Abstract 101: Prehospital Study Enrollment Enables Initiation of Neuroprotective Agent for Acute Stroke in Hyperacute Time Windows

Background: As “time lost is brain lost” in acute ischemic stroke, earlier start of therapy will maximize access of promising drugs to salvageable brain tissue. We hypothesized that prehospital treatment initiation would accelerate treatment delivery of neuroprotective agent in a prehospital randomized clinical trial. Methods: We analyzed research treatment initiation times in consecutive patients enrolled in the NIH Field Administration of Stroke Therapy – Magnesium (FAST-MAG) Phase 3 clinical trial. In FAST-MAG, patients with suspected acute stroke within 2 hours of onset are randomized to paramedic initiation of magnesium sulfate or placebo in 358 participating ambulances and 59 receiving hospitals. Results: Among 1486 patients, mean age was 69 (SD13.7), 42% were female, median pretreatment Los Angeles Motor Scale score was 4, and final diagnosis was acute cerebral ischemia in 71.9%, intracranial hemorrhage in 24.4%, and stroke mimic in 3.7%. Figure 1 shows the distribution of values for time from onset (last known well) to treatment (OTT). Clustering of experimental treatment start times at the maximum permitted time window, common in in-hospital stroke trials, was not seen in this cohort with prehospital care mandated early transports. Across all patients, the median OTT was 49.0 minutes. 73.5% of patients were treated within the first 60 minutes of onset (the “golden hour”) and 10.8% within the first 30 minutes of onset. Mean time from paramedic arrival on scene to start of treatment was 23.0 (SD 7.6) minutes, and 4.3% of patients were treated within 10 minutes of medic arrival (the “platinum ten minutes”). Conclusions: Prehospital initiation enables start of experimental neuroprotective therapy in times previously not achievable in acute stroke treatment trials. Nearly three-quarters of patients can be treated within the golden hour and more than one in ten within the first 30 minutes of onset.