If it seems as though you spend a lot of time administering antihypertensives to your patients, it’s probably because you do. About 30% of Americans and as many as 60% of hospitalized patients have hypertension. Show
And they aren’t the only big numbers. At least a hundred antihypertensives from six drug classes are available, and many patients need some combination of these drugs to control their hypertension. That presents a real challenge for nurses who need to know the actions, adverse effects, nursing considerations, and patient teaching points for all these drugs. Defining hypertensionHypertension is called the silent killer because many people have it but don’t know they do until complications develop. To aid early detection, the Joint National Committee on the Prevention, Detection, Evaluation, and Treatment of High Blood Pressure created a prehypertension category. (See Prehypertension and hypertension: By the numbers.) The American Heart Association defines hypertension as any of the following:
Types of hypertensionThe two major types of hypertension are primary (also called essential) and secondary. Primary hypertension, or hypertension without a known cause, accounts for more than 90% of hypertension diagnoses. Major risk factors for primary hypertension are related to lifestyle and family history or genetics. Fortunately, people can change their lifestyle, and an awareness of a family history or genetic tendency can help motivate them to do so. The condition is more common and more severe in non-Hispanic blacks, elderly people, and obese people. The goal of therapy for primary hypertension is control, not cure. Secondary hypertension results from conditions such as kidney disease, thyroid disease, pheochromocytoma, preeclampsia, and obstructive sleep disorder. If the condition is successfully treated, the hypertension resolves. Other types of hypertension include isolated systolic hypertension (ISH), resistant hypertension (RH), and white-coat hypertension (WCH). More common in the elderly, ISH is a condition in which only the systolic blood pressure is elevated. Age and obesity are associated with RH, defined as high blood pressure that persists despite therapy with three antihypertensives from different classes including a diuretic. A person whose blood pressure rises when measured by a healthcare professional has WCH. Regardless of the type, a hypertensive patient needs therapy. For every 20/10 mm Hg increase in blood pressure above 115/75 mm Hg, the risk of cardiovascular disease doubles. Blood pressure regulationBlood pressure regulation depends on these factors:
All hypertensive therapy focuses on one or more of these factors, whose physiology involves a complex interplay of the renin-angiotensin-aldosterone system (RAAS), hormones of the sympathetic nervous system, peripheral autoregulatory components, vascular endothelial mechanisms, and fluid and electrolytes. Treatment begins with lifestyle changes, such as losing weight, exercising, stopping smoking, making dietary changes, and reducing stress. However, if these measures aren’t enough to control hypertension, healthcare providers turn to antihypertensives. These drugs fall into six classes: diuretics, adrenergic blockers, calcium channel blockers, drugs acting on the RAAS, direct vascular dilators, and central adrenergic agonists. Each of the six classes uses a distinct mechanism to achieve the same result, and each class has its own potential adverse effects. DiureticsDiuretics are the first-line therapy for hypertension. When a diuretic alone can’t control the condition, a prescriber adds one or more other types of antihypertensives until the blood pressure is under control. Diuretics work by eliminating excess salt and water from the body, thus decreasing the pressure from fluid on the vessel walls. The most common types of diuretics are potassium-sparing, loop, and thiazide. Prescribers often order a thiazide diuretic such as hydrochlorothiazide because these older drugs are not only effective but also relatively inexpensive. The major adverse effects of diuretics are dehydration and electrolyte imbalance. Nursing considerations
Adrenergic blockersAdrenergic blockers interfere with the sympathetic nervous system hormones that produce the fight-or-flight response, a response that increases blood flow to the heart, lungs, skeletal muscles, and brain. When stimulated, beta1 receptors in the heart increase heart rate and contractility, thus increasing cardiac output. Beta blockers, such as atenolol and metoprolol, selectively affect the beta1 receptors in the heart, preventing increases in heart rate and contractility. Because they decrease the work of the heart, beta blockers protect it from ischemia and the damaging effects of hypertrophy and remodeling. Another type of adrenergic receptor, alpha receptors, when stimulated, cause vasoconstriction of peripheral blood vessels, thus shunting blood to the heart, lungs, skeletal muscles, and brain. Alpha blockers, such as doxazosin and prazosin, inhibit this effect, resulting in vasodilation of the peripheral vessels and reduced blood pressure. A combination of an alpha and beta blocker, such as carvedilol and labetalol, can be prescribed to decrease cardiac output and increase peripheral vasodilation. Nursing considerationsFor beta-blocker therapy
For alpha-blocker therapy
Calcium channel blockersThe two types of calcium channel blockers are dihydropyridines and nondihydropyridines. Dihydropyridines, such as amlodipine and nifedipine, cause vasodilation of the peripheral blood vessels and the coronary arteries but no reduction in heart rate. These drugs may cause severe vasodilation, resulting in dizziness, and a reflex sympathetic discharge, causing tachycardia, flushing, and
