CHAPTER 35 HYPERTENSION
Practice of Geriatrics
CHAPTER 35 HYPERTENSION
Mark Andrew Supiano, M.D.
Diagnosis and Management
In contrast to the former view that high blood pressure is an expected normal aspect of aging, it is now evident that hypertension in the elderly is a disease state that is associated with significant adverse outcomes. Accordingly, despite an overall age-associated increase in blood pressure, there is no age adjustment to normalize the threshold values defining high blood pressure in the elderly. The classification of high blood pressure outlined, for example, by the Joint National Committee on Detection, Evaluation, and Treatment of High Blood Pressure (Table 35-1) therefore applies equally to older and younger adults.1
TABLE 35-1 CLASSIFICATION OF BLOOD PRESSURE
The National Health and Nutrition Examination Survey II is one of many epidemiologic studies documenting the fact that hypertension is a prevalent condition among older people. In this survey the overall prevalence of hypertension in noninstitutionalized individuals aged 65 to 74 years was 54.3%. According to the definition of hypertension used in this study (an average of three blood pressure readings of at least 140 mmHg systolic and/or 90 mmHg diastolic, or the use of antihypertensive medication), this percentage represents the combined prevalence rate for systolic-diastolic hypertension and isolated systolic hypertension. Diastolic blood pressure appears to increase with age up to approximately the age of 60 and then decreases, while systolic blood pressure appears to increase progressively and continuously with increasing age. Isolated systolic hypertension, defined as a systolic blood pressure in excess of 160 mmHg with a diastolic blood pressure of below 90 mmHg, is identified in approximately 20% of men and 33% of women aged 80 and older.
Although common, high blood pressure in the elderly should not be considered benign; the increase in blood pressure is associated with significant morbidity (e.g., coronary heart disease, congestive heart failure, stroke, peripheral vascular disease, and renal disease) and mortality.2 It is also important to note that for any level of diastolic blood pressure, the risk of these adverse events becomes progressively greater at higher levels of systolic blood pressure.2 Therefore, the age-associated increase in systolic blood pressure is an important contributor to the morbidity and mortality associated with hypertension in the elderly.3,4
A multitude of pathophysiologic mechanisms interact in the dynamic and complex regulation of arterial blood pressure. As is the case in younger individuals, the cause of essential hypertension in older humans remains unknown. Several mechanisms that may contribute to the increase in peripheral vascular resistance, which is one pathognomonic feature of hypertension in the elderly, are listed in Table 35-2. It is important to note that while these mechanisms have not been convincingly proved to be primary age-associated changes (i.e., independent of the effects of disease or lifestyle factors), they may be important contributors to hypertension in the elderly. It is also quite possible that the age-associated increase in blood pressure is secondary to age-related disease or lifestyle factors, since there are some populations in which the increase in blood pressure with aging is either absent or less marked.
TABLE 35-2 PATHOPHYSIOLOGIC ALTERATIONS THAT MAY CONTRIBUTE TO OR ARE ASSOCIATED WITH ELEVATED BLOOD PRESSURE IN AGING
The decrease in sensitivity of the baroreflex with age (perhaps as a manifestation of the decrease in arterial distensibility) illustrates how the approach to therapy of hypertension in the elderly requires an understanding of its pathophysiologic context. The decline in baroreflex sensitivity alters the central nervous system control of sympathetic nervous system (SNS) outflow, resulting in two important manifestations. First, with an insensitive baroreflex a larger change in blood pressure is needed to activate the baroreflex and produce the appropriate compensatory response. Attenuated baroreflex sensitivity is believed to contribute to the greater blood pressure variability seen in older individuals.5 Second, attenuated baroreflex sensitivity results in enhanced SNS activity for a given level of arterial blood pressure, and this may account in part for the age-associated increase in activity of the SNS.6
In light of the greater variability in blood pressure among older individuals, making an accurate diagnosis of hypertension poses a challenge. The statement that “hypertension should not be diagnosed on the basis of a single measurement”1 is especially relevant to older patients. It has been observed that when antihypertensive medication is withdrawn from some older individuals a significant number will not have a blood pressure high enough to be classified as hypertensive. This suggests that some older people are at risk for overtreatment of their blood pressure. Careful attention to correct measurement of blood pressure (e.g., using the average of two blood pressure measurements separated by at least 2 minutes [more if there is more than a 5-mmHg difference between the first two readings] taken at three separate visits) will minimize the likelihood that older individuals will be misdiagnosed as hypertensive and inappropriately placed on an antihypertensive medication. Although there have been concerns that indirect (cuff) blood pressure measurement overestimates the actual intra-arterial blood pressure of older individuals (due to increased arterial vascular stiffness), indirect blood pressure measurement is as accurate among older people as it is in younger adults. In some individuals the true blood pressure is overestimated by the indirect method owing to incompressibility of the brachial artery, a situation referred to as pseudohypertension. There remains some uncertainty about the frequency of pseudohypertension in the elderly. The possibility of pseudohypertension should be considered in the presence of a discrepancy between the severity of the blood pressure reading and evidence of target organ damage, a wide pulse pressure, and an inadequate response to antihypertensive therapy.
