Abstract 138: How Far is Too Far? A Decision Analysis Model of Pre-hospital Triage for Potential Large Vessel Occlusion Acute Stroke Patients

Abstract

Background and Purpose: We sought to determine when transporting patients directly to a comprehensive stroke center (CSC; the “mothership”) is favorable compared to a “drip-and-ship” approach while accounting for the varying predictive abilities of pre-hospital large vessel occlusion (LVO) screening methods. Methods: We built a decision analysis model to compare anticipated functional outcomes for patients who are within IV-tPA treatment window in “mothership” and “drip-and-ship”. Key branches included IV-tPA eligibility, IV-tPA only or endovascular therapy (ET), successful reperfusion after ET, and treatment effects. In terms of the probability of requiring ET, we assessed three pre-hospital LVO screening methods: no LVO screening, the Rapid Arterial oCclusion Evaluation (RACE) Scale for Stroke, and in-ambulance CT angiography for LVO. Good outcome was defined as mRS 0-1 and, secondarily, mRS 0-2. Imputed probabilities and workflow times were extracted from published studies. We used one-way and two-way sensitivity analyses to vary two key inputs: time from onset to arrival at primary stroke center (PSC) and additional travel time to CSC. Results: The relative benefit of the “mothership” approach varied with the likelihood of pre-hospital LVO identification for outcome of mRS 0-1. In the absence of pre-hospital LVO screening, “drip-and-ship” was always favored. When pre-hospital CT angiography is used, “mothership” is always favored. When modeling the use of the RACE Scale for patients with onset-to-PSC arrival time less than 70 minutes, “mothership” was favored if the additional travel time to CSC was less than 21 minutes. When onset-to-PSC arrival time passed 70 minutes, “mothership” was favored for additional travel times up to 48 minutes (Figure). Conclusion: The results of our decision analysis model suggest that, in addition to transport times, pre-hospital LVO screening and time from stroke onset could influence triage decision making.