3.1 Introduction

According to the 2018 American Heart Association/American Stroke Association (AHA/ASA) statistics, someone in the United States has a stroke roughly every 40 seconds, accounting for one of every 19 deaths annually and ranking fifth in leading causes of death. Although between 2005 and 2015, the age-adjusted stroke death rate decreased 21.7%, and the actual number of deaths declined by 2.3%, it remains a leading cause of serious long-term disability. ¹ While advances have been made in the treatment of stroke, early recognition and presentation for diagnosis and treatment remain a challenge. Often this is accomplished through the activation of emergency medical services (EMS). While treatment upon arrival is often focused on the door-to-treatment time, EMS may improve the onset-to-door time through rapid assessment and stabilization of the patient and transport to an appropriate destination facility.

As the EMS system is frequently the entry point for stroke care, it plays a crucial role in the AHA chain of survival: Detection, Dispatch, Delivery, Door, Data, Decision, Drug, Disposition. From the early recognition of the signs of stroke, EMS must support critical hemodynamic processes (airway, breathing, circulation), make appropriate destination decisions, and alert the receiving facility with accurate and pertinent information to expedite treatment. Given the relatively narrow window of opportunity for treatment with systemic thrombolytics, EMS plays a crucial role in regional stroke systems. ² In fact, there are many sources of delay in presentation of patients and thus ineligibility for acute reperfusion. ³ Factors associated with increased rates of reperfusion therapy include use of 911, EMS transport, severe symptoms, and first time stroke while decreased rates correlate to private transport, prior stroke history, mild symptoms, and rural locations. ^{4 ,​ 5 ,​ 6}

3.2 911 and EMS Dispatch

In order for patient management to begin, EMS must be activated by either the patient or a witness to the event. Through public education initiatives and outreach programs, the recognition of stroke symptoms is emphasized to include alterations in speech, weakness, or mentation. ² Once these symptoms are recognized and 911 is activated, the initial point of contact is the emergency dispatcher or operator. Recognition of stroke as a potential diagnosis by the dispatcher is essential. While tools such as Emergency Medical Dispatch provide great assistance with recognition, there is still significant variability, with correct identification varying between 30 and 83%. ⁷ A well-organized regional stroke system not only educates dispatchers in recognition of stroke symptoms, but enables early notification of the receiving hospitals on impending arrivals, either through dispatch or EMS.

An AHA/ASA policy statement titled Implementation Strategies for Emergency Medical Services Within Stroke Systems of Care has identified the following parameters as measurements of quality from the EMS System (EMSS):

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  Stroke patients are dispatched at the highest level of care available in the shortest time possible

  
  
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  The time between the receipt of the call and the dispatch of the response team is < 90 seconds

  
  
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  EMSS response time is < 8 minutes

  
  
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  Dispatch time is < 1 minute

  
  
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  Turnout time is < 1 minute

  
  
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  The on-scene time is < 15 minutes

  
  
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  Travel time is equivalent to trauma or acute myocardial infarction calls ²

3.3 EMS Assessment

The initial primary survey of a stroke patient by EMS providers has the same priorities as other disease processes: Airway, Breathing, and Circulation. The presence of deficits in head and neck innervation may make secretion management more difficult and increase the risk of aspiration. Additionally, in ischemic strokes, higher blood pressures are tolerated, as they may be required to perfuse the penumbra. However, extreme hypertension (>220 mm Hg systolic) may be treated in consultation with medical control. Respiratory depression is less common, but oxygenation and ventilation can be supported as necessary. Hyperventilation as a therapy should be avoided in the absence of signs of impending brain herniation given the risk of decreased cerebral perfusion. Special attention should be paid to circulatory status and ECG, given the association between cardiac arrhythmias and stroke. Additionally, blood glucose levels are routinely assessed, as hypoglycemia may mimic stroke-like symptoms. Intervention should include, if possible, an intravenous line amenable to the administration of medication as well as contrast material for diagnostic computer tomography (CT). However, none of these additional interventions should take priority over the rapid transport of the patient to an appropriate facility. ²

History gathering may be difficult in a patient with aphasia or dysarthria, and supplemental history from family or witnesses should be gathered whenever possible. Critical history includes the “last known normal” or “last known well” time. This is the most recent point of time that the patient was without current stroke-like symptoms and represents “time zero” for the implementation of time-sensitive interventions such as thrombolytics. The “wake-up stroke” in which the patient awakens with symptoms presents an additional challenge, as the time used must correspond to when the patient was last known to be awake and symptom free, often prior to bed the night before. Additional points of history should include past medical history (e.g., prior stroke, seizure disorder, atrial fibrillation, or diabetes) as well as a medication history with special focus on systemic anticoagulants. ² Concomitantly with these interventions and history points, a validated stroke screening and severity tool should be utilized.

3.4 Assessment Tools

For the detection of stroke symptoms by EMS, the patient should undergo an examination with a validated stroke assessment tool. These tools can be broken down into two broad categories: Screening and Severity tools. A wide variety of these tools exist, with the most common screening tools being the Cincinnati Prehospital Stroke Scale (CPSS) and Los Angeles Prehospital Stroke Scale (LAPSS). These tools include simple assessments for strength, facial droop, and speech, while the LAPSS includes limited historical factors. These tools are used in a binary fashion to detect positive stroke symptoms but were not designed to assess symptom severity. In a systematic review of these scales, it was found that the LAPSS was more consistent but had similar diagnostic capabilities to the CPSS. The accuracy of these tests varies, with up to 30% of strokes being missed. ³

With the latest update of the AHA/ASA guidelines, there is an increased focus on recognition of large vessel occlusions (LVO), as these are more likely to be amenable to endovascular therapy. ⁸ Therefore, there has been an increased focused on the detection of LVO by the implementation of field-based stroke severity tools to ensure transport of these patients to facilities capable of performing endovascular interventions. These tools include the Cincinnati Stroke Triage Assessment Tool (CSTAT), Field Assessment Stroke Triage for Emergency Destination (FAST-ED), Los Angeles Motor Scale (LAMS) and Rapid Arterial Occlusion Evaluation (RACE) scale. These tools are based off the findings of the National Institutes of Health Stroke Scale (NIHSS), but are less detailed, more brief, and more suitable to the prehospital environment. ⁹ The specific test utilized in a given area depends on local preferences and protocols.

(Table 3‑1, Table 3‑2, Table 3‑3, Table 3‑4)