A 58-year-old man presents with a blood pressure of 218/132 mmHg, severe headache, and blurred vision. Fundoscopy shows bilateral flame-shaped haemorrhages, cotton wool spots, and papilloedema. Serum creatinine is 2.4 mg/dL (baseline 1.0 mg/dL), urinalysis shows 2+ protein and RBC casts. ECG shows LVH. This is a hypertensive emergency. What is the target BP reduction in the FIRST HOUR of treatment, and which IV agent is PREFERRED when hypertensive emergency is associated with AKI and microangiopathic haemolytic anaemia?

• A Reduce BP to < 140/90 mmHg within 1 hour using IV labetalol as first-line
• B Reduce MAP by no more than 25% in the first hour; nicardipine or clevidipine preferred for hypertensive crisis with renal involvement and MAHA ✓
• C Reduce MAP by 25% in the first hour; IV sodium nitroprusside is the preferred agent for all hypertensive emergencies
• D Reduce diastolic BP to < 100 mmHg within 30 minutes using IV hydralazine boluses

Explanation

In hypertensive emergencies with end-organ damage, the AHA guidelines recommend reducing MAP by no more than 25% in the first hour (to avoid ischaemic injury from sudden pressure drop in autoregulation-impaired organs), then gradually to 160/100–110 mmHg over the next 2–6 hours, and to normal over the following 24–48 hours. For hypertensive emergencies with microangiopathic haemolytic anaemia (MAHA) and AKI (malignant hypertension with thrombotic microangiopathy), nicardipine (a dihydropyridine CCB) or clevidipine (ultra-short-acting CCB) are preferred IV agents — they are renally safe, titratable, and do not cause reflex tachycardia. Sodium nitroprusside causes cyanide toxicity in renal failure (unable to excrete thiocyanate). Labetalol is appropriate for many hypertensive emergencies but is relatively contraindicated in severe reactive airway disease.

Reference: Harrison's Principles of Internal Medicine, 21st ed.

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Written and medically reviewed by the StethoPrep medical team.