🩸 Chapter 87: Hypertensive Crises

Hypertensive emergency (end-organ damage) vs urgency · Cerebral autoregulation · Goal: reduce SBP by ≤25% over first 8h · IV agents: nicardipine, labetalol, sodium nitroprusside · Avoid nifedipine sublingual (precipitous hypotension) · Captopril contraindicated in bilateral renal artery stenosis · Post-coarctectomy hypertension

🔍 Core Concepts: Hypertensive Crises

📌 Definitions
Hypertensive emergency: severe hypertension + acute end-organ damage (CNS, heart, kidneys, retina). Hypertensive urgency: severe hypertension without end-organ damage. Both require prompt treatment, emergency in PICU.
🧠 Cerebral Autoregulation
Normally CBF constant at MAP 60-160 mmHg. Chronic hypertension shifts curve right. Too rapid BP reduction → cerebral ischaemia. Goal: reduce SBP by ≤25% over first 8h, then gradual normalisation over 24-72h.
💊 IV Antihypertensives (Emergency)
Nicardipine (1-3 mcg/kg/min) — calcium channel blocker. Labetalol (0.2-1 mg/kg IV) — alpha+beta blocker. Sodium nitroprusside (0.3-10 mcg/kg/min) — potent, risk cyanide toxicity. Fenoldopam, enalaprilat.
⚠️ Avoid Sublingual Nifedipine
Sublingual nifedipine causes precipitous hypotension and cerebral ischaemia. Use oral nifedipine (0.2-0.5 mg/kg) only for urgency with caution.
📊 Aetiology
Most common: renal parenchymal disease (GN, HUS), renovascular (fibromuscular dysplasia), coarctation of aorta, endocrine (pheochromocytoma), drugs (cyclosporine, tacrolimus).
🩺 Evaluation
Fundoscopy (papilloedema, haemorrhages). CBC, Cr, urinalysis, electrolytes, renal ultrasound, echocardiogram. CXR for coarctation. Further tests based on suspicion.

🩺 Stepwise Approach: Hypertensive Emergency

1
Confirm severe hypertension & assess end-organ damage
BP >95th percentile + 30 mmHg (stage 2). Look for encephalopathy (headache, seizures, altered sensorium), cardiac (LV failure, chest pain), renal (oliguria, elevated Cr), retinal changes (papilloedema, haemorrhages).
2
Admit to PICU, place arterial line
Continuous invasive BP monitoring. Treat pain/anxiety (can elevate BP). Ensure adequate sedation.
3
Initiate IV antihypertensive with gradual reduction
Goal: reduce SBP by ≤25% over first 8 hours. Then gradual normalisation over 24-72 hours. Avoid precipitous drop.
4
Choose IV agent based on clinical scenario
Nicardipine (first-line, easy titration). Labetalol (good in pregnancy, asthma caution). Sodium nitroprusside (potent, monitor cyanide). Fenoldopam (if renal impairment). Enalaprilat (if LV failure, avoid in bilateral renal artery stenosis).
5
Diagnose underlying aetiology
Renal ultrasound (size, echogenicity, Doppler for renal artery stenosis). Echocardiogram (coarctation, LVH). Urinalysis, Cr, electrolytes, renin, aldosterone, catecholamines if indicated.
6
Transition to oral agents
Once stable (24-48h), add oral antihypertensives (captopril, nifedipine, amlodipine) and wean IV. Avoid sublingual nifedipine (precipitous hypotension).