As endovascular treatments provide greater clinical benefit for LVO strokes, it will become more important for EMS clinicians to be able to risk stratify and transport these patients to larger centers. Among prehospital stroke scores, none are perfect in predicting LVO strokes. In a study of 138 patients, a CPSS (Table 18.1) equal to 3 reliably predicted an LVO (OR 5.7, 95% CI 2.3‐14.1). Among patients with a CPSS = 3, 72.7% had an LVO, compared with 34.3% of patients with CPSS ≤2 (p < 0.0001) [27]. In another study of 440 patients, the Rapid Arterial oCclusion Evaluation (RACE) scale was found to have acceptable discrimination with a RACE score ≥5 having a sensitivity of 66% and specificity of 72% (positive predictive value [PPV] 47%, negative predictive value 86%) (Table 18.3). However, sensitivity and PPV were lower than in the original validation study, and further work is needed to determine the optimal prehospital screening tool for identification of LVO [28].
Table 18.3 Rapid Arterial Occlusion Evaluation (RACE) Scale
Source: Perez de la Ossa N, Carrera D, Gorchs M, et al. Design and validation of a prehospital stroke scale to predict large arterial occlusion. Stroke. 2014; 45:87–91. Used with Permission of Wolters Kluwer.
| Item | RACE score | NIHSS score equivalence |
|---|---|---|
| Facial palsy | ||
| Absent | 0 | 0 |
| Mild | 1 | 1 |
| Moderate to severe | 2 | 2–3 |
| Arm motor function | ||
| Normal to mild | 0 | 0–1 |
| Moderate | 1 | 2 |
| Severe | 2 | 3–4 |
| Leg motor function | ||
| Normal to mild | 0 | 0–1 |
| Moderate | 1 | 2 |
| Severe | 2 | 3–4 |
| Head and gaze deviation | ||
| Absent | 0 | 0 |
| Present | 1 | 1–2 |
| Aphasia* (if right hemiparesis) | ||
| Performs both tasks correctly | 0 | 0 |
| Performs 1 task correctly | 1 | 1 |
| Performs neither tasks | 2 | 2 |
| Agnosia† (if left hemiparesis) | ||
| Patient recognizes his/her arm and the impairment | 0 | 0 |
| Does not recognized his/her arm or the impairment | 1 | 1 |
| Does not recognize his/her arm nor the impairment | 2 | 2 |
| Score total | 0–9 |
Box 18.3 Time interval goals for fibrinolytic therapy
Arrival via EMS at the closest ED capable of delivering fibrinolytic as soon as safely possible
EMS should provide notification while en route to receiving hospital for suspected stroke patients
Rapid assessment by stroke team or emergency physician
Completion of computed tomography (CT) scan within 20 minutes
Administration of fibrinolytic (tPA) within 60 minutes of arrival to ED and within 4.5 hours of symptom onset for eligible patients
Source: Modified from Powers WJ, Rabinstein AA, Ackerson T, et al. 2018 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. 2018; 49:e46–e99.
All of these treatments for stroke have potentially devastating complications, the most noteworthy being intracranial bleeding. In addition, these interventions have several exclusion criteria that must be considered when selecting patients, but are beyond the scope of this chapter. Nonetheless, it is important that EMS clinicians have at least a general understanding of available stroke treatments, as well as the rationale for accurate and rapid identification of the stroke victim. Box 18.3 describes the current AHA/ASA time‐to‐treatment goals related to IV tPA. Ideally, the time window from ED arrival to drug administration should not exceed 60 minutes [9].
EMS transport
Given the narrow time windows of opportunity associated with the various interventional stroke therapies and the clearly demonstrated benefit of earlier treatment, EMS is a critical link to ensuring that patients arrive at facilities capable of treating strokes in an expedited manner. Numerous studies have shown that stroke patients accessing the EMS system have a significantly greater chance of timely arrival at an emergency department, which in turn, can promote higher thrombolytic treatment rates [29–32]. More specifically, the California Acute Stroke Prototype Registry (CASPR) collected data from several California hospitals to identify factors that resulted in delayed presentation for treatment. This study indicated that if patients experiencing stroke symptoms (that