A stroke occurs when blood flow to a part of the brain is disrupted, leading to rapid brain cell death. Emergency medical services (EMS) personnel are often the first healthcare providers to encounter individuals experiencing a stroke, playing a crucial role in the initial response. Recognizing and treating a stroke is highly time-sensitive, as timely intervention significantly influences patient outcomes.
Understanding Stroke Types
Strokes are broadly categorized into two main types: ischemic and hemorrhagic. An ischemic stroke, the more common type accounting for approximately 85% of all cases, occurs when a blood clot blocks or significantly narrows an artery supplying blood to the brain. This blockage starves brain tissue of oxygen and nutrients.
A hemorrhagic stroke results from a ruptured blood vessel that bleeds into or around the brain. This bleeding not only deprives brain cells of blood flow but also causes pressure to build up within the skull, further damaging brain tissue. Hemorrhagic strokes represent about 15% of all stroke incidents.
The Purpose of Prehospital Identification
EMS attempts to identify stroke types and severity in the prehospital setting to guide immediate patient care decisions. Early identification influences the choice of hospital destination, such as directing patients to a comprehensive stroke center equipped for advanced treatments. This rapid triage enables the quick initiation of appropriate medical protocols upon hospital arrival.
Different stroke types require distinct acute treatments, making early differentiation important. For example, ischemic strokes may be treated with clot-busting medications, while certain severe ischemic strokes can benefit from mechanical clot removal. Hemorrhagic strokes, conversely, necessitate interventions to manage bleeding and pressure.
What Prehospital Tools Aim to Identify
Prehospital stroke severity tools are primarily designed to identify the likelihood of a large vessel occlusion (LVO) ischemic stroke. LVOs involve blockages in major brain arteries, often leading to more severe deficits that can benefit from specialized interventions like mechanical thrombectomy, a procedure to physically remove blood clots.
These tools help EMS providers determine if a patient might be a candidate for such advanced treatments. Scales like the Rapid Arterial Occlusion Evaluation (RACE) scale, the Los Angeles Motor Scale (LAMS), and the Field Assessment Stroke Triage for Emergency Destination (FAST-ED) are examples used to assess for LVO. By indicating stroke severity and potential LVO, these tools enable EMS to prioritize transport to facilities capable of performing time-sensitive procedures.
Limitations of Prehospital Tools
Prehospital stroke tools serve as screening instruments rather than definitive diagnostic tools. They are not capable of definitively differentiating between an ischemic and a hemorrhagic stroke, as this distinction typically requires imaging like a CT scan performed in a hospital setting. The clinical signs of both stroke types can overlap, making a precise prehospital diagnosis challenging.
These tools also cannot reliably rule out “stroke mimics,” which are conditions that present with stroke-like symptoms but are not actual strokes. Examples of stroke mimics include seizures, migraines, or even low blood sugar.
While prehospital scales generally exhibit high sensitivity in detecting a stroke, they often have lower specificity, meaning they can sometimes indicate a stroke when one is not present. This can lead to a significant number of patients, potentially up to 50%, being transported with suspected stroke who are later diagnosed with a mimic.