There have been major advances in prehospital evaluation and triage of patients with stroke symptoms in the past few decades. Progress has been made in educating the public about the importance of activating emergency medical services (EMS) as soon as stroke is suspected, prehospital stroke identification, and routing of patients with stroke to designated acute stroke center hospitals. Areas of active investigation in prehospital stroke include in-ambulance therapy (eg, use of neuroprotective agents), mobile stroke units (MSUs) with imaging capabilities, and multitiered routing protocols. The goal of any prehospital system of stroke care is to deliver patients quickly and safely to the most appropriate hospital.
Prehospital care has had to adapt to recent developments in endovascular care of patients with large-vessel occlusion (LVO) ischemic stroke for whom endovascular thrombectomy with standard stroke care has proven efficacy for reducing disability and improving outcomes.1-4 In this light, prehospital care systems have had to reevaluate identification, routing, and treatment protocols for patients with potential LVO. This article reviews the current state of prehospital routing for patients with stroke, the landscape of prehospital recognition and triage of with LVO, and future directions for routing patients experiencing a stroke and addresses the question of what is the best system of stroke triage: transport to the closest primary stroke center (PSC), thrombectomy-capable stroke center (TCS), or comprehensive stroke center (CSC).
Current Prehospital Evaluation for Stroke
About half of patients experiencing stroke arrive to the emergency department (ED) by ambulance, putting emergency medical service (EMS) providers in a unique position as the first medical professionals to evaluate a patient with stroke. Recognizing a potential stroke patient begins with EMS dispatch operators who field emergency calls (usually via 911 services in the US).5 Stroke identification by dispatch operators has low sensitivity and high specificity. This is because not all callers are able to correctly identify symptoms and signs of stroke and relay them on the phone. Dispatcher identification of potential stroke leads to activation of an appropriate EMS team, usually via an advanced life-support ambulance.
Most paramedics and emergency medical technicians (EMTs) are trained to use validated prehospital stroke recognition tools, most commonly the Face Arm Speech Test (FAST)/Cincinnati Prehospital Stroke Scale (CPSS). Other validated screening tools include the Los Angeles Prehospital Stroke Screen (LAPSS), Recognition of Stroke in the Emergency Room (ROSIER), Melbourne Ambulance Stroke Scale (MASS), Ontario Prehospital Stroke Screening tool (OPSS), and Medic Prehospital Assessment for Code Stroke (MedPACS). The CPSS/FAST has 3 components—unilateral facial weakness, unilateral arm weakness, and speech abnormality—and the highest level of sensitivity. More complex instruments such as LAPSS have higher specificity at the cost of lower detection rates.6 None of the stroke screening instruments is particularly good at picking up posterior circulation symptoms.
When a stroke diagnosis is not made in the field, it can still be made in the ED where the regional stroke system can be accessed. All prehospital stroke-triage protocols incorporate paramedic-determined last known well time (LKWT) and incorporate transport times into their routing algorithms. For example, routing to a stroke center may not be feasible if transport time would be over 1 hour. Regional routing protocols vary widely in characteristics, including screening instrument, symptom onset time, destination facility features, and transport times.7 Each regional stroke system has to be tailored to local geographic resources.
