A 50-year-old woman presents with BP 220/138 mmHg, severe headache, papilloedema, serum creatinine rising from 0.9 to 2.4 mg/dL over 24 hours, and microangiopathic haemolytic anaemia on blood film. This is hypertensive emergency with acute hypertensive nephropathy. What is the recommended target BP reduction in the first hour, and why?
- A Reduce MAP by no more than 25% in the first hour, then gradually to 160/100 mmHg over the next 2–6 hours to avoid cerebral hypoperfusion ✓
- B Reduce BP by 50% in the first 30 minutes to protect the kidneys
- C Normalise BP to < 120/80 mmHg within 2 hours using aggressive IV therapy
- D Lower BP to < 160/100 mmHg within 30 minutes using oral amlodipine
Correct answer: A. Reduce MAP by no more than 25% in the first hour, then gradually to 160/100 mmHg over the next 2–6 hours to avoid cerebral hypoperfusion
Explanation
In hypertensive emergencies, autoregulation of cerebral and coronary blood flow is reset at higher pressures; overly rapid reduction risks watershed infarction, stroke, or cardiac ischaemia. The target is to reduce mean arterial pressure by no more than 25% within the first hour, then to 160/100–110 mmHg over the next 2–6 hours, with careful monitoring. IV labetalol, nicardipine, or clevidipine are preferred agents. Further gradual normalisation occurs over 24–48 hours.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
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Written and medically reviewed by the StethoPrep medical team.