Physiologic Changes of Aging

Physiologic changes of aging affect virtually every organ system and have many effects on the health and functional status of elders (Table 182-1). Heart disease is the leading cause of hospitalization and death.⁵ Increased peripheral vascular resistance with aging leads to an increased risk of hypertension. Decreased inotropic and chronotropic cardiac functioning compromises the patient’s ability to respond to physiologic stressors. Atherosclerosis is common and contributes not only to the rate of heart disease but also to the risk of vascular conditions (e.g., stroke, mesenteric ischemia, peripheral vascular disease, aortic dissection, and abdominal aortic aneurysm).

Because of several changes that occur with aging, elders are at higher risk for infections. Prostate disease in men and incomplete bladder emptying in women with pelvic floor abnormalities predispose to urinary tract infections. Microaspiration increases the risk of pneumonia, and fragile, aging skin prone to injury and breakdown increases the risk of infections of the skin and soft tissues. Immunosenescence of cell-mediated immunity predisposes patients to reactivation of latent diseases (e.g., tuberculosis) and may be associated with increased susceptibility to neoplasms. Cancer is the second most common cause of hospitalization and death in older patients.⁵

Fractures are the fifth leading cause of hospitalization, reflecting the high rate of osteoporosis, particularly in women.⁴ Arthritis is the most prevalent outpatient disease in elders because of the wear on cartilaginous joints, particularly of the knees, hips, and hands.⁴ Arthritis greatly affects quality of life, and these patients report fair or poor health approximately three times more often than patients without arthritis do.

Although the physiology of aging often affects a patient’s functional status, laboratory values are usually within the normal range. Abnormal laboratory values in elders should be evaluated as abnormal findings and should not be attributed to “normal effects of aging.”

Pharmacologic Considerations

Polypharmacy, drug interactions, and misuse and abuse of medications in elders are crucial health care issues. Elders currently consume more than 30% of the prescription drugs in the United States, and this figure is projected to increase to 50% by 2020. More than 40% of elders use five or more drugs weekly, and more than 10% use ten or more.6,7

Although multiple medications may be necessary to treat the medical problems that occur with aging, significant adverse health effects may result. Underlying medical problems, multiple physicians, changing pharmacokinetics of aging, and treatment of side effects of one medication with another drug are all contributory. Twelve percent to 30% of admitted elders have adverse drug reactions or interactions as a primary or major contributing factor to their admission, and 25% of these drug reactions or interactions are serious or life-threatening.6,7

Pharmacokinetics may change with age. Altered gastrointestinal motility and blood flow, decreased lean body mass, increased proportion of adipose tissue, decreased creatinine clearance, and decreased hepatic blood flow may alter the absorption, distribution, and clearance of medications. Despite these changes, the bioavailability of most medications is not significantly altered in elders. Medication interactions and side effects pose significant problems, however, particularly because many elders take multiple medications. Emergency physicians may unwittingly contribute to this problem by adding a new medication at discharge that may have an adverse drug interaction with a patient’s preexisting medications. In addition, the altered pharmacokinetics in elders necessitates caution when medications are administered in the ED, particularly sedative-hypnotics and narcotics. For these agents, a good rule of thumb is “start low and go slow.”

Several medications frequently used in the outpatient elder population are considered to be “potentially inappropriate medications.” This list includes but is not limited to narcotic analgesics, nonsteroidal anti-inflammatory agents, sedative-hypnotics, muscle relaxants, and antihistamines.8–10 These agents are generally not recommended for use in this population of patients and should be used sparingly.

The medications most often implicated in adverse reactions in elders in the ambulatory setting are cardiovascular medications, followed by diuretics, nonopioid analgesics, hypoglycemics, and anticoagulants.11,12 Caution should be used in prescribing any of these classes as they can contribute to morbidity and mortality in this age group.

The various analgesic medications used in the elderly can cause a wide range of adverse reactions and interactions. Narcotics and sedative-hypnotic agents can decrease cognition and increase the risk of falls and accidents. Nonsteroidal anti-inflammatory drugs (NSAIDs) may have serious and potentially lethal side effects. The toxicity of NSAIDs includes azotemia, worsened hypertension, and congestive heart failure as a result of sodium retention. Gastrointestinal toxicity ranges from bleeding to perforation.¹³ The data support use of extreme caution in prescribing NSAIDs. These complications can be seen in patients taking widely available over-the-counter formulations of these drugs. The significant increase in cardiovascular risk with the use of cyclooxygenase 2 inhibitors has led to a dramatic decrease in the use of these agents.

Because of these concerns, pain management in the elderly can pose a challenge. Although a “first, do no harm” philosophy is laudable, treatment of pain is one of the most important remedies physicians have to offer. Three major considerations influence the choice of medication for elderly patients. First, chronic pain (e.g., arthritis pain) may require treatment different from that of an acute painful condition (e.g., wrist fracture). Second, the patient’s underlying medical problems, social situation, and baseline functional status need to be considered.¹⁴ Third, starting with low doses, then titrating upward to effect, is the safest strategy.

Overall, acetaminophen has the highest safety profile in elders and often is the drug of choice for chronic painful conditions (e.g., degenerative joint disease). Although inadvertent excessive dosing can occur, acetaminophen is safe and should be considered first-line management for chronic pain and acute conditions causing mild to moderate pain.

NSAIDs effectively ease pain, but these agents have a ceiling analgesic effect. Increasing the dose increases the risk of side effects without increasing the analgesic benefit. These agents in low doses should be used as second-line agents after acetaminophen in chronic or acute painful conditions.

Narcotics may be necessary for acutely painful conditions and chronic conditions refractory to acetaminophen or NSAIDs. The common side effect of constipation can be a problem, and older patients need to be instructed to exercise regularly, to eat high-fiber foods or supplements, and to remain well hydrated. Because these agents may decrease cognition, start with low doses and titrate upward as needed, and patients and their families should be told of the increased risk of falls associated with these agents.