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- 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
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
- 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
Treat HTN and counsel patients on importance of compliance with antihypertensive treatment and dangers of stopping medications abruptly.
- 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 (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)
- Thrombotic thrombocytopenic purpura
- Severe burns
- Postoperative HTN
Commonly Associated Conditions
- Chronic renal failure
- Renovascular HTN
- Acute glomerulonephritis
- Renal vasculitis
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.