5.1 Protocol 28: Stroke / CVA & Prehospital Stroke Screening

5.1 Protocol 28: Stroke / CVA & Prehospital Stroke Screening

Quick Answer: Protocol 28 governs dispatch triage for suspected Cerebrovascular Accidents (CVA) and Transient Ischemic Attacks (TIA). Stroke is an ultra-time-sensitive medical emergency where "Time is Brain"—an estimated 1.9 million neurons die every minute during untreated ischemic infarction. Emergency Medical Dispatchers (EMDs) must immediately establish the Last Known Well (LKW) timestamp to determine candidate eligibility for intravenous thrombolysis (alteplase/tenecteplase within 3 to 4.5 hours) and endovascular thrombectomy (EVT up to 24 hours for Large Vessel Occlusions). The EMD administers the scripted Stroke Diagnostic Tool (assessing facial droop, arm drift, and speech abnormalities), alerts receiving stroke centers, elevates the patient's head 15 to 30 degrees, and strictly enforces NPO status (no food, water, or medication).

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Pathophysiology: Ischemic vs. Hemorrhagic Stroke

A cerebrovascular accident occurs when cerebral blood flow is abruptly interrupted, depriving neural tissue of oxygen and glucose. Stroke is fundamentally divided into two major pathophysiologic variants with radically different clinical trajectories and management strategies:

1. Ischemic Stroke (~87% of all CVAs)

Ischemic stroke occurs when an intracranial artery is occluded by either a local thrombus or an upstream thromboembolism (commonly originating from atrial fibrillation, carotid artery plaques, or deep cardiac chambers):

• Ischemic Core: The central zone of brain tissue where perfusion drops below critical thresholds (<10 mL/100g/min), causing rapid cellular depolarization, irreversible membrane breakdown, and cell necrosis within minutes.
• Ischemic Penumbra: The hypoperfused zone surrounding the core where collateral blood flow maintains marginal cellular viability. Without swift reperfusion, penumbral tissue rapidly progresses to permanent infarction. Prehospital and dispatch speed aims entirely at salvaging this penumbra.

2. Hemorrhagic Stroke (~13% of all CVAs)

Hemorrhagic stroke results from the rupture of a cerebral blood vessel, exposing brain parenchyma to extravasated blood and abrupt elevations in intracranial pressure (ICP):

• Intracerebral Hemorrhage (ICH, ~10%): Caused primarily by chronic systemic hypertension leading to rupture of microaneurysms in penetrating deep vessels (e.g., basal ganglia, thalamus, pons, cerebellum). Blood forms an expanding hematoma that compresses adjacent parenchyma, triggers mass effect, herniation, and severe midline shift.
• Subarachnoid Hemorrhage (SAH, ~3%): Rupture of an intracranial aneurysm (saccular/berry aneurysm) or arteriovenous malformation (AVM) into the subarachnoid space. Classic hallmark is the catastrophic "thunderclap headache"—frequently described by callers as "the worst headache of my life"—often accompanied by neck stiffness, photophobia, rapid syncope, or seizure.

+-------------------------------------------------------------------------+
|                     STROKE PATHOPHYSIOLOGY AT DISPATCH                  |
|                                                                         |
|   Ischemic (87%):    Arterial clot -> Penumbra tissue dying -> Reperfusion|
|   Hemorrhagic (13%): Ruptured vessel -> Hematoma + ICP spike -> Neuro Sx|
|   Cellular Rate:     1.9 million neurons / 14 billion synapses lost/min |
+-------------------------------------------------------------------------+

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The Time-Sensitive "Last Known Well" (LKW) Window

In prehospital stroke care, the definitive metric is Last Known Well (LKW)—the exact timestamp the patient was last witnessed by family, friends, or coworkers to be at their completely normal neurological baseline.

Clinical Distinction: LKW vs. Symptom Discovery Time

Lay callers frequently report the time they noticed the deficit rather than the LKW. The EMD must explicitly interrogate the precise timeline:

• If a patient goes to bed normal at 22:00 and awakens at 06:30 with right-sided hemiplegia, the LKW is 22:00, NOT 06:30. This scenario is classified as a "Wake-up Stroke."
• If a patient was chatting normally at lunch at 12:15, stepped away, and was found slurring words at 12:45, the LKW is 12:15.

Reperfusion Therapeutic Windows

Modern acute stroke networks operate on rigid therapeutic timelines based on the LKW:

1. Intravenous Thrombolytic Therapy (IVT): Intravenous recombinant tissue plasminogen activator (rtPA, alteplase) or tenecteplase (TNK). Standard therapeutic window is 0 to 3 hours from LKW, extended up to 4.5 hours in selected candidates without contraindications (such as recent surgery, active bleeding, severe coagulopathy, or intracranial hemorrhage on CT).
2. Endovascular Thrombectomy (EVT): Catheter-based mechanical extraction of large clots using stent retrievers and aspiration catheters. Standard window is 0 to 6 hours for anterior circulation Large Vessel Occlusions (LVOs). Landmark clinical trials (DAWN and DEFUSE-3) demonstrated therapeutic benefit up to 24 hours from LKW when advanced perfusion neuroimaging (CT perfusion or MRI diffusion-weighted imaging) identifies salvageable penumbral tissue.