Target Organ Damage and Risk Factor Assessment
Once the diagnosis of hypertension has been appropriately made, the remainder of the evaluation should be directed toward identification of target organ damage, assessment of other cardiovascular risk factors, and identification of co-morbid conditions that may influence the therapeutic decision-making process. In older hypertensive patients it may be more difficult to detect the manifestations of target organ damage that are directly attributable to elevated blood pressure in the presence of concurrent age- or disease-associated changes in organ function. The patient should be assessed for any physical signs consistent with coronary artery disease, cardiac failure, cerebrovascular disease (transient ischemic attack or stroke), or peripheral vascular diseases as well as for evidence of hypertensive retinopathy, renal insufficiency, or left ventricular hypertrophy. In addition, an evaluation to determine the presence of hyperlipidemia or diabetes mellitus and information about smoking history, dietary intake of salt and fat, alcohol intake, and level of physical activity should be obtained to aid in a determination of overall cardiovascular risk. This information is also needed to advise the patient about lifestyle modifications that may be recommended as nonpharmacologic approaches to blood pressure control. Finally, knowledge of co-morbid conditions is necessary to identify special clinical situations in which a given class of antihypertensive medication may be either recommended or contraindicated (see Table 35-3).
TABLE 35-3 POTENTIAL ADVANTAGES, DISADVANTAGES, AND SPECIAL CLINICAL CONSIDERATIONS IN THE OLDER HYPERTENSIVE RELATED TO THE MAJOR ANTIHYPERTENSIVE CLASSES RECOMMENDED FOR INITIAL TREATMENT
DIAGNOSIS AND MANAGEMENT
As is true in younger hypertensive populations, the overwhelming majority (greater than 90%) of older hypertensive patients have essential or primary hypertension. The approach to the evaluation for secondary and potentially reversible factors that may account for the increase in blood pressure in older people is similar to that recommended for younger hypertensive patients. Thus, a standard clinical evaluation consisting of a complete history and physical examination, chemistry profile (to assess electrolytes, renal function, and glucose), electrocardiogram, and chest radiograph is recommended to identify these factors. No further evaluation is normally needed unless abnormal symptoms or signs are elicited from the initial evaluation that would be consistent with renal disease (elevated serum creatinine or abnormal urinalysis), renovascular disease (e.g., presence of an abdominal bruit), hyperaldosteronism (hypokalemia), hypercortisolism (hyperglycemia, cushingoid appearance), hyperparathyroidism (hypercalcemia), or pheochromocytoma (symptoms of headache, palpitations, diaphoresis, and paroxysmal elevations of blood pressure).
Other clinical situations that might lead to an evaluation for secondary hypertension in the older patient include malignant hypertension, abrupt development of diastolic hypertension (which is unusual in light of the general decrease in diastolic blood pressure in persons older than 60 years), worsening of blood pressure control, or blood pressure that remains uncontrolled on a regimen of three antihypertensive medications. Renal disease and renovascular hypertension are the most frequent causes of secondary hypertension in the elderly; endocrinologic causes are generally less common. The only possible exception is pheochromocytoma, which, although still exceedingly rare (an overall incidence of less than 1% among patients with hypertension), may increase progressively in incidence with age.
