Description

• Numerous terms, often overlapping. Some definitions include a specific BP reading; others emphasize acute change in the BP or the presence of specific clinical syndromes.
• Severe HTN is defined as a diastolic BP of ≥115 mm Hg (15.3 kPa).
• A hypertensive emergency occurs only when an acute elevation of BP causes rapid and progressive end-organ damage, particularly in the cardiovascular, renal, and CNS.
• System(s) affected: Cardiovascular; Nervous; Pulmonary; Renal
• Synonym(s): Hypertensive crisis; Severe HTN; Malignant HTN; Accelerated HTN; Hypertensive emergency

Epidemiology

Incidence
Incidence of hypertensive emergency: 1% of patients with hypertension annually in the US

• Overall prevalence of HTN in the US: 29.3% based on a 2003–2004 survey data
• Predominant age: Elderly

Risk Factors

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

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

General Prevention

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

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.

Etiology

• Renal disease
• Abrupt withdrawal from antihypertensives, especially clonidine (Catapres)
• 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

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.

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

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