13.2 Hypertensive Emergencies & Ruptured Abdominal Aortic Aneurysm
Key Takeaways
In most hypertensive emergencies, mean arterial pressure is reduced by no more than about 25% in the first hour, then toward 160/100 mmHg over the next 2 to 6 hours.
Aortic dissection is the exception that requires rapid reduction to a systolic pressure below 120 mmHg and a heart rate below 60 bpm, with beta-blockade before any vasodilator.
Pheochromocytoma crisis is treated with phentolamine or nicardipine first; giving a beta-blocker before alpha-blockade causes unopposed alpha stimulation and a hypertensive catastrophe.
Nitroprusside causes cyanide and thiocyanate accumulation, especially at high doses, prolonged infusion, or with kidney impairment, and raises intracranial pressure.
Ruptured abdominal aortic aneurysm is managed with permissive hypotension (systolic around 70 to 90 mmHg while the patient is conscious) and immediate transfer for repair.
Emergency Versus Urgency
- Hypertensive emergency: severe hypertension (usually above 180/120 mmHg) with acute target-organ injury. The absolute number matters less than the evidence of damage.
- Hypertensive urgency: severe hypertension without acute target-organ injury. Treat with oral agents over days and arrange follow-up. Rapid intravenous lowering in this setting causes harm.
Chronic hypertension shifts cerebral autoregulation rightward, so a sudden fall in pressure can cause ischemia even at a "normal" blood pressure. The default is therefore to lower the mean arterial pressure by no more than about 25% in the first hour, then toward 160/100 mmHg over 2 to 6 hours, and to normal over 24 to 48 hours. Several conditions override that default.
Matching the Target to the Target Organ
| Condition | Target | Preferred agents | Avoid |
|---|---|---|---|
| Acute aortic dissection | Systolic below 120 mmHg and heart rate below 60 bpm within minutes | IV esmolol or labetalol first, then nicardipine or nitroprusside | Vasodilator before rate control (reflex tachycardia raises shear stress); hydralazine |
| Acute pulmonary edema (SCAPE) | Rapid, large reduction in afterload | High-dose nitroglycerin, nitroprusside, plus noninvasive ventilation and loop diuretic | Beta-blockers (negative inotropy in decompensated failure) |
| Acute coronary syndrome | Relieve ischemia; systolic below about 140 mmHg | Nitroglycerin plus beta-blocker | Hydralazine; nitrates with recent phosphodiesterase-5 inhibitor use or inferior infarction with RV involvement |
| Acute ischemic stroke | No treatment unless above 220/120 mmHg (or above 185/110 mmHg before thrombolysis, then below 180/105 mmHg) | Labetalol, nicardipine, clevidipine | Aggressive lowering, which extends the infarct |
| Intracerebral hemorrhage | Smooth lowering toward systolic 130 to 150 mmHg | Nicardipine, clevidipine, labetalol | Nitroprusside (raises intracranial pressure); drops below 130 mmHg |
| Aneurysmal subarachnoid hemorrhage | Avoid hypotension and extreme hypertension or variability; no single proven target | Short-acting titratable agents | Prolonged hypotension |
| Hypertensive encephalopathy | Lower mean pressure by 20% to 25% in the first hour | Nicardipine, labetalol, clevidipine | Overcorrection |
| Acute kidney injury or sclerodermal crisis | Gradual control; ACE inhibitor is specific in scleroderma renal crisis | Nicardipine, clevidipine, fenoldopam; captopril for scleroderma | Nitroprusside with kidney failure (thiocyanate) |
| Severe preeclampsia or eclampsia | Systolic below 160 mmHg and diastolic below 110 mmHg; magnesium for seizure prophylaxis | IV labetalol, hydralazine, oral nifedipine | ACE inhibitors, ARBs, nitroprusside (fetal cyanide risk) |
| Catecholamine excess (pheochromocytoma, cocaine or amphetamine, clonidine withdrawal, MAO inhibitor crisis) | Control the alpha effect first | Phentolamine, nicardipine, clevidipine; benzodiazepines for sympathomimetic toxicity | Beta-blocker alone (unopposed alpha vasoconstriction) |
| Perioperative hypertension | Pressure close to baseline | Esmolol, nicardipine, clevidipine | Long-acting agents when swings are expected |
Drug Notes
- Nicardipine: 5 mg/h, titrated by 2.5 mg/h every 5 to 15 minutes, up to 15 mg/h. Predictable, no reflex tachycardia requirement, but it has a long context-sensitive half-life.
- Clevidipine: an ultrashort-acting dihydropyridine in a lipid emulsion; useful when minute-to-minute control is needed. Watch the lipid load and avoid it with soy or egg allergy.
- Labetalol: combined alpha-1 and beta blockade, dosed 10 to 20 mg IV then doubled every 10 minutes. Avoid it in decompensated heart failure, bradycardia, and severe asthma.
- Esmolol: a very short-acting beta-1 blocker ideal for dissection or when beta-blocker tolerance is uncertain.
