Hypertensive Emergencies

Blood pressure is elevated, often markedly (systolic pressure > 180 mm Hg). Central nervous system symptoms include rapidly changing neurologic abnormalities (eg, confusion, transient cortical blindness, hemiparesis, hemisensory defects, seizures). Cardiovascular symptoms include chest pain and dyspnea. Renal involvement may be asymptomatic, although severe azotemia due to advanced renal failure may cause lethargy or nausea.

Physical examination focuses on target organs, with neurologic examination, funduscopy, and cardiovascular examination. Global cerebral deficits (eg, confusion, obtundation, coma), with or without focal deficits, suggest encephalopathy; normal mental status with focal deficits suggests stroke Overview of Stroke Strokes are a heterogeneous group of disorders involving sudden, focal interruption of cerebral blood flow that causes neurologic deficit. Strokes can be Ischemic (80%), typically resulting... read more . Severe retinopathy Hypertensive Retinopathy Hypertensive retinopathy is retinal vascular damage caused by hypertension. Signs usually develop late in the disease. Funduscopic examination shows arteriolar constriction, arteriovenous nicking... read more (sclerosis, cotton-wool spots, arteriolar narrowing, hemorrhage, papilledema) is usually present with hypertensive encephalopathy, and some degree of retinopathy is present in many other hypertensive emergencies. Jugular venous distention, basilar lung crackles, and a 3rd heart sound suggest pulmonary edema Pulmonary Edema Pulmonary edema is acute, severe left ventricular failure with pulmonary venous hypertension and alveolar flooding. Findings are severe dyspnea, diaphoresis, wheezing, and sometimes blood-tinged... read more . Asymmetry of pulses between arms suggests aortic dissection Aortic Dissection Aortic dissection is the surging of blood through a tear in the aortic intima with separation of the intima and media and creation of a false lumen (channel). The intimal tear may be a primary... read more .

Testing typically includes ECG, urinalysis, and serum BUN and creatinine.

Patients with neurologic findings require head CT to diagnose intracranial bleeding, edema, or infarction.

Patients with chest pain or dyspnea require and ECG and chest x-ray.

ECG abnormalities suggesting acute target-organ damage include acute ischemia.

Urinalysis abnormalities typical of renal involvement include red blood cells (RBCs), RBC casts, and proteinuria.

Diagnosis is based on the presence of a very high BP and findings of target-organ involvement.

Hypertensive emergencies are treated in an ICU; blood pressure is progressively (although not abruptly) reduced using a short-acting, titratable IV medication. Choice of medication and speed and degree of reduction vary somewhat with the target organ involved, but generally a 20 to 25% reduction in MAP over an hour or so is appropriate, with further titration based on symptoms. Achieving “normal” BP urgently is not necessary. Typical first-line medications include nitroprusside, fenoldopam, nicardipine, and labetalol (see table Parenteral Drugs for Hypertensive Emergencies Parenteral Drugs for Hypertensive Emergencies ). Nitroglycerin alone is less potent.

Oral medications are not indicated because onset is variable and the medications are difficult to titrate. Although short-acting oral nifedipine reduces blood pressure rapidly, it may lead to acute hypotension, which may lead to cardiovascular and cerebrovascular ischemic events (sometimes fatal) and is therefore not recommended.

Clevidipine is an ultra-short-acting (within 1 to 2 minutes), 3rd-generation calcium channel blocker that reduces peripheral resistance without affecting venous vascular tone and cardiac filling pressures. Clevidipine is rapidly hydrolyzed by blood esterases and, thus, its metabolism is not affected by renal or hepatic function. It has been shown to be effective and safe in the control of perioperative hypertension and hypertensive emergencies and was associated with lower mortality than nitroprusside.

Starting dose of clevidipine is 1 to 2 mg/hour, doubling the dose every 90 seconds until approaching target BP, at which time dose is increased by less than double every 5 to 10 minutes. Clevidipine may thus be preferred over nitroprusside for most hypertensive emergencies, although it should be used with caution in acute heart failure with reduced ejection fraction Heart failure with reduced ejection fraction (HFrEF) Heart failure (HF) is a syndrome of ventricular dysfunction. Left ventricular (LV) failure causes shortness of breath and fatigue, and right ventricular (RV) failure causes peripheral and abdominal... read more as it may have negative inotropic effects. If clevidipine is not available, then fenoldopam, nitroglycerin, or nicardipine are reasonable alternatives.

Fenoldopam is a peripheral dopamine-1 agonist that causes systemic and renal vasodilation and natriuresis. Onset is rapid and half-life is brief, making it an effective alternative to nitroprusside, with the added benefit that it does not cross the blood-brain barrier. Initial dosage is 0.1 mcg/kg/minute IV infusion, titrated upward by 0.1 mcg/kg every 15 minutes to a maximum of 1.6 mcg/kg/minute.

