Prehospital use of magnesium sulfate as neuroprotection in acute stroke.

Multicenter randomized, placebo-controlled prehospital trial of adults with suspected acute stroke in Los Angeles and Orange Counties, California. Paramedics initiated treatment within 2 hours of symptom onset across 60 hospital sites and 315 paramedic-staffed ambulances, with 857 participants in the magnesium sulfate arm.

Magnesium sulfate was given intravenously as a 4 g bolus in 54 mL normal saline over 15 minutes in the field, followed by 16 g in 240 mL 0.9% normal saline infused at 10 mL/hour for 24 hours. Treatment was started prehospital after suspected stroke, with maintenance continued after arrival in the emergency department; comparator was placebo.

Prehospital magnesium sulfate was safe and feasible, but it did not improve 90-day functional outcome after acute stroke. The 90-day global Rankin distribution showed no significant shift versus placebo (P = 0.28), and mean Rankin scores were identical at 2.7 in both groups (P = 1.00). Key secondary outcomes were also neutral, including minimal or no disability (36.5% vs 36.9%; OR 0.98, 0.81-1.20), functional independence (52.4% vs 52.8%; OR 0.98, 0.81-1.19), and death (15.4% vs 15.5%; P = 0.95). Serious adverse events were similar between groups (51.2% vs 50.1%; P = 0.67), with no signal of benefit on neurologic recovery.

The trial enrolled patients with suspected stroke before definitive diagnosis, so the population included intracranial hemorrhage and stroke mimics as well as ischemic stroke. Despite a large prehospital protocol, the intervention produced no efficacy signal on the primary or major secondary outcomes, limiting support for routine neuroprotective use in this setting.