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The MPDS Prehospital Stroke Diagnostic Tool

The MPDS integrates a validated prehospital screening mechanism derived from the Cincinnati Prehospital Stroke Scale (CPSS). When Case Entry identifies stroke, paralysis, numbness, or facial droop, the EMD activates the interactive Stroke Diagnostic Tool during Key Questions:

                          MPDS STROKE DIAGNOSTIC TOOL
                                      |
        +-----------------------------+-----------------------------+
        |                             |                             |
   1. SMILE / FACE              2. ARMS (10 sec)              3. SPEECH
"Smile or show teeth"       "Eyes closed, palms up"      "Repeat simple phrase"
        |                             |                             |
  [ ] Symmetrical               [ ] Both stay up             [ ] Normal / Clear
  [ ] Droops / Unequal          [ ] One drifts down          [ ] Slurred / Inappropriate
        |                             |                             |
        +-----------------------------+-----------------------------+
                                      |
                     ANY SINGLE DEFICIT = POSITIVE SCREEN
                      (> 72% Probability of Acute CVA)

Diagnostic Administration Instructions

1. Facial Droop Test: "Ask him/her to smile or show their teeth."
   • Normal: Both sides of the face move equally and symmetrically.
   • Abnormal: One side of the face does not move, or droops visibly compared to the other.
2. Arm Drift Test: "Ask him/her to close both eyes and hold both arms straight out in front of them with palms facing up for 10 seconds."
   • Normal: Both arms remain elevated equally, or move down simultaneously and symmetrically.
   • Abnormal: One arm drifts downward, falls completely, or cannot be raised at all.
3. Speech Abnormality Test: "Ask him/her to repeat a simple sentence like: 'You can't teach an old dog new tricks' (or 'The grass is green')."
   • Normal: The patient uses correct words with crisp, clear articulation.
   • Abnormal: The patient slurs words, uses inappropriate words, speaks incomprehensibly, or cannot speak or understand speech at all (aphasia).

Diagnostic Probability and Triage Impact

• Single Abnormal Finding: A deficit in any one of the three components confers a 72% probability of an acute ischemic or hemorrhagic stroke.
• All Three Abnormal Findings: When all three components are positive, the probability exceeds 85%.
• If the caller is unable to perform the physical test (e.g., patient is non-cooperative, confused, or third-party call), the EMD codes based on reported history while documenting uncompleted tests.

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Large Vessel Occlusion (LVO) Indicators

A Large Vessel Occlusion (LVO) represents the most devastating form of acute ischemic stroke, accounting for over 60% of stroke-related post-stroke dependence and 90% of stroke mortality. LVO involves acute occlusion of a major proximal cerebral trunk, such as:

• Internal Carotid Artery (ICA)
• Middle Cerebral Artery (MCA, M1 or proximal M2 segments)
• Basilar Artery (posterior circulation, conferring high mortality)

Key Clinical Features of LVO at Dispatch

Dispatchers and EMS field screening algorithms (such as the RACE, VAN, or LAMS scales) utilize specific physical markers to differentiate LVO from minor lacunar strokes:

• Profound Hemiplegia: Complete flaccid paralysis of the arm and leg on one side.
• Conjugate Gaze Deviation: The patient's eyes are locked toward one side (typically gazing toward the side of the hemispheric cortical lesion) and cannot track across the midline.
• Global Aphasia or Severe Neglect: Complete loss of language comprehension/expression or complete hemi-inattention (the patient ignores an entire side of space, failing to recognize their own paralyzed limb).

Triage and Hospital Destination Routing

Identifying an LVO-compatible profile drastically impacts the emergency care system. Primary Stroke Centers (PSCs) can administer IV thrombolytics but often lack round-the-clock neurointerventional teams. Comprehensive Stroke Centers (CSCs) and Thrombectomy-Capable Stroke Centers (TSCs) have 24/7 endovascular suites. Prehospital LVO identification prompts EMS to bypass local community facilities (within approved regional transport time limits, typically 30 to 45 minutes) to bring the patient directly to an EVT-capable facility.

