In hypertensive emergency with acute hypertensive encephalopathy, the target blood pressure reduction in the first hour according to current AHA/ACC guidelines is:
- A Reduce MAP by no more than 25% in the first hour ✓
- B Reduce SBP to < 120 mmHg within the first 30 minutes
- C Reduce BP by 50% over 2 hours to quickly restore cerebral perfusion
- D Maintain BP at >180/110 mmHg to preserve autoregulation until 24 hours
Correct answer: A. Reduce MAP by no more than 25% in the first hour
Explanation
In hypertensive emergencies (excluding ischaemic stroke and aortic dissection), the AHA/ACC guideline recommends reducing mean arterial pressure by no more than 25% in the first hour, then to 160/100–110 mmHg over the next 2–6 hours, then to normal over 24–48 hours. This cautious approach prevents precipitating cerebral ischaemia in patients whose autoregulatory curve has shifted rightward chronically — too-rapid reduction causes watershed ischaemia. Exception: aortic dissection requires SBP <120 mmHg rapidly; ischaemic stroke has specific thresholds.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
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