The practice of routing patients with stroke to a designated hospital rather than the closest hospital has been expanding, leading to meaningful differences in the proportion of patients with stroke who are cared for at certified stroke centers.8,9 In Los Angeles, implementation of stroke-specific routing increased the proportion of patients with stroke being seen at certified centers from 1 in 10 to more than 9 in 10, with no clinically significant increase in prehospital care time.10 This expansion of EMS care systems has been in parallel to increased numbers of hospitals seeking stroke center certification nationwide.11 Currently, more than 1 in 3 acute care hospitals are certified in some manner as a stroke center.12
A multitiered stroke center certification was developed as it was recognized that increasing specialization leads to better outcomes in stroke (Table). With so many stroke certification tiers, there is often confusion on how to approach prehospital triage, and this is an ongoing area of research. There is agreement on the importance of rapid transport to minimize delay. Paramedics gather information key to stroke evaluation including LKWT and current medications prior to transport. Vital signs are monitored during transport and there is prenotification to the receiving hospital in most cases. These are outlined in the American Heart Association (AHA)/American Stroke Association (ASA) policies to guide systems of stroke care delivery.13
Challenges for Prehospital Care
Identifying and Routing Patients With Large Vessel Occlusion
Identifying patients with LVO in the field is the first step to improving outcomes. The first generation of stroke screening tools was developed for stroke recognition with no focus on LVO. There have since been many attempts to develop a prehospital instrument to identify patients with LVO, including the Los Angeles Motor Scale (LAMS),14 Prehospital Acute Stroke Severity (PASS) scale,15 CPSS,16 and the Rapid Arterial oCclusion Evaluation (RACE) scale.17 All are designed to be brief and easy to administer by paramedics; none has emerged as a consensus leader. Identification of patients with LVO in the field is intended to help in routing patients past a nonendovascular stroke center (acute stroke ready [ASR] or PSC) to an endovascular-capable center (TCS or CSC) (Table), which creates the opportunity to consider regional routing systems with only 2 tiers (Figure 1).
The effect of 2-tiered routing and comparison of this method to a single-tiered method is unknown at this time. The RACECATa clinical trial is testing the hypothesis that bypass of the closest stroke center and direct transport to the closest TCS will improve outcomes in paramedic-evaluated patients with stroke.
There are 3 approaches to patients with suspected stroke who are eligible to be treated with tissue plasminogen activator (tPA) (Figure 2). In the first option, which can be thought of as “drip-and-ship,” the patient is transported to the closest stroke center, regardless of tier, for earlier intravenous tPA and in-hospital screening for LVO followed by secondary ambulance transport to an endovascular center if that is indicated. In the second approach, the patient is transported directly to a TCS, bypassing closer stroke centers that are not thrombectomy-capable. Although this could delay tPA administration because of a longer transport time, it might shorten overall time to thrombectomy because the patient would be taken directly to a “mothership” with all aspects of stroke care—tPA, thrombectomy, and poststroke critical care—in an all-in-one location. A third approach is the MSU, where tPA can be administered and imaging can be done as the patient is being transported to the appropriate stroke center.
Figure 2. Approaches to consider for stroke care systems. In the drip-and-ship model (A), a patient is brought to a tPA-capable hospital for imaging and tPA administration and then may be moved to a thrombectomy-ready hospital. In the mothership model, the patient is brought to a hospital for imaging, tPA, and thrombectomy in the same center. In the mobile stroke unit (MSU) model, an ambulance with teleradiology determines if tPA is indicated, and ambulance personnel may administer tPA and then bring the patient to the appropriate hospital depending on whether or not thrombectomy is indicated.
Each of these approaches will have different challenges that are specific to the system and region. The centralized or mothership system does come at a significant burden to any ambulance system because prehospital personnel would participate in longer transports to less familiar parts of town. Taking ambulances out of a local region to transport patients to higher-tier care centers makes fewer ambulances available to respond to other calls. Some regions are further challenged by variable traffic patterns and long transport times in between hospitals. Defining the maximum transport time acceptable for bypassing to the thrombectomy-capable and comprehensive centers is vital. Although the AHA has recommended a 20-minute transport time, each region will have to determine their maximum transport times based on regional characteristics.
An area of active investigation in the BEST-MSUb trial, MSUs may reduce time to thrombolysis with tPA for patients with ischemic stroke. Costs of maintaining an MSU are high, however, and methods to optimize response to patients with LVO still need to be developed. Identification of LVO in the field by MSUs may have a role in the development of regional stroke systems, if it is shown to be effective and not cost prohibitive.