Labetalol is a beta-blocker with some alpha-1-blocking effects, thus causing vasodilation without the typical accompanying reflex tachycardia. It can be given as a constant infusion or as frequent boluses; use of boluses has not been shown to cause significant hypotension. Labetalol is used during pregnancy, for intracranial disorders requiring BP control, and after myocardial infarction. Infusion is 0.5 to 2 mg/minute, titrated upward to a maximum of 4 to 5 mg/minute. Boluses begin with 20 mg IV followed every 10 minutes by 40 mg, then 80 mg (up to 3 doses) to a maximum total of 300 mg. Adverse effects are minimal, but because of its beta -blocking activity, labetalol should not be used for hypertensive emergencies in patients with asthma Asthma Asthma is a disease of diffuse airway inflammation caused by a variety of triggering stimuli resulting in partially or completely reversible bronchoconstriction. Symptoms and signs include dyspnea... read more . Low doses may be used for left ventricular failure if nitroglycerin is given simultaneously.

Nitroprusside is a venous and arterial dilator, reducing preload and afterload; thus, it is the most useful for hypertensive patients with heart failure Heart Failure (HF) Heart failure (HF) is a syndrome of ventricular dysfunction. Left ventricular (LV) failure causes shortness of breath and fatigue, and right ventricular (RV) failure causes peripheral and abdominal... read more . It is also used for hypertensive encephalopathy and, with beta-blockers, for aortic dissection Aortic Dissection Aortic dissection is the surging of blood through a tear in the aortic intima with separation of the intima and media and creation of a false lumen (channel). The intimal tear may be a primary... read more . Starting dose is 0.25 to 1.0 mcg/kg/minute titrated in increments of 0.5 mcg/kg to a maximum of 8 to 10 mcg/kg/minute; maximum dose is given for ≤ 10 minutes to minimize risk of cyanide toxicity. The drug is rapidly broken down into cyanide and nitric oxide (the active moiety). Cyanide is detoxified to thiocyanate. However, administration of > 2 mcg/kg/minute can lead to cyanide accumulation with toxicity to the central nervous system and heart; manifestations include agitation, seizures, cardiac instability, and an anion gap metabolic acidosis.

Prolonged administration of nitroprusside (> 1 week or, in patients with renal insufficiency, 3 to 6 days) leads to accumulation of thiocyanate, with lethargy, tremor, abdominal pain, and vomiting. Other adverse effects include transitory elevation of hair follicles (cutis anserina) if BP is reduced too rapidly. Thiocyanate levels should be monitored daily after 3 consecutive days of therapy, and the medication should be stopped if the serum thiocyanate level is > 12 mg/dL (> 2 mmol/L). Because nitroprusside is broken down by ultraviolet light, the IV bag and tubing are wrapped in an opaque covering. Given data showing increased mortality with nitroprusside compared to clevidipine, nitroglycerin, and nicardipine, nitroprusside should probably not be used when other alternatives are available.

Nitroglycerin is a vasodilator that affects veins more than arterioles. It can be used to manage hypertension during and after coronary artery bypass graft surgery Coronary Artery Bypass Grafting (CABG) Frontal and lateral chest x-ray of a patient post coronary artery bypass surgery showing sternal sutures (black arrow) and surgical clips (red arrow). Coronary artery bypass grafting (CABG)... read more , acute myocardial infarction Acute Myocardial Infarction (MI) Acute myocardial infarction is myocardial necrosis resulting from acute obstruction of a coronary artery. Symptoms include chest discomfort with or without dyspnea, nausea, and/or diaphoresis... read more , unstable angina pectoris Unstable Angina Unstable angina results from acute obstruction of a coronary artery without myocardial infarction. Symptoms include chest discomfort with or without dyspnea, nausea, and diaphoresis. Diagnosis... read more , and acute pulmonary edema Pulmonary Edema Pulmonary edema is acute, severe left ventricular failure with pulmonary venous hypertension and alveolar flooding. Findings are severe dyspnea, diaphoresis, wheezing, and sometimes blood-tinged... read more . IV nitroglycerin is preferable to nitroprusside for patients with severe coronary artery disease because nitroglycerin increases coronary flow, whereas nitroprusside tends to decrease coronary flow to ischemic areas, possibly because of a “steal” mechanism. Starting dose is 10 to 20 mcg/minute titrated upward by 10 mcg/minute every 5 minutes to maximum antihypertensive effect.

For long-term BP control, nitroglycerin must be used with other medications. The most common adverse effect is headache (in about 2%); others include tachycardia, nausea, vomiting, apprehension, restlessness, muscular twitching, and palpitations.

Nicardipine, a dihydropyridine calcium channel blocker with less negative inotropic effects than nifedipine, acts primarily as a vasodilator. It is most often used for postoperative hypertension and during pregnancy. Dosage is 5 mg/hour IV, increased every 15 minutes to a maximum of 15 mg/hour. It may cause flushing, headache, and tachycardia; it can decrease glomerular filtration rate (GFR) in patients with renal insufficiency.

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