Ischemic Stroke

The brain loses 1.9 million neurons every minute blood flow is blocked. Recognizing an ischemic stroke and understanding the treatment window separates salvageable brain from permanent damage.

Ischemic stroke accounts for roughly 87% of all strokes and results from a thrombus or embolus occluding a cerebral artery. The two main subtypes matter clinically: thrombotic strokes often develop gradually (sometimes during sleep) with a stepwise progression of deficits, while embolic strokes strike suddenly with maximal deficit at onset — commonly originating from atrial fibrillation. The critical intervention is IV alteplase (tPA), eligible within 4.5 hours of symptom onset (or last known well time). Before administration, confirm a CT scan is negative for hemorrhage — tPA in a hemorrhagic stroke can be catastrophic and is absolutely contraindicated. Key exclusion criteria include major surgery within 14 days, active internal bleeding, platelet count below 100,000, INR above 1.7, and BP above 185/110 mmHg. Blood pressure is managed carefully: permissive hypertension is allowed acutely (up to 220/120 if no tPA given) because the brain needs perfusion pressure to feed the ischemic penumbra — the at-risk tissue surrounding the infarct core. Post-tPA, BP must stay below 180/105 for 24 hours. Aspirin is initiated within 24–48 hours of onset but held for 24 hours after tPA. Post-tPA nursing care includes neuro checks every 15 minutes for the first 2 hours, every 30 minutes for 6 hours, then hourly for 16 hours — monitor for hemorrhagic conversion (sudden neuro decline, severe headache, new hypertension). Perform a dysphagia screen before any oral intake. Mechanical thrombectomy extends the window up to 24 hours for large vessel occlusions in select patients. The NIH Stroke Scale quantifies deficit severity and guides treatment decisions.

Key Distinctions

Don't confuse permissive hypertension in ischemic stroke (allow higher BP to perfuse penumbra) with hemorrhagic stroke management (aggressively lower BP to reduce bleeding). Students often think any stroke contraindicates tPA — only hemorrhagic stroke does. Thrombotic strokes evolve stepwise, often overnight; embolic strokes present with sudden maximal deficit — this onset pattern helps identify the subtype. A TIA resolves completely (usually within minutes, by definition within 24 hours) with no infarct on imaging; a completed ischemic stroke shows persistent deficits and tissue death. Both require urgent workup, but TIA is a warning — not a pass.

Clinical Pearl

Time is brain. No tPA without a CT first — you're ruling out the bleed, not confirming the clot. Last known well time is your clock, not when symptoms were discovered.