Agents for hypertensive emergencies

Definition and Initial Goals

A hypertensive emergency is a severe elevation in blood pressure accompanied by acute target-organ injury such as encephalopathy, intracerebral hemorrhage, acute coronary syndrome, acute pulmonary edema, aortic dissection, or acute kidney injury. Management requires admission to an intensive or high-dependency unit and use of rapid-acting intravenous (IV) antihypertensive agents.

General principles of reduction:

• Lower mean arterial pressure by about 20–25% within the first hour.

• Reduce to around 160/100–110 mmHg over the next 2–6 hours.

• Carefully approach normal levels over 24–48 hours, except in conditions like aortic dissection where more aggressive lowering is needed.

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Main IV Drug Classes and Agents

1. Dihydropyridine Calcium Channel Infusions

Nicardipine (IV infusion)

• Starting dose: 5 mg/h.

• Increase by 2.5 mg/h every 5–15 min to effect.

• Maximum: 15 mg/h.

• Often preferred in neurologic hypertensive crises (encephalopathy, stroke) and postoperative hypertension.

Clevidipine (IV emulsion)

• Starting dose: 1–2 mg/h.

• Double dose at short intervals (every 1–2 min) until effect, then titrate more slowly.

• Maximum: 16 mg/h.

• Contraindicated in severe aortic stenosis, egg/soy allergy, and defective lipid metabolism.

Fenoldopam (selective dopamine-1 agonist)

• Starting dose: 0.1–0.3 mcg/kg/min.

• Increase by 0.05–0.1 mcg/kg/min every 15 min as needed.

• Maximum: about 1.6 mcg/kg/min.

• Particularly useful in patients with renal dysfunction; avoid in glaucoma.

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2. Nitrates

Nitroglycerin (IV infusion)

• Starting dose: 5–10 mcg/min.

• Increase by 5–10 mcg/min every 3–5 min to effect.

• Most patients require 50–200 mcg/min.

• Best choice in acute pulmonary edema and acute coronary syndromes.

Sodium Nitroprusside (IV infusion)

• Starting dose: 0.3 mcg/kg/min.

• Effective range: 0.5–3 mcg/kg/min.

• Maximum: 10 mcg/kg/min for ≤10 minutes.

• Extremely rapid onset and offset, but risk of cyanide/thiocyanate toxicity. Avoid in renal/hepatic failure and pregnancy.

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3. Beta-Adrenergic Blockers

Esmolol (ultrashort-acting IV infusion)

• Bolus: 500 mcg/kg over 1 min, followed by 50 mcg/kg/min.

• Increase in 50 mcg/kg/min increments every 4–5 min.

• Maximum: 200–300 mcg/kg/min.

• Especially useful in aortic dissection and tachyarrhythmia-associated hypertension.

Labetalol (combined α and β blocker)

• Bolus protocol: 20 mg IV, then 40–80 mg every 10 min up to a cumulative maximum of 300 mg.

• Infusion: 0.5–2 mg/min continuous IV.

• Suitable in pregnancy and neurologic emergencies. Avoid in asthma, bradycardia, or acute pulmonary edema.

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4. Other Vasodilators and Adjuncts

Hydralazine (IV bolus)

• Dose: 10–20 mg IV every 4–6 hours as needed.

• Primarily used in pregnancy-related hypertensive emergencies (eclampsia, preeclampsia).

• Onset less predictable, risk of reflex tachycardia.

Enalaprilat (IV ACE inhibitor)

• Dose: 1.25 mg IV every 6 hours, titrated.

• Useful in hypertensive emergencies related to high renin states, but avoid in acute myocardial infarction, pregnancy, and bilateral renal artery stenosis.

Phentolamine (IV α-blocker)

• Dose: 5–15 mg IV bolus.

• Indicated for hypertensive crises due to catecholamine excess (pheochromocytoma, cocaine, MAOI crisis).

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Condition-Specific Choices

• Aortic dissection: Rapid β-blockade (esmolol or labetalol) + vasodilator (nitroprusside) to reduce shear stress.

• Acute coronary syndrome: Nitroglycerin ± β-blocker.

• Acute pulmonary edema: Nitroglycerin or nitroprusside (if blood pressure allows).

• Pregnancy (eclampsia, preeclampsia): Labetalol, hydralazine, or nifedipine.

• Acute ischemic stroke: Lower BP only if ≥220/120 mmHg or before thrombolysis (>185/110 mmHg); use nicardipine or labetalol.

• Intracerebral hemorrhage: Nicardipine, clevidipine, or labetalol to carefully reduce BP.

• Catecholamine crisis: Phentolamine or nicardipine.