Emergency vs Urgency: End-Organ Damage Criteria
**Hypertensive emergency**: severely elevated BP (typically ≥180/120 mmHg) WITH acute end-organ damage: Neurological — hypertensive encephalopathy (headache, confusion, papilledema, seizures), ischemic stroke, hemorrhagic stroke, PRES (posterior reversible encephalopathy syndrome, occipital-parietal white matter edema on MRI). Cardiovascular — acute coronary syndrome (STEMI/NSTEMI), acute heart failure/pulmonary edema, aortic dissection (most urgent — SBP target <120 mmHg). Renal — acute kidney injury (thrombotic microangiopathy, hematuria, proteinuria). Ophthalmologic — papilledema, retinal hemorrhages/exudates (funduscopic exam essential). Hematologic — microangiopathic hemolytic anemia (MAHA), TTP-like picture. OB/GYN — severe preeclampsia/eclampsia (SBP ≥160 or DBP ≥110 with proteinuria/AKI). **Hypertensive urgency**: BP ≥180/120 without end-organ damage — patient asymptomatic or only headache without neurological signs. Treatment: oral antihypertensives (restart home medications, add oral amlodipine or clonidine), reduce BP over 24–48h, arrange close outpatient follow-up.
Treatment Principles and MAP Reduction Rule
**Hypertensive emergency**: IV antihypertensives in ICU setting with continuous arterial line monitoring. The MAP reduction rule: **DO NOT lower MAP >25% in the first hour** (except aortic dissection). Autoregulation of cerebral, renal, and coronary blood flow is reset at higher BPs in chronically hypertensive patients — rapid BP reduction causes ischemia (ischemic stroke, watershed infarcts, renal failure). After achieving 25% MAP reduction at 1 hour: reduce to 160/100 over next 2–6 hours, then normalize over 24–48h. **Special situations overriding the 25% rule**: Aortic dissection — SBP <120 mmHg ASAP (esmolol + sodium nitroprusside); Ischemic stroke WITHOUT thrombolysis candidate — treat only if BP >220/120 (keep higher BP to maintain penumbra perfusion); Ischemic stroke WITH tPA candidate — lower BP to <185/110 before giving tPA; SAH — maintain SBP <140–160 to prevent rebleeding; Acute pulmonary edema — aggressive BP reduction (SBP target 140) to reduce afterload.
IV Antihypertensive Agents and Indications
**Nicardipine** (IV dihydropyridine CCB): first-line for most hypertensive emergencies. Titratable infusion. Avoid in acute HF (reflex tachycardia). **Labetalol** (IV alpha + beta blocker): first-line for aortic dissection (with nitroprusside), hypertensive encephalopathy, pregnancy (safe); avoids reflex tachycardia. Contraindicated in acute decompensated HF, asthma, bradycardia. **Esmolol** (IV ultra-short-acting beta-1 blocker, t1/2 9 min): first-line with nitroprusside for aortic dissection (reduce HR ≤60 bpm, then add vasodilator). **Sodium nitroprusside** (arterial + venous vasodilator): useful for hypertensive emergency + pulmonary edema; risk of cyanide toxicity with prolonged high-dose use (give thiosulfate antidote). **Hydralazine** (IV vasodilator): used in pregnancy (along with labetalol, nifedipine oral); reflex tachycardia and unpredictable response limit use outside pregnancy. **Clevidipine** (IV dihydropyridine CCB, ultra-short half-life): useful in cardiac surgery and perioperative settings. **Fenoldopam** (DA1 receptor agonist): increases renal blood flow — useful in hypertensive emergency with AKI. **Phentolamine** (alpha-blocker): drug of choice for hypertensive crisis from catecholamine excess (pheochromocytoma, cocaine, MAOI interaction, clonidine withdrawal).