Communication and Coordination of Care
Relationships between different types of stroke centers (ie, ASRs, PSCs, TSCs, and CSCs) are vital to any of the approaches described. All prehospital stroke-screening instruments will miss some patients with LVO who can be identified in the ED and these patients will need to be appropriately screened for tPA administrations and then transported as needed for thrombectomy. Because up to half of patients with stroke present to the ED though a non-EMS pathway, the importance of regional care systems and communication between nonstroke-center hospitals and regional stroke centers for help in diagnosis, treatment, and triage cannot be understated.
Overtriage and Undertriage
Current prehospital LVO triage scales may delay administration of tPA in patients without LVO. Treatment of acute ischemic stroke (AIS) with tPA18 is highly time dependent, and every 15-minute delay in administering tPA reduces the chance of functional recovery and increases mortality and symptomatic intracerebral hemorrhage (ICH).19,20 If a false-positive prehospital LVO-stroke triage assessment (over-triage) leads EMS to extend transport times by bypassing an intravenous (IV) tPA-capable hospital in favor of a more distant stroke center with a higher level of care (the mothership model), the delay in tPA administration could contribute to worse outcomes. Such over-triage may decrease efficiency of nonthrombectomy hospitals because of reduced volume and experience,21 whereas more specialized centers may become crowded with patients who don’t require that level of care, which could reduce capacity of that center to accept transfers of complex cases as a result of increased volume.22
Stopping for tPA at a nonthrombectomy hospital (the drip-and-ship model) delays endovascular thrombectomy. Endovascular thrombectomy1,23-26 is also highly time-dependent, and a false-negative assessment using a prehospital LVO tool (under-triage) may route a patient with AIS-LVO to a hospital without thrombectomy capabilities. Secondary transfer after tPA administration to a thrombectomy-enabled care center can delay thrombectomy by 95 to 109 minutes.26,27 Despite rigorous process-improvement initiatives, transfer delays of more than an hour are common.28 Every 4-minute delay of thrombectomy increases the degree of 90-day disability (modified Rankin Scale [mRS] shift) for 1 of 100 treated patients and every hour in delay to thrombectomy increases morbidity.29 Mistriage is associated with an absolute 8% decrease in freedom from disability and an absolute 9% decrease in functional independence.27
Modern EMSs exist to identify and stabilize patients with time-dependent emergencies while ensuring the right patient gets to the right hospital 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,30 acute myocardial infarction,31,32 and out-of-hospital cardiac arrest.33 Proper EMS triage can be the most cost-effective strategy in developing care systems and is favored over creation of more specialty receiving facilities.34 Under-triage, or taking a patient to a lower level of care than optimal, introduces delays from subsequently needed secondary transfer. Emergent definitive neurosurgical care with ventriculostomy, decompressive craniectomy, or aneurysmal clipping or coiling for ICH35,36 and subarachnoid hemorrhage (SAH),37-40 is unnecessarily delayed.
Almost all published research related to existing EMS stroke-screening tools focuses on identifying patients with LVO; this conflicts with the purpose of triage itself—getting the right patient to the right place in the right amount of time—regardless of diagnosis. A patient with a positive prehospital severity score and a large ICH, which requires immediate surgical decompression, may be considered a false positive even though the tool resulted in appropriate routing to the appropriate care center in these studies because the patient did not have an LVO. Similarly, a patient with a low probability of LVO on a stroke-screening tool and a distal arterial occlusion might be considered a false negative, even though they would not have qualified for thrombectomy based on current guidelines4 and could be cared for at the PSC.
Summary and Future Directions
Important advances in AIS treatment have been achieved, including demonstration of benefit from prehospital care systems,41 care delivery on stroke units,42 reperfusion therapy with tPA,18 and reperfusion therapy with endovascular thrombectomy1; however, there are still limitations and challenges to address.
