Surgery in the Geriatric Patient

Cardiovascular System

Cardiovascular disease is the leading cause of death in the United States in men and women. Of these deaths, 83% occur in persons older than 65 years old. Cardiac events account for a significant portion of the complications in older adults in the postoperative period and are attributable to disease and to changes in the structure and function of the heart that accompany aging ( Box 13.1 ). Knowledge of these changes is important in directing the postoperative management of older adults.

Morphologic changes are found in the myocardium, conducting pathways, valves, and vasculature of the heart and great vessels with increasing age. The number of myocytes declines as the collagen and elastin content increases, thereby resulting in fibrotic areas throughout the myocardium and an overall decline in ventricular compliance. Almost 90% of the autonomic tissue in the sinus node is replaced by fat and connective tissue, and fibrosis interferes with conduction in the intranodal tracts and bundle of His. These changes contribute to the high incidence of sick sinus syndrome, atrial arrhythmia, and bundle branch block. Sclerosis and calcification of the aortic valve are common but are usually of no functional significance. Progressive dilatation of all four valvular annuli is probably responsible for the multivalvular regurgitation demonstrated in healthy older persons. Finally, there is a progressive increase in rigidity and decrease in distensibility of the coronary arteries and great vessels. Changes in the peripheral vasculature contribute to increased systolic blood pressure, increased resistance to ventricular emptying, and compensatory loss of myocytes with ventricular hypertrophy.

The direct functional implications of these changes are difficult to assess accurately because age-related changes in body composition, metabolic rate, general state of fitness, and underlying disease all influence cardiac performance. It is now generally accepted that systolic function is well preserved with increasing age. Cardiac output and ejection fraction are maintained, despite the increase in afterload imposed by stiffening of the outflow tract. The mechanism whereby cardiac output is maintained during exercise, however, is somewhat different. In younger persons, output is maintained by increasing the heart rate in response to β-adrenergic stimulation. With aging, there is a relative hyposympathetic state in which the heart becomes less responsive to catecholamines, possible secondary to declining receptor function. The aging heart therefore maintains cardiac output not by increasing its rate but by increasing ventricular filling (preload). Because of the dependence on preload, even minor hypovolemia can result in significant compromise in cardiac function.

Diastolic function, however, which depends on relaxation rather than contraction, is affected by aging. Diastolic dysfunction is responsible for up to 50% of cases of heart failure in patients older than 80 years old. Myocardial relaxation is more energy dependent and therefore requires more oxygen than contraction. With aging, there is a progressive decrease in the partial pressure of oxygen. Consequently, even mild hypoxemia can result in prolonged relaxation, higher diastolic pressure, and pulmonary congestion. Because early diastolic filling is impaired, maintenance of preload becomes even more reliant on atrial kick. Loss of the atrial contribution to preload can result in further impairment of cardiac function.

It is also important to remember that the manifestation of cardiac disease in older adults may be nonspecific and atypical. Although chest pain is still the most common symptom of myocardial infarction, atypical symptoms such as shortness of breath, syncope, acute confusion, or stroke will occur in as many as 40% of older patients.

Aging also impairs blood vessel function and leads to cardiovascular disease. Vascular dysfunction is caused by (1) oxidative stress enhancement, (2) reduction of nitric oxide (NO) bioavailability, by diminished NO synthesis and/or augmented NO scavenging, (3) production of vasoconstrictor/vasodilator factor imbalances, (4) low-grade proinflammatory environment, (5) impaired angiogenesis, and (6) endothelial cell senescence. The aging process in vascular smooth muscle is characterized by (1) altered replicating potential, (2) change in cellular phenotype, (3) changes in responsiveness to contracting and relaxing mediators, and (4) changes in intracellular signaling functions. Systemic arterial hypertension is an age-dependent disorder, and almost half of the elderly human population is hypertensive. Treatment for hypertension is recommended in the elderly. Lifestyle modifications, natural compounds, and hormone therapies are useful for initial stages and as supporting treatment with medication, but evidence from clinical trials in this population is needed. Since all antihypertensive agents can lower blood pressure in the elderly, therapy should be based on its potential side effects and drug interactions.

