Magnesium in aneurysmal subarachnoid hemorrhage (MASH II) phase III clinical trial MASH-II study group.

RATIONALE: Delayed cerebral ischemia (DCI) is an important cause of poor outcome after aneurysmal subarachnoid hemorrhage (SAH). Magnesium is a neuroprotective agent that acts as an NMDA-receptor antagonist and a calcium channel blocker. In a phase II randomized clinical trial of 283 patients, magnesium treatment reduced the risk of DCI by 34% and of poor outcome by 23%.

AIMS: To determine whether magnesium improves clinical outcome in patients with aneurysmal SAH.

DESIGN: The MASH-II study is a phase III randomized, clinical international multicenter trial. Magnesium sulfate 64 mmol/day (equals 16 g/day) or placebo is started intravenously within 4 days after the SAH and is continued until 20 days after the hemorrhage. The primary outcome measure is poor outcome, defined as death or dependence (Rankin score >3) after 3 months. We aim to include 1200 patients in 5 years.

STUDY OUTCOMES: Primary outcome will be poor clinical outcome as measured by the modified Rankin scale at 3 months.