Malignant hypertension


Malignant hypertension

Description, Causes and Risk Factors:

A malignant hypertension is an emergency condition in which elevated blood pressure results in target organ damage. The systems primarily involved are cardiovascular system (CV), renal system (RS), and the central nervous system (CNS). Malignant hypertension and accelerated hypertension are both hypertensive emergencies, with similar outcomes and therapies. In order to diagnose malignant hypertension, papilledema must be present.

Malignant hypertension is relatively uncommon, occurring in 1% of the hypertensive population. There is no gender bias, and patient range from infants to elderly. In Australia and New Zealand, the annual incidence of malignant hypertension as a cause of end-stage renal disease has increased sixfold over the last 25-30 years.

The pathogenesis of malignant hypertension is not well understood. However, at least two independent processes are known to contribute to the associated signs and symptoms.

    There is characteristic generalized fibrinoid necrosis (necrotising arteriolitis) of arterioles and small arteries, these changes leading in the glomerular vessels to rapidly progressive renal failure associated with proteinuria and hematuria. The fibrin deposited in the damaged vessels obstructs and damages red blood cells, resulting in microangiopathic hemolytic anemia.

  • There is a loss of cerebral blood flow autoregulation. In normal autoregulation, the cerebral vessels constrict and dilate when the mean arterial pressure is increased or decreased, respectively. When the mean arterial pressure rises above the autoregulatory range in severe HBP, cerebral arterial vasodilation occurs with resultant hyperperfusion and cerebral edema. This mechanism is more common in HBP that has developed over a relatively short period of time without the presence of protective vascular hypertrophy.

Symptoms:

The cardiac presentation of malignant hypertension is angina and/or myocardial infarction, congestive heart failure (CHF), or pulmonary edema. Orthostatic symptoms may be prominent.Renal disease may present as oliguria or any of the typical features of renal failure. Gastrointestinal symptoms are nausea and vomiting; in addition, diffuse arteriolar damage can result in microangiopathic hemolytic anemia.Neurologic presentations are occipital headache, cerebral infarction or hemorrhage, visual disturbance, or hypertensive encephalopathy. Patients may complain of blurred vision. A funduscopic examination may reveal flame-shaped retinal hemorrhages, soft exudates, or papilledema.

Diagnosis:

The history should include screening for symptoms of malignant hypertension, focusing on the cardiac, renal, and central nervous systems. Underlying medical disorders should be reviewed, including the possibility of eclampsia. The patient's medications and other drugs should be thoroughly reviewed; agents that may cause a hypertensive emergency include MAOIs and oral contraceptives, the withdrawal of beta-blockers, alpha-stimulants may also cause hypertensive emergency in some cases.

Initial laboratory studies include a complete blood cell (CBC) count and electrolytes (including calcium), blood urea nitrogen (BUN), creatinine, glucose, coagulation profile, and urinalysis. Other laboratory studies are indicated only as directed by the initial workup. These may include measurements for cardiac enzymes, thyroid-stimulating hormone (TSH), and 24-hour urine collection for vanillylmandelic acid (VMA) and catecholamines.

Renal function should be evaluated through urinalysis, complete chemistry profile, and CBC count. Expected findings include elevated BUN and creatinine, hyperphosphatemia, hyperkalemia or hypokalemia, glucose abnormalities, acidosis, hypernatremia, and evidence of microangiopathic hemolytic anemia and azotemic oliguric renal failure. Urinalysis may reveal proteinuria, microscopic hematuria, and red blood cell or hyaline casts.Sodium depletion is common and may be severe.

Imaging: Routine screening consists of a chest radiograph, which is useful for assessment of cardiac enlargement, pulmonary edema, or involvement of other thoracic structures, such as rib notching with aortic coarctation or a widened mediastinum with aortic dissection. Other studies, such as head CT scanning, transesophageal echocardiogram (TEE), and renal angiography, are indicated only as directed by the initial workup.

Electrocardiography: An ECG is an essential part of the evaluation to screen for ischemia, infarct, or evidence of electrolyte abnormalities or drug overdose. In the earliest stages of malignant hypertension, electrocardiogram and echocardiogram reveal left atrial enlargement and left ventricular hypertrophy.

Treatment:

Patients with malignant hypertension are usually admitted to an intensive care unit (ICU) for continuous cardiac monitoring, frequent assessment of neurologic status and urine output, and administration of intravenous antihypertensive medications and fluids. Patients typically have altered blood pressure autoregulation, and overzealous reduction of blood pressure to reference range levels may result in organ hypoperfusion.

In patients with stroke, cardiac compromise, or renal failure, appropriate consultation should be considered. In institutions with specialists in hypertension, prompt consultation may improve the overall control of blood pressure.

NOTE: The above information is educational purpose. The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition.

DISCLAIMER: This information should not substitute for seeking responsible, professional medical care.

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