Respiratory System

Chronic lower respiratory disease is the fourth leading cause of death after heart disease, cancer, and stroke. Respiratory problems are the most common postoperative complications in older patients ( Box 13.2 ). Both disease- and age-related changes in lung structure and function contribute to this vulnerability.

With aging, there is a decline in respiratory function that is attributable to changes in the chest wall and lungs. Chest wall compliance decreases secondary to changes in structure caused by kyphosis and is exaggerated by vertebral collapse. Calcification of the costal cartilage and contractures of the intercostal muscles result in a decline in rib mobility. Maximum inspiratory and expiratory forces decrease by as much as 50% as a result of a progressive decrease in the strength of the respiratory muscles.

In the lung, there is loss of elasticity, which leads to increased alveolar compliance with collapse of the small airways and subsequent uneven alveolar ventilation with air trapping. Uneven alveolar ventilation leads to ventilation-perfusion mismatches, which in turn causes a decline in arterial oxygen tension of approximately 0.3 or 0.4 mm Hg/yr. The partial pressure of carbon dioxide (CO ₂ ) does not change, despite an increase in dead space. This may be caused, in part, by the decline in production of CO ₂ that accompanies the falling basal metabolic rates. Air trapping is also responsible for an increase in residual volume, or the volume remaining after maximal expiration.

Loss of support of the small airways also leads to collapse during forced expiration, which limits dynamic lung volumes and flow rates. Forced vital capacity decreases by 14 to 30 mL/yr and forced expiratory volume in 1 second decreases by 23 to 32 mL/yr (in males). The overall effect of loss of elastic inward recoil of the lung is balanced somewhat by the decline in chest wall outward force. Total lung capacity therefore remains unchanged, and there is only a mild increase in resting lung volume, or functional residual capacity. Because total lung capacity remains unchanged, the increase in residual volume results in a decrease in vital capacity.

Control of ventilation is also affected by aging. Ventilatory responses to hypoxia and hypercapnia fall by 50% and 40%, respectively. The exact mechanism of this decline has not been well defined, but it may be caused by declining chemoreceptor function at the peripheral or central nervous system level.

In addition to these intrinsic changes, pulmonary function is affected by alterations in the ability of the respiratory system to protect against environmental injury and infection. Clearance of particles from the lung through the mucociliary elevator is decreased and associated with ciliary dysfunction. Many complex changes in immunity with aging contribute to increased susceptibility to infections, including a less robust immune response from both the innate and adaptive immune systems.

There is also a decrease in several components of swallowing function. Loss of the cough reflex secondary to neurologic disorders, combined with swallowing dysfunction, may predispose to aspiration. The increased frequency and severity of pneumonia in older persons have been attributed to these factors and to an increased incidence of oropharyngeal colonization with gram-negative organisms. This colonization correlates closely with comorbidity and with the ability of older patients to perform ADLs. This fact lends support to the idea that functional capacity is a crucial factor in assessing the risk for pneumonia in older patients.

Renal System

Approximately 25% of all Americans 70 years old and older have moderately or severely decreased kidney function ( Box 13.3 ). Between the ages of 25 and 85 years, there is a progressive decrease in the renal cortex. Over time, approximately 40% of the nephrons become sclerotic. The remaining functional units hypertrophy in a compensatory manner. Sclerosis of the glomeruli is accompanied by atrophy of the afferent and efferent arterioles and by a decrease in renal tubular cell number. Renal blood flow also falls by approximately 50%. Functionally, there is a decline in the glomerular filtration rate of approximately 45% by age 80 years.

Renal tubular function also declines with advancing age. The ability to conserve sodium and excrete hydrogen ion decreases, resulting in a diminished capacity to regulate fluid and acid-base balance. Dehydration becomes a particular problem because losses of sodium and water from nonrenal causes are not compensated for by the usual mechanisms. The inability to retain sodium is believed to be caused by a decline in the activity of the renin-angiotensin system. The increasing inability to concentrate the urine is related to a decline in end-organ responsiveness to antidiuretic hormone. The marked decline in the subjective feeling of thirst is also well documented but not well understood. Alterations of osmoreceptor function in the hypothalamus may be responsible for the failure to recognize thirst in spite of significant elevations in serum osmolality.

