaltrials.gov, and controlled-trials.com were searched with a comprehensive search strategy. 2,035 records were identified in the initial search and 1,574 remained after removal of duplicates. Randomized, parallel group, controlled trials of magnesium sulfate in patients with aneurysmal subarachnoid hemorrhage were included. A total of ten studies were included. Review Manager and GRADE software were used to synthesize the results. The summary effect for Glasgow outcome scale and the modified Rankin scale is a risk ratio (RR) of 0.93 [95 % confidence interval (CI) 0.82-1.06]. The RR for mortality is 0.95 [95 % CI 0.76-1.17]. Delayed cerebral ischemia has a RR of 0.54 [95 % CI 0.38-0.75], which is the only outcome with a statistically significant summary effect measure favoring magnesium treatment. Delayed ischemic neurological deficit has a RR of 0.93 [95 % CI 0.62-1.39]. Transcranial doppler vasospasm has a RR of 0.72 [95 % CI 0.51-1.03]. Current evidence does not support the prophylactic use of magnesium sulfate in aneurysmal subarachnoid hemorrhage ⁵⁾.

Currently, the only treatment strategy to reduce the risk of delayed cerebral ischaemia remains nimodipine; there is no place for magnesium sulphate ^{6) 7)}.

Continuous cisternal irrigation with MgSO4 solution starting on Day 4 and continuing to Day 14 significantly inhibited cerebral vasospasm CV in patients with aneurysmal subarachnoid hemorrhage (SAH) without severe cardiovascular complications. However, this improvement in CV neither reduced the incidence of delayed cerebral ischemia nor improved the functional outcomes in patients with SAH ⁸⁾.

Magnesium treatment did not reduce the risk of delayed cerebral ischemia in patients with aneurysmal subarachnoid hemorrhage, nor was there an interaction with glucose levels. It is therefore unlikely that glucose levels explain the failure of magnesium to prevent delayed cerebral ischemia and poor outcome after aneurysmal subarachnoid hemorrhage ⁹⁾.

Current evidence does not support the prophylactic use of magnesium sulfate in aneurysmal subarachnoid hemorrhage ¹⁰⁾.

It is disappointing that recent randomized, controlled trials did not demonstrate that the vasodilator magnesium sulfate improve patient outcome ¹¹⁾.