General Approach to Therapy
There is now no question that a significant reduction in cardiovascular and cerebrovascular morbidity and mortality results from treatment to reduce blood pressure in older hypertensive patients. Epidemiologic studies have documented the fact that a significant relationship exists between the level of systolic and diastolic blood pressure and cardiovascular morbidity and mortality in the elderly.2 It is therefore inappropriate to view hypertension in the elderly as benign or a characteristic of normal aging.7
Additional support for this point of view is derived from the results of many randomized controlled trials of antihypertensive therapy in older populations. Results from a meta-analysis of six randomized controlled studies (plus three others that did not include a placebo control group), confirm that treatment of hypertension in older people is associated with significant benefits: The treatment group had significant reductions in all-cause mortality (odds ratio 0.88; 95% confidence interval [CI], 0.80 to 0.97), stroke mortality (0.64; CI, 0.49 to 0.82), and morbidity (0.65; CI, 0.55 to 0.76), as well as cardiac mortality (0.75; CI, 0.64 to 0.88) and morbidity (0.85; CI, 0.73 to 0.99).8 The Systolic Hypertension in the Elderly Program (SHEP) is unique among the studies included in this meta-analysis in its focus on isolated systolic hypertension.9 The results of the SHEP study provided the first evidence that antihypertensive drug treatment in older patients with isolated systolic hypertension could be accomplished safely and that treatment resulted in a significant (36%) reduction in the incidence of fatal and nonfatal stroke.9
Although these studies have convincingly demonstrated the benefits of antihypertensive therapy in the elderly, it is important to tailor the goals of antihypertensive therapy to a given older individual. To this end, the benefits as well as the potential risks of any therapeutic intervention should be balanced to achieve the overall goal of preventing the morbidity and mortality associated with high blood pressure without adversely affecting the patient’s functional performance or quality of life. A therapeutic approach directed toward reduction of systolic blood pressure to 135 to 140 mmHg and diastolic blood pressure to 85 to 90 mmHg should be developed using the treatments least likely to produce adverse effects (Fig. 35-1). It is important not to overtreat with an intervention that produces an excessive reduction in blood pressure. It is also unnecessary and perhaps deleterious to attempt rapid reductions in blood pressure to achieve this target level of control. In light of the age-associated pathophysiologic changes that result in impaired blood pressure homeostasis, too rapid a reduction in blood pressure may be associated with development of symptomatic hypotension in some situations (e.g., postural or postprandial hypotension). Likewise, it is advisable not to make dosage adjustments or additions of other therapies too rapidly to avoid overtreatment. Once the patient’s blood pressure has been controlled to an optimal level, it is appropriate to reevaluate the need for continued therapy. A reduction in dose or, in some cases, a trial period without antihypertensive medication (with close monitoring of the patient’s home and office blood pressure) will help to minimize the possibility of overtreatment of blood pressure.
Figure 35-1 General approach to antihypertensive therapy for mild to moderate (stage 1 or 2) hypertension in the elderly.
Another general approach to therapy is to assess the patient continuously for the development of treatment-related adverse effects as well as the response to therapy. The development of orthostatic hypotension is an adverse effect that may occur with any antihypertensive medication, although centrally acting agents and vasodilators are more commonly implicated in this regard. The symptoms of orthostatic hypotension may be atypical; rather than eliciting a history of postural unsteadiness, the older patient may cite generalized weakness or fatigue. Since orthostatic hypotension is common in hypertensive patients (its frequency increasing in parallel with the systolic blood pressure level) and its presenting symptoms are often occult, it is imperative to determine the supine and upright blood pressure measurements as part of the routine monitoring of all older hypertensive patients.