Intravenous tPA can only be administered after neuroimaging has ruled out ICH,43-45 and although the benefits are strongly time-dependent, in current clinical practice in the US, tPA is not started until an average of 2 hours and 20 minutes after onset, well after the accumulation of substantial irreversible injury in most patients.46 Endovascular therapy is indicated in only 3% to10% of patients with AIS, and these patients have to be transported to a tertiary neuroendovascular center. Although the benefit of endovascular therapy is also strongly time-dependent,24,25 reperfusion is currently not achieved until a median of 4 hours and 45 minutes from onset.1 Because substantial brain injury accrues before reperfusion can be achieved, even among patients with AIS treated with endovascular therapy, 73% of patients have outcomes of disability or death.1
Improvements in the care systems to deliver appropriate patients to endovascular-capable hospitals are needed. An ideal stroke care system would reliably identify the presence of LVO among patients evaluated in the field and route them urgently to the most appropriate facility. Regional cooperation would lead to maximization of resources by concentrating endovascular care in the most geographically appropriate locations. This care system will need to include nonendovascular PSCs for rapid tPA administration, endovascular PSCs for rapid endovascular treatment without the ability to manage the most complicated cases, and CSCs providing round-the-clock care (24 hours/day, 7 days/week) for the most complex patients. Centralization of the triage process in the local EMS agency and cooperation and data sharing among all stakeholders will also be essential.
There is no easy answer to the question of primary, comprehensive, or thrombectomy-capable. The question will be different for every individual patient and every stroke care system. It is only by coordination between emergency medical providers, stroke care systems, neurologists, radiologists, and neurosurgeons that we can maximize the potential of prehospital stroke care and improve outcomes for patients with stroke.
a. Direct transfer to an endovascular center compared to transfer to the closest stroke center in acute stroke patients with suspected large vessel occlusion (NCT02795962).
b. Benefits of stroke treatment delivered using a mobile stroke unit (NCT02190500).
1. Goyal M, Menon BK, Van Zwam WH, et al. Endovascular thrombectomy after large-vessel ischaemic stroke:a meta-analysis of individual patient data from five randomised trials. Lancet. 2016 ;387(10029):1723-1731.
2. Saver J, Levy E, McDougall C, et al. Planning for nationwide endovascular acute ischemic stroke care in the united states: report of the interventional stroke workforce study group. The Stroke Interventionalist. 2012;1(1). https://escholarship.org/uc/item/585048hm. Accessed December 10, 2018.
3. Zaidat OO, Lazzaro M, McGinley E, et al. Demand-supply of neurointerventionalists for endovascular ischemic stroke therapy. Neurology. 2012;79(13 Suppl 1):S35-S41.
4. Powers WJ, Derdeyn CP, Biller J, et al. 2015 AHA/ASA focused update of the 2013 guidelines for the early management of patients with acute ischemic stroke regarding endovascular treatment: a guideline for healthcare professionals from the American Heart Association/American Stroke Association. Stroke. 2015;46(10):3020-3035.
5. Buck BH, Starkman S, Eckstein M, et al. Dispatcher recognition of stroke using the national academy medical priority dispatch system. Stroke. 2009;40:2027-2030.
6. Rudd M, Buck D, Ford GA, Price CI. A systematic review of stroke recognition instruments in hospital and prehospital settings. Emerg Med J. 2016;33(11):818-822.
7. Dimitrov N, Koenig W, Bosson N, et al. Variability in criteria for emergency medical services routing of acute stroke patients to designated stroke center hospitals. West J Emerg Med. 2015;16:743-746.
8. Hanks N, Wen G, He S, et al. Expansion of US emergency medical service routing for stroke care: 2000-2010. West J Emerg Med. 2014;15:499-503.
9. Song S, Saver J. Growth of regional acute stroke systems of care in the united states in the first decade of the 21st century. Stroke. 2012;43:1975-1978.
10. Sanossian N, Liebeskind DS, Eckstein M, et al. Routing ambulances to designated centers increases access to stroke center care and enrollment in prehospital research. Stroke. 2015;46:2886-2890.
11. Schuberg S, Song S, Saver JL, et al. Impact of emergency medical services stroke routing protocols on primary stroke center certification in California. Stroke. 2013;44:3584-3586.
