Large Vessel Occlusion Identification Through Prehospital Administration of Stroke Scales: A County-wide Emergency Medical Services Prospective Research Protocol.

Abstract

There is yet insufficient research on prehospital stroke scales, especially for identifying large vessel occlusions and severe strokes. When multiple stroke centers are available, determining which patients should go directly to a comprehensive stroke center (CSC) is critical. Delay in care transporting to a hospital not capable of treating hemorrhagic strokes and large vessel occlusions (LVOs) can be devastating. The failure rate for tissue plasminogen activator (tPA), a clot-busting drug commonly used to treat ischemic stroke that can be administered at primary stroke centers, is up to 90% for large vessel occlusions (LVOs). However, these patients can benefit from mechanical intervention, performed only at CSCs. Hemorrhagic strokes often result from ruptured aneurysms, which can benefit from coiling and clipping, procedures also typically only available at CSCs.In order to analyze the effectiveness of certain prehospital stroke scales, our county’s emergency medical services (EMS) system designed and implemented the LVO identification through prehospital administration of stroke scales (LIT-PASS), a prospective cohort study. Our study has three phases, each phase testing a certain combination of prehospital stroke scales. The protocol, including training for every paramedic, was started in 2015, and data collection began in 2016. In Phase 1, we tested the Los Angeles motor scale (LAMS) alone from January 2016 to November 2018. In Phase 2, we administered both the LAMS and the vision, aphasia, neglect (VAN) test from December 2018 to May 2019. Phase 3 began in June 2019 and uses the balance, eyes, face, arm, speech, terrible headache/time to call 911 (BE-FAST) test as a scale, allotting one point for each category. While the “time to call 911” aspect is not part of the scale, it is included in the name for mnemonic reasons. We chose these scales because of the symptoms they cover and due to their simplicity. Phase 1 assesses only motor symptoms, Phase 2 assesses motor and additional cortical symptoms, and Phase 3 evaluates a scale that combines both components and whose acronym is a useful mnemonic for paramedics.Each paramedic in our county’s system was given a one-hour training session on the scales each year in Phase 1 and once prior to the beginning of Phase 2 and Phase 3. Paramedics were not allowed to respond to a stroke call unless they had completed the training. This is done to avoid bias in which patients are studied, ensuring that all stroke patients are subject to our county's stroke protocol. Data were de-identified and analyzed to evaluate the effectiveness of four things: in Phases 1 and 2, the LAMS alone; in Phase 2, the VAN test alone, as well as in combination with the LAMS; and in Phase 3, the effectiveness of the BE-FAST scale.