Elderly Patients

The elderly population, which is expected to increase by 33% over the next 2 decades, accounts for approximately 12.5% of the total U.S. population and 38% of all health care spending (approximately 5% of the U.S. gross domestic product).^[388] There are changes in the physiology, pharmacodynamics, pharmacokinetics (see Chapter 62 ), and processing of nociceptive information that may influence the effectiveness of postoperative pain control in the elderly. There may be communication, affective, cognitive, social, and ideologic barriers to effective postoperative pain control in this group. The elderly generally have decreased physiologic reserves and increased comorbidities compared with younger counterparts, which may result in a higher incidence of postoperative complications (e.g., postoperative delirium), especially in the presence of severe or uncontrolled postoperative pain.

There is a clinically significant reduction in the intensity of pain perception or symptoms with increasing age.^[389] For instance, silent myocardial ischemia is more common in the elderly, who may instead present with other anginal equivalents.^[390] Experimental studies demonstrate a decrease in Aδ and C-fiber nociceptive function, delay in central sensitization, increase in pain thresholds, and decrease in sensitivity to low-intensity noxious stimuli.^{[389] [390] [391] [392] [393]} Howoever, elderly patients may have an increased response to higher-intensity noxious stimuli, decreased pain tolerance, and decreased descending modulation (i.e., serotonin and noradrenergic), which may contribute to the relatively high incidence of chronic pain in elderly patients.^{[389] [394] [395]} Despite the methodologic

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The physiologic and pharmacokinetic effects of aging on acute pain management are complex, and the clinical implications include the slow titration of opioids that produces longer circulation times, smaller total doses because of increased sensitivity, and expectation of a longer duration of action due to reduced clearance. In general, analgesic requirements decrease with increasing age. Age has been shown to be the best predictor for postoperative requirements of intravenously and neuraxially administered morphine.^{[164] [397] [398] [399]} Similar to that seen in younger patients, there is large interpatient variability in postoperative analgesic requirements.^[397] Use of intravenous PCA in the elderly is appropriate to compensate for the wide interpatient variability, although postoperative titration of intravenous morphine can also allow successful and safe administration to elderly patients.^[400] Age per se is not an impediment to effective postoperative use of intravenous PCA or PCEA.^{[271] [398] [401]} Use of postoperative epidural analgesia for elderly patients, especially in those with decreased physiologic reserves, may attenuate perioperative pathophysiology and is reported to improve postoperative outcomes such as facilitating return of gastrointestinal function after abdominal surgery, decreasing the incidence of myocardial ischemia, lowering pain scores, and decreasing pulmonary complications.^{[167] [168] [271]}

Postoperative pain management in the elderly may be especially challenging because of some of the affective, cognitive, social, and ideologic barriers. Health care providers treating geriatric patients tend to have an unfounded level of fear of complications associated with treating perioperative pain as reflected by the inadequate treatment of pain in elderly patients, even relative to younger patients.^[395] Elderly patients may also contribute to inadequate pain control by their own reluctance to report pain or take opioid medications. Elderly patients have a higher incidence of affective or cognitive impairments (e.g., depression, dementia) that may interfere with effective pain management. ^{[395] [402]}

One of the most devastating complications in the elderly surgical patient is postoperative delirium, which is associated with increased mortality rates and longer hospital stays.^{[403] [404]} The cause of postoperative delirium is unknown, although it is believed to result from an imbalance of neurotransmitters (particularly acetylcholine and serotonin) in the presence of decreased neurophysiologic reserve and inflammatory mediators. ^{[405] [406]} Although the cause of postoperative delirium is multifactorial, uncontrolled postoperative pain may be an important contributor to its development.^[407] Higher pain scores predict a decline in mental status^[408] and an increased risk of delirium.^[409] Opioids other than meperidine^[410] have not been associated with development of postoperative delirium.^{[407] [410]} A multimodal analgesic approach may be useful in elderly patients but must be used with caution because adverse drug reactions in the elderly increase (to a greater extent than younger patients) as the number of medications administered increases.^[411] Although the benefits of intraoperative regional anesthetic techniques on postoperative cognitive function are unclear, the postoperative use of epidural analgesia may diminish postoperative delirium in part through superior analgesia and a decrease in pulmonary complications.