12. Ramirez L, Krug A, Nhoung H, et al. Vascular neurologists as directors of stroke centers in the United States. Stroke. 2015;46:2654-2656.
13. Higashida R, Alberts MJ, Alexander DN, et al. Interactions within stroke systems of care: a policy statement from the American Heart Association/American Stroke Association. Stroke. 2013;44:2961-2984.
14. Llanes JN, Kidwell CS, Starkman S, et al. The Los Angeles Motor Scale (LAMS): a new measure to characterize stroke severity in the field. Prehosp Emerg Care. 2004;8:46-50.
15. Hastrup S, Damgaard D, Johnsen SP, Andersen G. Prehospital acute stroke severity scale to predict large artery occlusion: design and comparison with other scales. Stroke. 2016;47:1772-1776.
16. Katz BS, McMullan JT, Sucharew H, Adeoye O, Broderick JP. Design and validation of a prehospital scale to predict stroke severity: Cincinnati Prehospital Stroke Severity Scale. Stroke. 2015;46:1508-1512.
17. Perez de la Ossa N, Carrera D, Gorchs M, et al. Design and validation of a prehospital stroke scale to predict large arterial occlusion: the rapid arterial occlusion evaluation scale. Stroke. 2014;45:87-91.
18. Emberson J, Lees KR, Lyden P, et al. Effect of treatment delay, age, and stroke severity on the effects of intravenous thrombolysis with alteplase for acute ischaemic stroke: a meta-analysis of individual patient data from randomised trials. Lancet. 2014;384(9958)1929-1935.
19. Saver JL, Fonarow GC, Smith EE, et al. Time to treatment with intravenous tissue plasminogen activator and outcome from acute ischemic stroke. JAMA. 2013;309(23):2480-2488.
20. Kim JT, Fonarow GC, Smith EE, et al. Treatment with tissue plasminogen activator in the golden hour and the shape of the 4.5-hour time-benefit curve in the national United Sstates get with the guidelines-stroke population. Circulation. 2017;135:128-139.
21. Saposnik G, Baibergenova A, O’Donnell M, Hill MD, Kapral MK, Hachinski V, et al. Hospital volume and stroke outcome: does it matter? Neurology. 2007;69:1142-1151.
22. Katz BS, Adeoye O, Sucharew H, et al. Estimated impact of emergency medical service triage of stroke patients on comprehensive stroke centers: an urban population-based study. Stroke. 2017;48:2164-2170.
23. Goyal M, Menon BK, van Zwam WH, et al. Endovascular thrombectomy after large-vessel ischaemic stroke: a meta-analysis of individual patient data from five randomised trials. Lancet. 2016;387:1723-1731.
24. Mazighi M, Chaudhry SA, Ribo M, et al. Impact of onset-to-reperfusion time on stroke mortality: a collaborative pooled analysis. Circulation. 2013;127:1980-1985.
25. Sheth SA, Jahan R, Gralla J, et al. Time to endovascular reperfusion and degree of disability in acute stroke. Ann Neurol. 2015;78:584-593.
26. Goyal M, Jadhav AP, Bonafe A, et al. Analysis of workflow and time to treatment and the effects on outcome in endovascular treatment of acute ischemic stroke: results from the swift prime randomized controlled trial. Radiology. 2016;279:888-897.
27. Froehler MT, Saver JL, Zaidat OO, et al. Interhospital transfer before thrombectomy is associated with delayed treatment and worse outcome in the STRATIS registry (Systematic Evaluation of Patients Treated With Neurothrombectomy Devices for Acute Ischemic Stroke). Circulation. 2017;136:2311-2321.
28. Kodankandath TV, Wright P, Power PM, et al. Improving transfer times for acute ischemic stroke patients to a comprehensive stroke center. J Stroke Cerebrovasc Dis. 2017;26:192-195.