Nonpharmacologic Treatment Modalities
There are several reasons to review the role of nonpharmacologic treatment modalities first in discussing treatment of hypertension in the elderly. These modalities may be effective initial therapy for patients with mild to moderate (stage 1 or 2, see Table 35-1) hypertension as well as adjuncts in combination with pharmacologic treatments. Nonpharmacologic treatments may result in concurrent improvements in other cardiovascular risk factors and are associated with minimal risks. The older hypertensive population may in general be characterized as overweight, sedentary, and salt-sensitive. Lifestyle modifications targeted toward these characteristics may therefore be of particular benefit in older hypertensive patients. Weight reduction is recommended for hypertensive individuals who are more than 10% above their ideal body weight; weight loss on the order of 5 kg has been shown to result in small (generally less than 5 mmHg) but significant decreases in blood pressure.10 The antihypertensive effects of lower extremity aerobic exercise programs are probably additive.11 Although special considerations apply to older hypertensive patients with regard to screening for the presence of underlying cardiovascular disease and paying attention to the prevention of injuries, the safety and efficacy of aerobic exercise have been demonstrated in studies of older hypertensive individuals.12 Given the increased prevalence of salt sensitivity of blood pressure among older hypertensive patients, it follows that dietary sodium restriction may be an especially effective nonpharmacologic treatment in this population.
Overview of Pharmacologic Treatments
If a 6-month trial of nonpharmacologic treatment fails to produce the desired reduction in blood pressure in patients with mild to moderate or isolated systolic hypertension (refer to definitions in Table 35-1), pharmacologic therapy should be initiated while nonpharmacologic treatments are continued (see Fig. 35-1). Older patients who present initially with more severe hypertension (stage 3 or 4)1 almost always require pharmacologic treatment to achieve blood pressure control, and in such patients pharmacologic therapy should be initiated concurrently with nonpharmacologic methods. Since diuretics and beta-antagonists are the only agents that have been documented to decrease morbidity and mortality in clinical trials, the Joint National Committee has advised that one of these classes should be chosen as the initial agent for the treatment of simple hypertension in the absence of conditions in which their use may be relatively contraindicated.1
Each of the antihypertensive drug classes has been shown to be effective in reducing blood pressure in the older patient population; in this respect there is no universally preferred agent. Therefore, selection of a particular antihypertensive drug must be an individualized decision for each patient, taking into account the drug’s potential advantages and disadvantages (see Table 35-3 and Table 35-4). Recently, some reports have suggested the possibility of increased mortality in hypertensive patients who were treated with shorter-acting calcium channel antagonists; for this reason, long-acting calcium channel antagonists are recommended for treating hypertension. Neither direct vasodilators (e.g., hydralazine) nor central- (e.g., clonidine, methyldopa) or peripheral-acting (e.g., reserpine) adrenergic drugs are recommended for initial therapy. Furthermore, these drug classes are usually considered second-line agents in older hypertensives owing to their greater predisposition to develop adverse side effects related to these drugs (e.g., postural hypotension, reflex tachycardia, and CNS effects of sedation, lethargy, or depression). The starting dose of the initially selected agent should be reduced, and dose titration should be done more gradually in older hypertensive patients (see Table 35-4). If the target blood pressure goal is not obtained at the maximal dose of the initial agent following several months of treatment, either the drug may be switched to a drug from an alternate class or a second drug from another class may be added.
TABLE 35-4 ADMINISTRATION OF INITIAL ANTIHYPERTENSIVE AGENTS
Patient Adherence and Resistant Hypertension
Effective management of hypertension in an older person requires an approach that will promote the patient’s adherence to his or her long-term treatment. The role of patient education cannot be overlooked in ensuring that the patient understands the goals of the therapeutic program and the importance of adhering to this program. The interdisciplinary geriatric team (including, for example, nurses, dietitians, pharmacists, and social workers) is well suited to promoting this approach. There are several specific methods that will enhance adherence to the long-term medical therapy of patients with this condition. These include written information describing the specific treatment and an agreed-upon blood pressure goal, a simpler once-daily regimen, and the use of calendar or pill-box systems. Blood pressure self-monitoring by the patient is another approach that can involve the patient in the management of hypertension and perhaps enhance adherence to therapy.
In patients in whom adequate control of blood pressure fails to occur (i.e., fails to reach a target of 140/90) despite the use of three antihypertensive medications at maximum doses, evaluation for the causes of resistant hypertension should be undertaken. This evaluation should include an assessment of the patient’s adherence to the medical therapy, a review focused on potential drug interactions (e.g., nonsteroidal anti-inflammatory agents, corticosteroids, sympathomimetics, and alcohol), and an assessment for volume overload. Other possible explanations to be considered in patients with resistant hypertension are the presence of a secondary cause (renovascular hypertension in particular) or pseudohypertension.