Circulating levels of erythropoietin (EPO) are higher in the healthy elderly as compared to younger individuals. Increased EPO production in the elderly is interpreted as a counterregulatory mechanism aimed at preserving normal red blood cell mass in response to a higher turnover, as well as to EPO resistance. However, EPO levels are reduced in anemic elderly individuals, suggesting an impaired counterregulatory response to low hemoglobin levels. Elderly people may develop vitamin D deficiency due to the impaired capacity of the aging kidney to convert 25-hydroxyvitamin-D to 1,25 dihydroxyvitamin-D, but extrarenal factors (i.e., 25-OH-vitamin D availability) are at least equally responsible for vitamin D insufficiency in this age group.

Because of the decline in renal function with aging, it is important to measure glomerular filtration rate in older patients as part of preoperative risk assessment and in the hospital to provide accurate medication dosing. In older hospital patients, direct measurement of creatinine clearance (CrCl) is difficult because incontinence and cognitive impairment make 24-hour urine collection unreliable. Serum creatinine level measurement may be an unreliable indicator of renal function status because this value may remain unchanged as a result of a concomitant decrease in lean body mass and, thus, a decrease in creatinine production. A serum creatinine level of 1.0 mg/dL may represent a CrCl of over 100 mL/min in a 30-year-old but less than 60 mL/min in an 85-year old.

To overcome these problems, formulas have been developed to estimate CrCl from plasma creatinine and patient characteristics. The most commonly used formulas are the Cockcroft-Gault equation and the Modification of Diet in Renal Disease equation ( Fig. 13.5 ). In a large study of older hospitalized patients, the Cockcroft-Gault equation has been shown to correlate more closely with directly measured CrCl.

Acute kidney injury (AKI) is defined as a 0.3-mg/dL or 50% or higher change in the serum creatinine level from baseline or a reduction in urine output of less than 0.5 mL/kg/h over a 6-hour interval, within a 48-hour period, and following adequate volume resuscitation. AKI is a frequent occurrence after major surgery. Up to 7.5% of patients with a normal preoperative serum creatinine level will develop AKI. AKI is associated with increased short-term morbidity and mortality, as well as increased long-term mortality. Age, in addition to emergency surgery, ischemic heart disease, and congestive heart failure, is a risk factor for the development of postoperative AKI. Furthermore, older patients with already compromised renal function are at increased risk of postoperative AKI. The keys to avoiding postoperative AKI is to understand that older patients are at increased risk and to take steps to avoid unnecessary hypovolemia and ensure proper dosing of drugs that are cleared by the kidney and of drugs that are nephrotoxic.

The lower urinary tract also changes with increasing age. In the bladder, increased collagen content leads to limited distensibility and impaired emptying. Overactivity of the detrusor muscle secondary to neurologic disorders or idiopathic causes has also been identified. In women, decreased circulating levels of estrogen and decreased tissue responsiveness to this hormone cause changes in the urethral sphincter that predispose to urinary incontinence. In men, prostatic hypertrophy impairs bladder emptying. Together, these factors lead to urinary incontinence in 10% to 15% of older persons living in the community and 50% of those in nursing homes. There is also an increased prevalence of asymptomatic bacteriuria with age, which varies from 10% to 50% depending on gender, level of activity, underlying disorders, and place of residence. Urinary tract infections alone are responsible for 30% to 50% of all cases of bacteremia in older patients. Alterations in the local environment and declining host defenses are thought to be responsible.

Hepatobiliary System

Overall, hepatic function is well preserved with aging. However, there is an increase in liver disease and in liver disease–related mortality in persons between the ages of 45 and 85 years. Morphologic changes include a reduction in overall liver weight, size, and volume. Hepatocyte size, as well as the number of binucleated cells, increases while the number of mitochondria decreases. Functionally, hepatic blood flow decreases by 35% to 50%.