29. Saver JL, Goyal M, van der Lugt A, et al. Time to treatment with endovascular thrombectomy and outcomes from ischemic stroke: a meta-analysis. JAMA. 2016;316:1279-1288.
30. Martinez B, Owings JT, Hector C, et al. Association between compliance with triage directions from an organized state trauma system and trauma outcomes. J Am Coll Surg. 2017;225:508-515.
31. Lassen JF, Botker HE, Terkelsen CJ. Timely and optimal treatment of patients with stemi. Nat Rev Cardiol. 2013;10:41-48.
32. Chen J, Krumholz HM, Wang Y, et al. Differences in patient survival after acute myocardial infarction by hospital capability of performing percutaneous coronary intervention:implications for regionalization. Arch Intern Med. 2010;170:433-439.
33. Cournoyer A, Notebaert E, de Montigny L, et al. Impact of the direct transfer to percutaneous coronary intervention-capable hospitals on survival to hospital discharge for patients with out-of-hospital cardiac arrest. Resuscitation. 2018;125:28-33.
34. Concannon TW, Kent DM, Normand SL, et al. Comparative effectiveness of st-segment-elevation myocardial infarction regionalization strategies. Circ Cardiovasc Qual Outcomes. 2010;3:506-513.
35. Kuramatsu JB, Gerner ST, Schellinger PD, et al. Anticoagulant reversal, blood pressure levels, and anticoagulant resumption in patients with anticoagulation-related intracerebral hemorrhage. JAMA. 2015;313:824-836.
36. Hemphill JC 3rd, Greenberg SM, Anderson CS, et al. Guidelines for the management of spontaneous intracerebral hemorrhage: a guideline for healthcare professionals from the American Heart Association/American Stroke Association. Stroke. 2015;46:2032-2060.
37. Phillips TJ, Dowling RJ, Yan B, Laidlaw JD, Mitchell PJ. Does treatment of ruptured intracranial aneurysms within 24 hours improve clinical outcome? Stroke. 2011;42:1936-1945.
38. Beynon C, Nofal M, Rizos T, Laible M, Potzy A, Unterberg AW, et al. Anticoagulation reversal with prothrombin complex concentrate in aneurysmal subarachnoid hemorrhage. J Emerg Med. 2015;49:778-784.
39. Connolly ES Jr, Rabinstein AA, Carhuapoma JR, et al. Guidelines for the management of aneurysmal subarachnoid hemorrhage: a guideline for healthcare professionals from the American Heart Association/American Stroke Association. Stroke. 2012;43:1711-1737.
40. Lawton MT, Vates GE. Subarachnoid hemorrhage. N Engl J Med. 2017;377:257-266.
41. Schwamm LH, Pancioli A, Acker JE, 3rd, et al. Recommendations for the establishment of stroke systems of care: recommendations from the American Stroke Association’s task force on the development of stroke systems. Stroke. 2005;36:690-703.
42. Stroke Unit Trialists C. Organised inpatient (stroke unit) care for stroke. Cochrane Database Syst Rev. 2013;9:CD000197.
43. Adeoye O, Hornung R, Khatri P, Kleindorfer D. Recombinant tissue-type plasminogen activator use for ischemic stroke in the United States: a doubling of treatment rates over the course of 5 years. Stroke. 2011;42:1952-1955.
44. von Kummer R, Broderick JP, Campbell BC, et al. The heidelberg bleeding classification: classification of bleeding events after ischemic stroke and reperfusion therapy. Stroke. 2015;46:2981-2986.
45. Jauch EC, Saver JL, Adams HP, Jr., et al. Guidelines for the early management of patients with acute ischemic stroke: a guideline for healthcare professionals from the American Heart Association/American Stroke Association. Stroke. 2013;44:870-947.
46. Saver Jl, Fonarow GC, Smith EE, et al. Time to treatment with intravenous tissue plasminogen activator and outcome from acute ischemic stroke. JAMA. 2013;309:2480-2488.
NS serves as a member of the speaker’s bureau for Genentech and a consultant for Medtronic.