Abstract TMP12: Does Prehospital Magnesium Sulfate Differentially Improve Outcome in Hyperacute Stroke Patients With Higher Pretreatment Blood Pressure?
Introduction: Magnesium sulfate (Mg) has blood pressure (BP) lowering, cerebral blood flow enhancing, and neuroprotective effects in preclinical and clinical studies. In the IMAGES phase 3 trial, Mg up to 12h after onset showed no benefit in acute stroke, but was associated with improved outcome in patients with higher blood pressure at entry. Hypothesis: We tested the hypothesis that ultra-early Mg improves functional outcome in acute stroke patients with higher baseline BP. Methods: FAST-MAG is a multicenter, double-blind, randomized, placebo-controlled trial of paramedic-initiated Mg, administered to patients with suspected stroke within 2h of symptom onset. The primary analysis showed neutral effect of Mg. This secondary analysis examines rates of functional independence (mRS 0-2) at 3m for Mg and placebo for different field BP groups. Results: Among 1622 patients with acute cerebrovascular disease, age was 69.6 (±13.4), 42% female, entry deficit severity in the field was LAMS 3.8 (±1.2), and first post-enrollment NIHSS in the ED was 11.5 (±9.9). Systolic blood pressure prior to enrollment was higher among patients with intracerebral hemorrhage (ICH) than acute cerebral ischemia (ACI), 175 (±25) vs 155 (±27), p < .001. The Figure shows the Forest plot for Mg vs placebo and functional independence among blood pressure groups. Heterogeneity of treatment effect was noted in the all-cerebrovascular patients population (p < .01), with fewer independent outcomes with Mg than placebo among patients with higher entry BPs. Analysis of Functional Independence (mRS 0-2) at 90 Days in Prespecified Subgroups Conclusion: This analysis did not confirm the prior finding of magnesium sulfate benefit among acute stroke patients with elevated blood pressure (and actually provided a signal in the opposing direction). Mg was not demonstrated to improve outcome when started in the first 2h of onset among patients with acute cerebrovascular disease and higher blood pressures.