• The primary endpoint is the modified Rankin Scale global measure of functional outcome, assessed 90 days after treatment. [ Time Frame: 3 months after stroke onset ] [ Designated as safety issue: No ]
  

Stroke is the third leading cause of death and the leading cause of adult disability in the United States. Each year, more than 750,000 Americans suffer a symptomatic stroke.

Currently, rt-PA is the only approved treatment for acute ischemic stroke; however, its usefulness is limited because most patients cannot reach medical attention within the necessary 3-hour time window. In addition, rt-PA cannot be given in the field because it is contraindicated for treatment of patients with brain hemorrhage.

The purpose of this multi-center, randomized, double-blind trial is to demonstrate that paramedic initiation of the neuroprotective agent magnesium sulfate in the field is an effective and safe treatment for acute stroke. This study will analyze magnesium sulfate, an experimental therapy for stroke, versus placebo among ambulance-transported patients with acute stroke. This trial will also demonstrate that paramedics can safely, effectively, and rapidly start neuroprotective therapies for stroke.

Inclusion Criteria:

• Suspected stroke identified by the Los Angeles Prehospital Stroke Screen
• Age 40-95, inclusive
• Last known well time within 2 hours of treatment initiation
• Deficit present for >/= 15 minutes

Exclusion Criteria:

• Coma
• Rapidly improving neurologic deficit
• Pre-existing neurologic, psychiatric, or advanced systemic disease that would confound the neurological or functional outcome evaluations
• SBP < 90 or > 220
• Known severe renal dysfunction (on dialysis or known chronic creatinine > 3.0)
• Severe respiratory distress (O2 sat < 90% or respiratory rate < 12 or >/= 24)
• Known second or third degree heart block with no pacemaker in place
• Major head trauma in the last 24 hours
• Recent stroke within prior 30 days
• Patient unable to give informed consent and no available legally authorized representative to provide informed consent