The synthetic capacity of the liver, as measured by standard tests of liver function, remains unchanged ( Box 13.4 ). However, the metabolism of and sensitivity to certain types of drugs are altered. Drugs requiring microsomal oxidation (phase I reactions) before conjugation (phase II reactions) may be metabolized more slowly, whereas those requiring only conjugation may be cleared at a normal rate. Drugs that act directly on hepatocytes, such as warfarin (Coumadin), may produce the desired therapeutic effects at lower doses in older adults because of an increased sensitivity of cells to these agents. Some recent evidence has also suggested that aging may be associated with a decline in the ability of the liver to protect against the effects of oxidative stress.

The most significant correlate of altered hepatobiliary function in older adults is the increased incidence of gallstones and gallstone-related complications. Gallstone prevalence rises steadily with age, although there is variability in the absolute percentages depending on the population. Stones have been demonstrated in as many as 80% of nursing home residents older than 90 years old. Biliary tract disease is the single most common indication for abdominal surgery in older adults (see later).

Immune Function

Immune competence, like other physiologic parameters, declines with advancing age ( Box 13.5 ). This immunosenescence is characterized by enhanced susceptibility to infections, an increase in autoantibodies and monoclonal immunoglobulins, and an increase in tumorigenesis. In addition, like other physiologic systems, this decline may not be apparent in the unchallenged state. For example, there is no decline in neutrophil count with age, but the ability of the bone marrow to increase neutrophil production in response to infection may be impaired. Older patients with major infections frequently have normal white blood cell (WBC) counts, but the differential count will show a profound shift to the left, with a large proportion of immature forms.

With aging, there is a decline in the hematopoietic stem cell pool in the bone marrow that leads to decreased production of naïve T cells from the thymus and of B cells from the bone marrow. Moreover, involution of the thymus gland, with a decline in thymic hormone levels, further impairs the production and differentiation of naïve T cells and leads to an increased proportion of memory T cells. This change in the population of T cells leaves older adult hosts less able to respond to new antigens.

Some B-cell defects have recently been identified, although it is thought that the functional deficits in antibody production are related to altered T-cell regulation rather than intrinsic B-cell changes. In vitro, there is increased helper T-cell activity for nonspecific antibody production, as well as a decreased ability of suppressor T cells from old mice to recognize and suppress specific antigens from self. This is reflected in an increase in the prevalence of autoantibodies to more than 10% by 80 years of age. The mix of immunoglobulins also changes; immunoglobulin M (IgM) levels decrease, whereas IgG and IgA levels increase slightly.

Changes in the immune system with aging are similar to those seen in chronic inflammation and cancer. In addition to the reduced mitogenic responses of T cells, there is an increase in the levels of acute phase proteins. It is hypothesized that persistently elevated levels of inflammatory cytokines may be responsible for the downregulation of interleukin-2 production by chronically stimulated T cells. Markers of inflammation such as interleukin-6 have recently been shown to be increased in older patients. Chronic inflammation has been implicated in the syndrome of frailty, which is characterized by loss of muscle mass (sarcopenia), undernutrition, and impaired mobility. Inflammatory cytokines are also implicated in the normocytic anemia that is common in frail older adults.

The clinical implications of these changes are difficult to determine. When superimposed on the known immunosuppression caused by the physical and psychological stresses of surgery, insufficient immunologic responses are to be expected in older adults. The increased susceptibility to many infectious agents in the postoperative period, however, is more likely the result of a combination of stress and comorbid disease rather than physiologic decline alone.

Glucose Homeostasis

Data from the National Health and Nutrition Examination Survey have shown a clear increase in the prevalence of disorders of glucose homeostasis with age; more than 20% of persons older than 60 years old have type 2 diabetes. An additional 20% have glucose intolerance characterized by normal fasting glucose and a postchallenge glucose level higher than 140 mg/dL but less than 200 mg/dL. This glucose intolerance may be the result of a decrease in insulin secretion, increase in insulin resistance, or both ( Fig. 13.6 ).

