Stroke Recognition: FAST and BE-FAST for Paramedics

Why Stroke Recognition Matters in Pre-Hospital Care

Stroke is a time-critical emergency. In the UK, approximately 100,000 people suffer a stroke each year, and outcomes are directly linked to how quickly definitive treatment begins. As a paramedic, you are often the first clinician on scene — your ability to rapidly and accurately identify a stroke can be the difference between full recovery and permanent disability or death.

The mantra in stroke care is simple: time is brain. Every minute a large vessel occlusion goes untreated, approximately 1.9 million neurons are lost. Understanding and applying validated stroke recognition tools is therefore not just a clinical skill — it is a life-saving one.

The FAST Tool: Foundation of Stroke Recognition

FAST has been the cornerstone of both public awareness campaigns and clinical pre-hospital assessment in the UK for over a decade. It was developed to provide a quick, easy-to-remember screening tool that could be applied even by members of the public — but it remains equally relevant for clinicians in the field.

Breaking Down FAST

• F — Face: Ask the patient to smile. Is there facial drooping or asymmetry? Unilateral facial droop is a classic sign of an upper motor neurone lesion affecting the contralateral hemisphere.
• A — Arms: Ask the patient to raise both arms and hold them out. Pronator drift or an inability to maintain arm elevation on one side suggests motor weakness consistent with stroke.
• S — Speech: Is the patient's speech slurred (dysarthria), absent, or are they struggling to find words (dysphasia/aphasia)? Note that a patient may appear confused due to receptive aphasia — they cannot understand your instructions, not because they are obtunded.
• T — Time: Note the time of symptom onset, or the last time the patient was known to be well. This is critical for thrombolysis and thrombectomy eligibility windows.

FAST has a reported sensitivity of around 79% for identifying strokes caused by anterior circulation involvement. However, it is known to miss a significant proportion of posterior circulation strokes, which is where BE-FAST becomes essential.

BE-FAST: An Enhanced Approach for Paramedics

BE-FAST builds on the original FAST tool by adding two additional components that specifically capture posterior circulation strokes — events involving the vertebrobasilar system, cerebellum, and brainstem.

The Two Additional Components

• B — Balance: Has the patient had a sudden onset of balance problems, unsteadiness, or ataxia? Cerebellar strokes commonly present with truncal ataxia and a wide-based gait rather than the classic limb weakness seen in anterior circulation events. Patients may describe feeling as though they are being pulled to one side.
• E — Eyes: Ask about sudden visual disturbance. This includes diplopia (double vision), sudden loss of vision in one or both eyes, or visual field defects (homonymous hemianopia). Posterior circulation strokes frequently affect cranial nerves III, IV, and VI, or the occipital cortex, producing these findings.

Studies have shown BE-FAST improves stroke detection sensitivity to approximately 97% when compared to FAST alone, making it a significantly more comprehensive screening tool for pre-hospital use.

Applying BE-FAST in the Pre-Hospital Environment

In practice, applying BE-FAST does not need to add significant time to your assessment. Integrating it into your structured primary and secondary surveys means you can systematically screen for all major stroke presentations without disrupting your clinical workflow.

Key Considerations for Your Assessment

• Establish the last known well time: This is arguably the most important piece of information you can gather. For thrombolysis (tPA), the window is typically up to 4.5 hours; for mechanical thrombectomy, extended windows of up to 24 hours may apply at specialist centres. Accurate documentation of onset time directly influences the receiving team's treatment decisions.
• Use the NIHSS as a severity guide: While you will not perform a full National Institutes of Health Stroke Scale in the field, familiarity with its components helps you communicate severity to the receiving hospital and identify large vessel occlusion (LVO) patterns, which may require direct transfer to a Comprehensive Stroke Centre rather than the nearest emergency department.
• Blood glucose is mandatory: Hypoglycaemia is the most important stroke mimic you will encounter. JRCALC guidelines mandate blood glucose measurement in all patients presenting with neurological symptoms. A BGL below 4.0 mmol/L should be treated before concluding a stroke diagnosis.
• Blood pressure management: Unless hypertension is severely extreme or another indication exists, do not treat hypertension aggressively in suspected stroke. Elevated blood pressure in the acute phase may be a compensatory mechanism to maintain cerebral perfusion pressure around the ischaemic penumbra.

Stroke Mimics: What Else Could It Be?

Not every patient with focal neurological signs is having a stroke. Pre-hospital paramedics must maintain a broad differential, particularly when the presentation is atypical or the history is inconsistent.

Common Stroke Mimics

• Hypoglycaemia — as above, always check BGL
• Todd's paresis — transient focal weakness following an epileptic seizure
• Hemiplegic migraine — focal neurological deficits accompanying a migraine, often with prior history
• Hypertensive encephalopathy — severe hypertension causing neurological symptoms without focal deficit
• Functional neurological disorder — previously termed conversion disorder; may closely mimic stroke
• Brain tumour — particularly if symptoms have been gradually progressive rather than sudden in onset

A sudden onset of maximal deficit at symptom onset remains the hallmark of stroke. Symptoms that are gradual, fluctuating without clear vascular pattern, or associated with other systemic features should prompt consideration of alternative diagnoses.

Pre-Alert and Handover

Once you have identified a likely stroke, early pre-alert to the receiving hospital is essential. Most NHS stroke networks operate hyperacute stroke unit (HASU) pathways, and your pre-alert activates the stroke team to be ready on arrival. Your handover should include the BE-FAST findings, last known well time, current GCS, blood glucose, blood pressure, and any relevant medical or drug history — particularly anticoagulant use, which significantly affects reperfusion therapy eligibility.