- Nitroglycerin: predominantly venodilation at low dose, arterial at high dose. First choice for ischemia and acute pulmonary edema; tachyphylaxis develops within 24 to 48 hours.
- Nitroprusside: balanced arterial and venous dilation with instant onset. It releases cyanide, which is metabolized to thiocyanate. Risk rises with doses above about 2 micrograms/kg/min, prolonged infusion, and kidney or liver impairment. Suspect toxicity with a rising lactate, a narrowed arteriovenous oxygen difference, and altered mental status. Treat with sodium thiosulfate and hydroxocobalamin; co-infusion of thiosulfate reduces risk. It also raises intracranial pressure and causes coronary steal.
- Hydralazine: unpredictable, long-lasting, and causes reflex tachycardia; it is a poor choice in dissection or coronary disease, but is still used in pregnancy.
- Fenoldopam: a dopamine-1 agonist that increases renal blood flow; avoid it with glaucoma.
- Enalaprilat: useful in high-renin states; avoid it in pregnancy, bilateral renal artery stenosis, and hyperkalemia.
Warning
In clonidine withdrawal, restart clonidine. Giving a beta-blocker first worsens the hypertension through unopposed alpha stimulation, the same trap as in pheochromocytoma.
Hypertensive Encephalopathy and PRES
Hypertensive encephalopathy presents with headache, confusion, seizures, and visual disturbance. MRI typically shows posterior reversible encephalopathy syndrome (PRES): vasogenic edema in the parieto-occipital white matter. Lower the pressure by 20% to 25% in the first hour, control seizures, and remove precipitants such as calcineurin inhibitors, VEGF inhibitors, and other cytotoxic drugs. Symptoms usually improve within days as the edema resolves; permanent deficits occur with hemorrhage or infarction.
Ruptured Abdominal Aortic Aneurysm
- Presentation: the classic triad of abdominal or back pain, hypotension, and a pulsatile mass is incomplete in most patients. Suspect it in any older patient with sudden abdominal or flank pain and hypotension, including presentations mimicking renal colic.
- Diagnosis: bedside ultrasound confirms an aneurysm (a diameter above 3 cm) in seconds, although it cannot reliably exclude rupture. CT angiography defines anatomy for endovascular repair in the stable patient; an unstable patient goes directly to the operating room.
- Resuscitation:
- Permissive hypotension: target a systolic pressure of roughly 70 to 90 mmHg while mentation is preserved. Raising blood pressure dislodges clot and increases bleeding.
- Avoid large crystalloid volumes; use a balanced massive transfusion approach.
- Keep the patient warm, correct coagulopathy, and give tranexamic acid when trauma protocols apply.
- Immediate transfer for repair. Endovascular repair (EVAR) has lower perioperative mortality than open repair in suitable anatomy; both are acceptable, and delay for imaging in an unstable patient is dangerous.
- After repair, watch for:
- Abdominal compartment syndrome, particularly after EVAR for rupture.
- Colonic ischemia, suggested by bloody diarrhea and acidosis (perform flexible sigmoidoscopy).
- Spinal cord ischemia, kidney failure, and distal embolization.
- Inflammatory and mycotic aneurysms (for example, Salmonella) present with fever and pain and need antibiotics with repair.
A 54-year-old man presents with tearing chest pain radiating to his back, a blood pressure of 206/112 mmHg, and CT angiography showing a type B aortic dissection. What is the correct initial pharmacologic sequence?
Start sodium nitroprusside alone to achieve a systolic pressure below 120 mmHg as quickly as possible
Start intravenous esmolol or labetalol first, then add nicardipine or nitroprusside if the target is not reached
Start hydralazine 20 mg intravenously every 20 minutes until the pain resolves
Start nicardipine and withhold beta-blockade until the heart rate exceeds 110 bpm
A 46-year-old woman has episodic headache, palpitations, and diaphoresis, and arrives with a blood pressure of 248/134 mmHg, chest pain, and pulmonary edema. Plasma metanephrines drawn previously were markedly elevated. Which initial intravenous therapy is most appropriate?
Metoprolol 5 mg intravenously, repeated every 5 minutes
Phentolamine with nicardipine as needed for ongoing control
Esmolol infusion titrated to a heart rate below 60 bpm
Hydralazine 20 mg intravenously with furosemide
A 78-year-old man with a known 6.2 cm abdominal aortic aneurysm presents with sudden severe flank pain and a blood pressure of 78/52 mmHg. He is pale but alert and oriented. Bedside ultrasound confirms the aneurysm with surrounding fluid. The vascular surgery team is activated. Which resuscitation strategy is most appropriate while awaiting transfer to the operating room?
Rapidly infuse 2 liters of crystalloid to restore a systolic pressure above 120 mmHg
Start a norepinephrine infusion targeting a mean arterial pressure of 75 mmHg
Allow permissive hypotension around a systolic of 70 to 90 mmHg while he remains conscious, using blood products as needed
Delay operative transfer until CT angiography and a complete coagulation panel are available
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