Special Clinical Situations
HYPERTENSIVE URGENCIES AND EMERGENCIES
Hypertensive urgencies and emergencies are defined by the need to reduce blood pressure quickly to prevent target organ damage, not by an absolute blood pressure level. Elevated blood pressure in itself without symptoms or signs of target organ damage does not usually require aggressive therapy. Aggressive blood pressure reduction in a patient who presents with incidentally noted elevated blood pressure is inappropriate in the absence of a true urgency or emergency. It is of particular importance to obtain an accurate blood pressure measurement to avoid overdiagnosis of a hypertensive emergency when none is present (e.g., to consider the possibility of pseudohypertension). Complications such as orthostatic hypotension or coronary or cerebral hypoperfusion syndromes may result from too aggressive treatment of an elderly patient with elevated blood pressure.
Hypertensive urgencies are more common than true hypertensive emergencies.13 They are defined as situations in which blood pressure should be lowered within 24 hours to prevent the risk of target organ damage, such as accelerated or malignant hypertension without symptoms or evidence of ongoing target organ damage.1 The majority of these situations can be managed with oral administration of antihypertensive medications (e.g., nifedipine, clonidine, labetalol, or captopril) but generally require a hospitalized setting for frequent blood pressure monitoring. Since no additional benefit has been noted with the use of sublingual administration of any of these agents, and their more rapid onset of action may produce a deleterious reduction in blood pressure unpredictably, the oral dosage forms, which are effective within 15 to 30 minutes, are recommended.
Examples of true hypertensive emergencies in older patients include hypertensive encephalopathy, intracranial hemorrhage, acute heart failure with pulmonary edema, dissecting aortic aneurysm, and unstable angina. These situations present with symptoms and signs of vascular compromise of the affected organs: brain (symptoms of severe headache, altered vision, altered mental status, and severe hypertensive retinopathy including papilledema or focal neurologic signs), heart (symptoms and signs of left ventricular failure or angina), or kidney (presenting as acute renal failure). The goal of treatment in these emergent clinical situations is immediate reduction in blood pressure, although again not necessarily to a normal level. Management of these conditions usually requires an acute care hospital setting to permit parenteral administration of an antihypertensive agent (e.g., nitroprusside) and continuous blood pressure monitoring. In addition, for patients with evidence of fluid overload, parenteral loop diuretics may aid in achieving blood pressure control. Once the hypertensive emergency or urgency has been managed, the next steps are an evaluation to determine the reason for the increase in blood pressure (i.e., a work-up for secondary causes) and development of a plan to achieve effective blood pressure control with appropriate close patient follow-up and monitoring.
HYPERTENSION IN NURSING HOME RESIDENTS
Very little information is available about the unique management of hypertension in residents of nursing homes. This is unfortunate given the prevalence of this condition among this population. While there is perhaps no major difference in the approach to the nursing home patient with hypertension, special considerations are warranted with respect to making the correct diagnosis, defining the goals of therapy and the effects on quality of life in this more frail patient population, and addressing the potential for adverse effects of therapy.
The available data suggest the possibility that blood pressure measurements of nursing home residents obtained by nursing staff may not be accurate; in one study hypertension was misclassified in 20% of nursing home residents.14 Consideration should be paid to the goals of antihypertensive therapy in this population. The presence of other conditions that limit a patient’s life expectancy may dictate a less aggressive approach to treatment of the elevated blood pressure. This benefit-risk approach should also incorporate the probability of adverse effects of antihypertensive therapy in this population. Since one of the most important risk factors for an adverse drug reaction is the total number of medications prescribed, any addition to the list of drugs given a nursing home resident increases the possibility of an adverse drug reaction. Nursing home residents, on average, experience two falls a year, and falls are a major source of morbidity in this population. Therefore, it is imperative that orthostatic blood pressure be carefully monitored in this population to attempt to minimize medication-induced orthostatic hypotension as a causal factor of falls.
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