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Original Investigation
December 2018

Modeling Stroke Patient Transport for All Patients With Suspected Large-Vessel Occlusion

Author Affiliations
  • 1Department of Community Health Sciences, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
  • 2Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
  • 3Alberta Children’s Hospital Research Institute & O’Brien Institute for Public Health, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
  • 4Department of Clinical Neurosciences, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
  • 5Calgary Stroke Program, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
  • 6Department of Medicine and Neurology, Royal Melbourne Hospital, Parkville, Australia
  • 7Student, Department of Chemical and Petroleum Engineering, Schulich School of Engineering, University of Calgary, Calgary, Alberta, Canada
  • 8Student, Department of Mechanical and Manufacturing Engineering, Schulich School of Engineering, University of Calgary, Calgary, Alberta, Canada
  • 9Department of Radiology, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
  • 10Department of Medicine, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
  • 11Department of Electrical and Computer Engineering, Schulich School of Engineering, University of Calgary, Calgary, Alberta, Canada
  • 12Department of Mechanical and Manufacturing Engineering, Schulich School of Engineering, University of Calgary, Calgary, Alberta, Canada
JAMA Neurol. 2018;75(12):1477-1486. doi:10.1001/jamaneurol.2018.2424
Key Points

Question  In suspected acute ischemic stroke with large-vessel occlusion, should thrombolysis-capable stroke centers be bypassed in favor of direct transfer to endovascular-capable stroke centers?

Findings  In this theoretical, conditional probability modeling study, the dominant transport strategy depends on the patient’s distance to both centers and treatment speed. If treatment times are slow at the thrombolysis center, bypass should be considered when the centers are 60 minutes or less apart; with greater transport times between centers, bypass is not always favorable.

Meaning  Regional centralization of stroke triage to endovascular therapy centers will increase positive outcomes after ischemic stroke treatment; immediate alteplase treatment followed by transfer to the endovascular center requires fast treatment and is most relevant for longer transport times.

Abstract

Importance  Ischemic stroke with large-vessel occlusion can be treated with alteplase and/or endovascular therapy; however, the administration of each treatment is time sensitive.

Objective  To identify the optimal triage and transport strategy: direct to the endovascular center (mothership) or immediate alteplase treatment followed by transfer to the endovascular center (drip and ship), for all patients with suspected large-vessel occlusion stroke.

Design Setting, and Participants  This was a theoretical, conditional probability modeling study. Existing data from clinical trials of stroke treatment were used for model generation. The study was conducted from February 1, 2017, to March 1, 2018.

Main Outcomes and Measures  The time-dependent efficacy of alteplase and endovascular therapy and the accuracy of large-vessel occlusion screening tools were modeled to estimate the probability of positive outcome (modified Rankin Scale score, 0-1 at 90 days) for both the drip-and-ship and mothership transport strategies. Based from onset to treatment, the strategy that estimates the greatest probability of excellent outcome is determined in several different scenarios.

Results  The patient’s travel time from both thrombolysis and endovascular therapy centers, speed of treatment, and positive predictive value of the screening tool affect whether the drip-and-ship or mothership strategy estimates best outcomes. With optimal treatment times (door-to-needle time: 30 minutes; door-in-door-out time: 50 minutes; door-to-groin-puncture time: 60 minutes [mothership], 30 minutes [drip and ship]), both options estimate similar outcomes when the centers are 60 minutes or less apart. However, with increasing travel time between the 2 centers (90 or 120 minutes), drip and ship is favored if the patient would have to travel past the thrombolysis center to reach the endovascular therapy center or if the patient would arrive outside the alteplase treatment time window in the mothership scenario. Holding other variables constant, if treatment times are slow at the thrombolysis center (door-to-needle time: 60 minutes; door-in-door-out time: 120 minutes), the area where mothership estimates the best outcomes expands, especially when the 2 centers are close together (60 minutes apart or less). The area where mothership estimates the best outcome also expands as the positive predictive value of the screening tool increases.

Conclusions and Relevance  This study suggests that decision making for prehospital transport can be modeled using existing clinical trial data and that these models can be dynamically adapted to changing realities. Based on current median treatment times to realize the full benefit of endovascular therapy on a population level, the study findings suggest that delivery of the treatment should be regionally centralized. The study modeling suggests that transport decision making is context specific and the radius of superiority of the transport strategy changes based on treatment times at both centers, transport times, and the triaging tool used.

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