Etiology

The etiology of hypertension is unknown, but there are several contributing factors. Secretion of excess sodium-retaining hormones and vasoconstriction substances, high sodium intake, obesity, diabetes mellitus, excessive alcohol intake, and sympathetic nervous system activity all contribute to elevated blood pressure.

There are two major types of hypertension: primary (idiopathic or essential) and secondary hypertension. Persons with a family history of hypertension are at risk for developing primary hypertension. Approximately 90% to 95% of all cases of hypertension are primary.

In 5% to 8% the hypertension is secondary to another disorder. Acute stress, excessive alcohol intake, sickle cell disease, arteriosclerosis, coarctation of the aorta, eclampsia of pregnancy, renal disorders, endocrine disorders, and neurologic disorders are examples of secondary causes. Amphetamine use, chronic nonsteroidal anti-inflammatory drug (NSAID) use, and tyramine-containing foods such as beer and wine taken with monoamine oxidase (MAO) inhibitors contribute to secondary hypertension. Female hormone therapy and nicotine use appear to be contributing factors in some people. If the underlying disorder can be detected and treated successfully, the problem of secondary hypertension is eliminated or more easily controlled. If no underlying disease can be identified as elevating the patient’s blood pressure, the patient is said to have primary hypertension.

The rising incidence of childhood obesity has resulted in an increase in the incidence of hypertension. Health promotion activities targeting nutrition and exercise habits of children are increasing.

Pathophysiology

Blood pressure equals the amount of blood pumped out of the heart multiplied by the systemic vascular resistance. If the diameter of blood vessels becomes smaller because of atherosclerosis or vasoconstriction, blood pressure increases in an effort to force the blood through the smaller opening. If there is an increase in the volume (amount) or viscosity (thickness or consistency) of fluid in the blood vessels, the pressure within the vessels increases and the heart must work harder to pump the fluid through the vessels. A pathologic response to stress can result in an elevation in blood pressure by stimulating the sympathetic nervous system and causing peripheral vasoconstriction and increased heart rate.

Insulin, glucose, and lipoprotein abnormalities are common in primary hypertension. High blood insulin concentration stimulates sympathetic nervous system activity contributing to vasoconstriction.

Signs, Symptoms, and Diagnosis

Hypertension has been called the “silent killer” because in early stages it does not usually cause discomfort or any other subjective signs and symptoms to indicate its presence. About one third of those who have hypertension are not aware of it. Signs may appear only in the later stages when damage has been done to the target organs—that is, the kidney (renal ischemia and nephrosclerosis), brain (arteriosclerosis and microaneurysms), aorta (aortic aneurysm), eyes (retinal damage), and heart (left ventricular hypertrophy and reduced cardiac output). Patients with symptoms may complain of headache, dizziness, blurred vision, blackouts, irritability, angina, dyspnea, or fatigue.

Hypertensive patients develop coronary heart disease at a rate two to three times greater than that of persons with normal blood pressure. Examination of the blood vessels of the retina will reveal any damage to the retinal vessels. This retinal assessment gives an indication about how much damage the high blood pressure has done to vessels throughout the body. If retinal damage has occurred, it is an indication that the person’s hypertension is moderate to severe.

Diagnosis is by blood pressure readings on at least two occasions 2 weeks apart. An electrocardiogram (ECG) and cardiac stress test may be ordered to determine whether any damage has been done to the coronary arteries or to the heart muscle.

Treatment

The goals of treatment are (1) reduction of high blood pressure and (2) long-term control to decrease the risk of stroke, heart attack, loss of vision, and kidney disease. The target is to control blood pressure at or below 120/80 mm Hg. Treatment is individualized, using a stepped-care approach. For mild hypertension, smoking cessation, weight reduction, sodium restriction, alcohol restriction, exercise, a low-fat diet, and stress control are instituted. Sodium should be kept to less than 2400 mg/day with the DASH (Dietary Approaches to Stop Hypertension) eating plan. Alcohol intake should not exceed one serving of liquor, wine, or beer for women per day or two servings for men per day. Aerobic exercise of 30 to 45 minutes most days of the week is recommended. If blood pressure is still high, a diuretic is added. If the blood pressure does not fall within normal limits, the second step is initiated, and an antihypertensive drug is prescribed.

Other drugs are added, if needed, to keep the blood pressure consistently within normal limits. Patients with more severe hypertension often require more than two drugs to attain control. The third step is to add additional drugs. The dose of each drug is increased as needed to achieve the desired blood pressure level unless side effects occur. In the event of side effects, another drug is substituted. Newer blood pressure medications are very expensive, and cost is a concern for many patients. Some drug companies have programs to help patients who cannot afford their medications. If a potassium-wasting diuretic is prescribed, the patient is taught to increase the potassium intake. A potassium supplement is added to treatment, and electrolyte levels are monitored regularly.

Patients should monitor their blood pressure at home and keep records of the readings. Periodic visits to the physician’s office for regular examinations are necessary. The better the blood pressure is controlled and kept within normal limits, the less damage there will be to the target organs.

Complications

Malignant hypertension is a term describing rapidly progressive moderate to severe hypertension that is difficult to control. Diastolic pressure ranges from 140 to 170 mm Hg, and unless effective intervention is found, the patient may suffer eye, heart, kidney, and brain damage.

Hypertensive Crisis

Hypertensive emergency is a life-threatening situation in which the blood pressure rises higher than 180/120 mm Hg and there is indication of target organ damage. Symptoms may include severe headache, blurred vision, seizures, nausea, and change in level of consciousness. It may occur if a patient has stopped taking antihypertensive medication, or it may be secondary to another disease process such as renal stenosis. The patient is placed in the intensive care unit and treated with intravenous (IV) emergency drugs, such as IV sodium nitroprusside (Nipride), nicardipine (Cardene IV), fenoldopam (Corlopam), or labetalol (Normodyne), to lower the blood pressure. A reduction in blood pressure to 160/100 mm Hg is desired over the first 2 hours. Blood pressure is monitored every 5 to 15 minutes. Medication is adjusted to reduce the pressure slowly to prevent renal, cerebral, or coronary ischemia. Hypertensive urgency occurs when the blood pressure rises to 180/120 mm Hg but there are no signs or symptoms of target organ damage. This is the more common occurrence. The patient is observed in the emergency department and treated with oral medication. The patient is directed to follow up with the primary care physician.