Hypertensive Emergencies

Description

• An acute elevation of blood pressure (BP) with evidence of rapid and progressive end-organ damage, particularly in the cardiovascular, renal, and CNS. Examples include acute renal injury, acute myocardial infarction (MI), acute stroke, acute heart failure. Severe hypertension (HTN) without evidence of end-organ damage (even in the presence of symptoms) is referred to as hypertensive urgency.
• Severe HTN or hypertensive crisis is defined as a diastolic BP of ≥120 mm Hg or systolic BP ≥180 mm Hg (1).
• System(s) affected: cardiovascular; nervous; pulmonary; renal
• Synonym(s): hypertensive crisis; severe HTN; malignant HTN; accelerated HTN

Epidemiology

Incidence
Incidence of hypertensive emergency: 1–2% of patients with HTN annually in the United States (2)

Prevalence

• ~1/3 of U.S. adults (>20 years) has HTN (2).
• Predominant age: elderly

Etiology and Pathophysiology

• Increased sympathetic tone leads to increased BP.
• Angiotensin II has multiple effects contributing to HTN and end-organ damage.
  • Stimulates sympathetic tone, aldosterone release, and antidiuretic hormone release
  • Chronic HTN induces vascular thickening and sclerosis.
  • Central effects include enhanced resorption of salt and water.
  • Chronic HTN shifts autoregulation of BP and cerebral blood flow.
• Renal disease
• Abrupt withdrawal from antihypertensives, especially clonidine
• Withdrawal from CNS depressants
• Medications: SSRIs, decongestants, appetite suppressants, steroids (including oral contraceptives), MAOI interaction with certain foods or drugs, drugs of abuse (cocaine, amphetamine)
• Eclampsia/preeclampsia
• Thrombotic thrombocytopenic purpura
• Pheochromocytoma
• Severe burns
• Postoperative HTN

Genetics

• Genetics: Risk of hypertensive emergency is higher in African Americans.
• Predominant sex: male > female

Risk Factors

• History of poorly controlled HTN
• Drug abuse
• Noncompliance with medications; abruptly stopping antihypertensive medication without supervision

General Prevention

Treat HTN and counsel patients on importance of compliance with antihypertensive treatment and dangers of stopping medications abruptly.

Commonly Associated Conditions

• Chronic renal failure
• Renovascular HTN
• Acute glomerulonephritis
• Renal vasculitis

Geriatric Considerations
Elderly patients may experience isolated systolic HTN due to decreased baroreceptor sensitivity.

Pediatric Considerations

• Usually associated with renal disease
• May present with abdominal pain
• Preferred agents for children include labetalol, nicardipine, and nitroprusside.

Pregnancy Considerations

• Labetalol, nicardipine, or hydralazine is preferred. Nitroprusside decreases placental blood flow, and cyanide metabolite crosses the placenta; may result in fetal toxicity with prolonged exposure
• Treat preeclampsia.