There is now general consensus that beta cell function declines with age. This change is manifested by failure of the beta cell to adapt to the hyperglycemic milieu with an appropriate increase in insulin response. The question of insulin resistance is more controversial. Although insulin action has been shown to decrease in older adults, this change is thought to be more a function of changing body composition, with increased adipose tissue and decreased lean body mass, rather than age per se. Others believe that there is an increase in insulin resistance directly attributable to aging, as manifested by a decrease in insulin-mediated glucose uptake in muscle that is normally regulated by the glucose transporter (GLUT)-4. There is also an increase in intracellular lipid accumulation, which interferes with normal insulin signaling. These changes may be associated with the decline in mitochondrial function that also accompanies aging.

These factors, combined with comorbid illness, medications, and genetic predisposition, come together to render older surgical patients at particularly high risk for uncontrolled hyperglycemia when subjected to the usual insulin resistance that accompanies the physiologic stress of surgery. Both the endogenous glucose response to traumatic stress and glycemic response to an exogenous glucose load are exaggerated in injured older patients.

Although most of the data on glucose control and surgical outcomes are in the cardiac surgery literature, recent evidence has confirmed that uncontrolled hyperglycemia in the immediate perioperative period is associated with an increase in infections in almost all types of surgery. The optimum level of glucose control, however, is still controversial. Earlier prospective studies indicated that tight control of blood sugar (80–110 mg/dL) achieved by continuous infusion of insulin improved some outcomes, including mortality in critically ill patients in the surgical ICU, but more recent data have cast some doubt on the benefits of such strict control. In general, maintenance of the blood glucose level below 180 mg/dL in the perioperative period is now widely accepted as an appropriate target, even in older patients.

Surgical Decision-Making

Surgeons traditionally measure surgical success in terms of 30-day mortality and morbidity. For older patients, however, the definition of success is more complex. Although we are now able to perform even the most complicated surgery on our oldest patients with traditional surgical success, the quality of the outcome in the patient’s view is more likely to depend on whether he or she can continue to function as before surgery. For some older patients, losing functional independence because of a major surgical intervention may be a far worse outcome than living with, or even dying of, the disease for which surgery is offered. In a study of older patients with limited life expectancy because of serious chronic disease, Fried and colleagues examined the impact of treatment burden (low, minor interventions, such as intravenous [IV] antibiotics; high, major interventions, such as surgery) and expected outcome (desirable vs. undesirable) on patient preferences for treatment. Results indicated that more than 70% of older patients would not want even a low-burden treatment if severe functional impairment or cognitive impairment was the expected outcome. The concern for functional and cognitive impairment was more dramatic than the concern for death ( Fig. 13.2 ).

In another study of preferences for permanent nursing home placement in seriously ill hospitalized patients, 56% of patients were very unwilling or would rather die than live permanently in a nursing home. Correlation between the patient’s wishes and both the surrogate’s and physician’s opinion of the patient’s wishes was poor.

Therefore, it is essential that the older patient be given a realistic estimate of the overall functional outcome of the proposed surgical treatment, in addition to the likelihood of control or cure of the particular disease. It is also essential that the surgeon understands the patient’s preferences in the context of this broader view of surgical success. Patient’s overall goals of care and postoperative quality of life are often overlooked. As mentioned above, the new NSQIP Geriatric Surgical Calculator can be used to help older adults understand the risk of postoperative delirium and functional decline and better inform the shared decision-making.

For general and acute care surgeons, the presentation of an abdominal emergency in an older patient with multiple comorbidities presents a particularly difficult problem. When faced with the need to make a decision for surgery in a short time frame, for pathology that is potentially amenable to surgical cure, consideration is often focused entirely on the risk of short-term mortality and morbidity. This “fix it” mentality often leads down a path that neither the patient nor the surgeon intended. Several tools have been developed to help surgeons communicate more effectively with the older patient and his or her family in the acute setting. The “Best Case/Worse Case” model provides a structured way of discussing what the postoperative period will look like for the patient and has been shown to improve the quality of these difficult discussions. Another model provides a structured framework for the discussion that puts the decision-making in the context of the patient’s overall health and healthcare goals ( Box 13.6 ).

