Getting the Right Patient to the Right Place in the Right Amount of Time—A Role for Both Mobile Stroke Units and Prehospital Clinical Scales

Abstract

Fundamentally, emergency medical services (EMS) specialize in triage, with a goal of getting the right patient to the right place in the right amount of time. This art of triage may bypass the closest facility for the most appropriate facility and, when performed correctly, improves outcomes after trauma, 1 acute myocardial infarction, 2 and out-of-hospital cardiac arrest. 3 Proper EMS triage can be the most cost-effective strategy in developing systems of care and is favored over creation of additional specialty-receiving facilities. 4 More than half of all patients with acute stroke and most patients with severe stroke arrive at the hospital via EMS. 5 Twenty years ago, prehospital stroke identification and triage was simple because treatment decisions were simple: apply a sensitive, objective clinical decision aid, such as the Cincinnati Prehospital Stroke Scale or the Los Angeles Prehospital Stroke Screen, 6 and, if positive, transport the patient to a hospital capable of administering tissue plasminogen activator. As new treatment options have been established (eg, endovascular therapy) 7 and patient selection has expanded, 8,9 prehospital tools must also evolve.Since 2017, the American Heart Association/American Stroke Association Mission: Lifeline Stroke campaign 10 has recommended use of a stroke severity scale to help EMS professionals identify patients who may benefit from bypassing a closer hospital in favor of one offering more advanced capabilities. While several instruments have been developed, 11 prospective validation in prehospital patients with suspected stroke is limited, and there is insufficient evidence to choose one over another. 7,11,12 These tools demonstrate similar performance, with roughly 70% sensitivity and specificity in predicting which patients with suspected stroke may benefit from comprehensive stroke centers (CSCs); naturally, this translates into 30% overtriage and undertriage rates. Based on current treatment trends, a 5% increase in prehospital triage tool sensitivity translates to an approximate 30% relative increase in appropriate triage of patients with severe stroke; in the United States, thousands more patients with acute ischemic stroke due to large-vessel occlusion (LVO) could be treated with endovascular therapy, and half of treated patients are expected to have less disability due to stroke than without treatment. 13 Concurrent with clinical tool development, the first mobile stroke units (MSUs) appeared. 14 The MSUs "flip the script" by bringing the capabilities of an acute stroke-ready hospital to select patients instead of EMS bringing patients to select hospitals. Early accounts demonstrate significantly improved tis-