headache—reactions that can be dangerous in patients who have coronary artery disease and are prone to angina. To decrease the chances of sudden Nondihydropyridines, such as diltiazem and verapamil, block the slow calcium channels in the heart and reduce heart rate and cardiac output, thus reducing blood pressure. The key adverse effects are bradycardia and heart block. These drugs also have a negative inotropic effect and can precipitate heart failure in patients who have preexisting abnormalities. Nursing considerations
Drugs acting on the RAASThe RAAS is the most powerful and complex hormonal component of blood pressure control. Three types of drugs lower blood pressure by inhibiting the RAAS: ACE inhibitors, angiotensin II receptor blockers (ARBs), and renin inhibitors. (See Understanding the renin-angiotensin-aldosterone system.) ACE inhibitors interfere with the final step in the conversion of angiotensin I to angiotensin II, which works as a potent vasoconstrictor and stimulates aldosterone secretion from the adrenal cortex. Aldosterone, in turn, increases reabsorption of sodium and water by the kidneys. Angiotensin II increases myocardial and vascular endothelial remodeling, producing harmful cardiovascular effects. Studies show reduced morbidity and mortality for patients with heart failure who take ACE inhibitors. For patients with heart disease, therapy with ACE inhibitors or ARBs and beta blockers is considered best practice. Angiotensin has 2 receptors, type 1 and type 2. ARBs block the receptor for type 1 and thus inhibit vasoconstriction, aldosterone and antidiuretic hormone secretion, sodium and water retention, sympathetic nervous system stimulation, and cellular growth. ARBs don’t block receptors for type 2, which provides beneficial effects, including vasodilation, differentiation and development of tissues, and prevention of overgrowth and hypertrophy. Renin inhibitors block the ability of renin to convert angiotensinogen to angiotensin I, thus stopping angiotensin II production early in the process. Drugs that interfere with the RAAS not only lower blood pressure but also inhibit vascular hyperplasia and cardiac-muscle remodeling that occur in response to injury from chronic hypertension and myocardial infarction. These drugs are thought to be most beneficial for younger patients and white patients, who tend to have a more active renin system. Still, elderly patients and nonwhite patients receive the cardioprotective effects of these drugs. Nursing considerations
Direct vascular dilatorsDirect vascular dilators, such as hydralazine and minoxidil, relax the smooth muscle in the arterial walls. Because they don’t improve cardiovascular health and may produce certain adverse effects, they aren’t recommended as first-line drugs. Usually, they are added to the regimen when patients are resistant to diuretics, RAAS blockers, calcium channel blockers, and beta blockers. Because direct vascular dilators work exclusively by decreasing vascular resistance, they can cause a precipitous drop in blood pressure followed by baroreceptor-mediated rebound tachycardia and sodium and water retention. These effects may be more prominent with minoxidil. To prevent angina and rebound hypertension, the prescriber may add a beta blocker and a diuretic to the regimen. Nursing considerations
Central adrenergic agonistsCentral adrenergic agonists, such as clonidine and methyldopa, stimulate the alpha2-adrenergic receptors in the central nervous system and decrease blood pressure by decreasing sympathetic activity. The drugs’ effects include reduced heart rate and cardiac output and increased peripheral vasodilation. These drugs aren’t usually recommended as first-line therapy, though methyldopa may be used as a first-line drug in pregnant women because of its safety profile. Nursing considerations
Controlling hypertension safelyTo help patients tame hypertension, you must know which antihypertensives they are taking, how the drugs work, and which adverse effects they can cause. With this information, you can anticipate the plan of care and teach patients to manage their condition without adverse effects from the drugs or complications from uncontrolled hypertension. Selected referencesAmerican Heart Association. Heart Disease and Stroke Statistics—2008 update. Dallas, Texas: American Heart Association; 2008. Calhoun DA, Jones D, Textor S, et al. Resistant hypertension: diagnosis, evaluation, and treatment: a scientific statement from the American Heart Association Professional Education Committee of the Council for High Blood Pressure Research. Hypertension. 2008;51:1403-1419. Health Care Financing Administration. Acute myocardial infarction national project overview. HCFA Pub. No. 10156. 2008. http://permanent.access.gpo.gov/websites/www.hcfa.gov/quality/download/3y.pdf. Accessed May 21, 2009. Leibovitch ER. Hypertension 2008, refining our treatment. Geriatrics. 2008;63(10):14-20. National Heart Lung and Blood Institute. The Seventh Report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure. 2003. http://www.nhlbi.nih.gov/guidelines/hypertension/. Accessed May 21, 2009. Cheryl Dumont is director, nursing research and vascular access team; Jennifer Hardware is a heart center case manager. Both work at Winchester Medical Center in Winchester, Virginia. The planners and authors of this CNE activity have disclosed no relevant financial relationships with any commercial companies pertaining to this activity. |