Effect of Mobile Stroke Unit Dispatch in all Patients with Acute Stroke or TIA

Abstract

Objective: To determine the effect of additional mobile stroke unit (MSU) dispatch on functional outcomes among the full spectrum of stroke patients, regardless of subtype or potential contraindications to reperfusion therapies.

Methods: We used data from the nonrandomized Berlin-based B_PROUD study (02/2017 to 05/2019), in which MSUs were dispatched based solely on availability, and the linked B-SPATIAL stroke registry. All patients with final stroke or transient ischemic attack (TIA) diagnoses were eligible. The intervention under study was the additional dispatch of an MSU, an emergency physician-staffed ambulance equipped to provide prehospital imaging and thrombolytic treatment, compared to conventional ambulance alone. The primary outcome was the 3-month modified Rankin Scale (mRS) score, and the co-primary outcome was a 3-tiered disability scale. We identified confounders using directed acyclic graphs and obtained adjusted effect estimates using inverse probability of treatment weighting.

Results: MSUs were dispatched to 1,125 patients (mean age: 74 years, 46.5% female), while for 1,141 patients only conventional ambulances were dispatched (75 years, 49.9% female). After confounding adjustment, MSU dispatch was associated with more favorable 3-month mRS scores (common odds ratio [cOR] = 0.82; 95% confidence interval [CI]: 0.71-0.94). No statistically significant association was found with the co-primary outcome (cOR = 0.86; 9% CI: 0.72-1.01) or 7-day mortality (OR = 0.94; 95% CI: 0.59-1.48).

Interpretation: When considering the entire population of stroke/TIA patients, MSU dispatch improved 3-month functional outcomes without evidence of compromised safety. Our results are relevant for decision-makers since stroke subtype and treatment eligibility are unknown at time of dispatch.