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Comparative Analysis: Ischemic vs. Hemorrhagic Stroke at Dispatch

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Protocol 28 Determinant Codes & Acuity Ladder

In the MPDS hierarchy, Protocol 28 classifies calls based on time elapsed from LKW and acute physiological risk:

+-------------------------------------------------------------------------+
|                     PROTOCOL 28 DETERMINANT CODES                       |
|                                                                         |
|   28-C-1:  Not alert                                                    |
|   28-C-2:  Abnormal breathing                                           |
|   28-C-3:  Sudden speech problems                                       |
|   28-C-4:  Sudden weakness or numbness (one side of the body)           |
|   28-C-5:  Sudden paralysis or facial droop (one side of the body)      |
|   28-C-6:  Sudden loss of balance or coordination                       |
|   28-C-7:  Sudden vision problems                                       |
|   28-C-8:  Sudden onset of severe headache                              |
|   28-C-9:  Stroke history                                               |
|   28-C-10: TIA (mini-stroke) history                                    |
|   28-C-11: Breathing normally, age >= 35                                |
|   28-C-12: Unknown status / other codes not applicable                  |
|   28-A-1:  Breathing normally, age < 35                                 |
|                                                                         |
|   NOTE: Protocol 28 has NO ECHO and NO DELTA level. CHARLIE is its      |
|   ceiling. A stroke patient who is not breathing normally is re-triaged |
|   on Protocol 31 (Unconscious/Fainting) or Protocol 9 (Arrest).         |
+-------------------------------------------------------------------------+

• There is no DELTA or ECHO code on Protocol 28. If the caller reports abnormal or agonal breathing, unresponsiveness, or apnea, the EMD does not stay on Protocol 28: the call moves to Protocol 31 (Unconscious / Fainting) or Protocol 9 (Cardiac or Respiratory Arrest). On Protocol 28 itself, abnormal breathing in an alert patient is 28-C-2.
• CHARLIE Level (28-C-1 through 28-C-12): Every acute stroke finding sits at CHARLIE. Positive Stroke Diagnostic findings map to specific codes — 28-C-3 sudden speech problems, 28-C-4 sudden weakness or numbness, 28-C-5 sudden paralysis or facial droop, 28-C-6 sudden loss of balance or coordination, 28-C-7 sudden vision problems, 28-C-8 sudden onset of severe headache. These codes initiate the ALS/BLS dispatch and the "Code Stroke" pre-notification to the emergency department.
• Transient Ischemic Attack: A TIA is 28-C-10 (TIA / mini-stroke history), still a CHARLIE code. While transient, a substantial proportion of TIA patients suffer a full stroke within days, so the evaluation remains urgent. 28-B-1 is "Unknown status," not TIA — a distinction the exam likes to test.
• The Time Window Lives in the Suffix, Not the Code: Protocol 28 appends a suffix combining the Stroke Diagnostic evidence grade (no test evidence, partial evidence, strong evidence, or clear evidence) with the time band since symptoms started (less than 2 hours, greater than 2 hours, or unknown). That suffix, not the sub-determinant, tells responders and the receiving stroke centre whether the patient may be inside a reperfusion window.

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Post-Dispatch Instructions (PDIs): Critical Positioning & Strict NPO

Following dispatch notification, the EMD must provide specific clinical care and scene management directives:

1. Head and Shoulder Elevation (15 to 30 Degrees)

"Keep them lying down with their head and shoulders raised slightly on a pillow, about 15 to 30 degrees, if it's comfortable for them."

• Clinical Rationale: Elevating the patient's head promotes cerebral venous drainage, attenuates intracranial pressure spikes, and reduces cerebral edema without compromising mean arterial cerebral perfusion pressure (CPP). Flat supine positioning elevates ICP, while excessive sitting (>45 degrees) can impair collateral blood flow across the ischemic penumbra in hypotensive states. Keep the head and neck aligned straight; do not allow the chin to slump onto the chest.

2. Strict NPO (Nil Per Os — Absolute Prohibition of Food, Drink, and Aspirin)

"Do not give them anything to eat or drink. Do not give them any medication—not even aspirin or water."

• Clinical Rationale (Aspiration): Stroke causes acute pharyngeal muscular hemiparesis and paralyzes the normal protective swallowing and gag reflexes. Administering oral water, juice, or pills leads directly to tracheal aspiration, foreign body airway obstruction, or catastrophic chemical/aspiration pneumonitis.
• Clinical Rationale (Aspirin Prohibition): In acute chest pain (Protocol 10), aspirin is lifesaving. In acute stroke, aspirin is strictly prohibited prehospital. Dispatchers and bystanders cannot distinguish ischemic stroke from hemorrhagic stroke over the telephone. If aspirin or other antiplatelet agents are administered to a patient with an active intracranial bleed, platelet aggregation is inhibited, causing rapid hematoma enlargement, brain herniation, and death. Aspirin may only be given after non-contrast head CT rules out hemorrhage in the hospital.

3. Scene Preparation & Medication Gathering

"Gather all of their medications or a list of them so the paramedics can see them. Unlock the front door and turn on the outside light."

• Collecting prescription bottles—specifically oral anticoagulants (e.g., apixaban, rivaroxaban, warfarin, dabigatran)—is essential, as anticoagulant presence alters hospital thrombolysis protocols and dictates immediate reversal agent administration.