effective against hypertension.
antihypertensive agent an agent that reduces high
blood pressure; there are many different types of drugs that do this.
diuretics inhibit the reabsorption of sodium in the renal tubules, causing an increase in urinary excretion of sodium and a decrease in the plasma volume and extracellular fluid volume. Drugs that act on adrenergic control of blood pressure include
beta-adrenergic blocking agents such as
propranolol, which act at beta-adrenergic receptors in the heart and kidneys to reduce cardiac output and renin secretion, and others such as
methyldopa that act on alpha-adrenergic mechanisms in the central or sympathetic nervous system to reduce peripheral vascular resistance.
vasodilators act directly on the arterioles to produce the same effect. Almost every case of hypertension can be controlled by one of these drugs or a combination of them. The proper combination is determined by the response of the individual patient. In some cases several drugs must be tried before the right combination is found.
Patient Education. Instruction of the patient and significant others is an essential part of antihypertensive therapy. Learning objectives are based on the patient's particular regimen of drug therapy, allowance of sodium intake, and other dietary restrictions, such as a low-calorie diet to combat obesity.
Some antihypertensive drugs can produce acute
hypotensive reactions. The patient will need to know how to prevent a hypotensive reaction and what measures to take should such a reaction occur.
Prevention of a hypotensive reaction includes avoiding hot baths and sudden immobility after exercise, both of which promote vasodilation and a lowering of arterial pressure. The patient also should be aware of the effect of sudden changes in position that can precipitate an attack of
orthostatic hypotension. Pooling of blood in the lower limbs can divert it from the brain and other vital organs. This can sometimes be avoided by moving about frequently instead of standing motionless for long periods of time. Elastic stockings also help promote venous return from the legs and help prevent fainting from decreased cerebral blood supply.
Acute hypotension can be serious, but milder hypotensive reactions with faintness and weakness can be relieved at home if the patient lies down and elevates his lower extremities above the level of his head and flexes the thigh muscles to encourage the flow of blood from his feet and legs to his brain.
The patient on a diuretic that is not potassium-sparing will need instruction on the symptoms of potassium deficit, how to avoid potassium depletion, and when to notify the doctor should hypokalemia occur.
Limitation of
sodium intake can be very confusing and emotionally stressful to the uninstructed patient. In order to comply with the prescribed restriction of sodium the patient will need to know about satisfying substitutes and alternative seasonings for food, to be aware of the necessity of reading labels carefully when buying prepared food and over-the-counter medications, and to recognize the relationship between sodium and high blood pressure and the reasons why high sodium intake is harmful to health and well-being.