Advanced Directives

All patients should be encouraged to make a formal advanced directive and identify a surrogate decision maker should the patient become unable to make his or her own decisions. Providers should be sure to discuss the patient’s preferences directly with the patient, as discussions of these issues are not always easy and surrogates may not be fully aware of the patient’s preferences. Tools, such as “PREPARE” ( https://prepareforyourcare.org ) and the “Five Wishes” ( https://fivewishes.org ) are available to help patients and families have these discussions and create advanced care plans. Providers should also be sure when advanced directives do exist that they are clearly documented and easily accessible in the patients’ medical record.

Palliative Care

Honoring a patient’s preferences for treatment at the end of life is a necessary component of quality health care. Studies have documented that the extent of burden plays a role in patient’s decisions to choose aggressive care, and often, if the risk and benefits are appropriately discussed, aging patients may choose less aggressive treatment.

For patients with a poor prognosis, discussions regarding palliative care should happen early in the treatment conversation and do not preclude treatment of the disease or symptoms. Patients and their family members should be encouraged to complete and discuss their advanced directives, which have been shown to make decisions for care at the end of life easier for patients and their families and more in line with patient wishes. Early palliative care has been shown to lead to substantial improvements in quality of life and mood and in some studies has even been shown to have increased survival. As there has been an increased focus on the quality of care, physicians and surgeons have come to understand that treatment is not only about curing disease but also about quality of life and alleviating suffering in patients.

Cognitive Assessment

Preoperative cognitive status as a risk factor for negative postoperative outcomes in older patients is often overlooked. Cognitive assessment is rarely a part of the preoperative history and physical examination. However, preoperative cognitive deficits are common; the prevalence of dementia is approximately 1.5% at age 65 years and approximately doubles with every five additional years of life. Over one third of persons older than age 70 years have some cognitive impairment or dementia. Preexisting cognitive dysfunction can impair a patient’s capacity to give informed consent and can have significant short- and long-term consequences in the postoperative period. A history of dementia prior to surgery has been associated with increased rates of mortality and serious morbidity. Dementia is also the single greatest risk factor for postoperative delirium.

While there are several methods to assess baseline cognitive status, the Mini-Cog is an accurate test for cognitive impairment that is easy to perform in a busy clinic setting. The Mini-Cog test combines a three-item word learning and recall task (0 to 3 points; each correctly recalled word, 1 point), with a simple clock-drawing task (abnormal clock, 0 points; normal clock, 2 points, used as a distraction before word recall). Total possible Mini-Cog scores range from 0 to 5 points, with 0 to 2 suggesting high and 3 to 5 suggesting a low likelihood of cognitive impairment.

Capacity

In order to give informed consent, a patient must have decision-making capacity. The essentials of decision-making capacity are well described. In essence, the patients must be able to understand the nature of his or her illness, the risks and benefits of the treatment recommended, and the risks and benefits of the treatment alternatives. In order to be considered competent to give consent, the patient must be able to:

• 1.

  Clearly indicate a treatment choice

• 2.

  Understand the relevant information given

• 3.

  Appreciate the medical condition and the consequences of treatments

• 4.

  Reason about the treatment options

Delirium Risk

Delirium is defined as an acute disorder of cognition and attention and is among the most common and potentially devastating complications seen in older surgical patients. Delirium occurs in from 5% to over 50% of older surgical patients and is associated with longer hospital stays, increased rates of mortality, morbidity, poor functional recovery, and more discharges to locations other than home. Both cognitive dysfunction and depression are risk factors for delirium; however, other factors must also be assessed. Risk factors for delirium are divided into two groups, the preoperative or predisposing factors and the precipitating factors or those that occur in the postoperative period ( Table 13.2 ). In addition to advanced age and cognitive dysfunction, predisposing factors include functional impairment, malnutrition, comorbid illness, sensory impairment, alcohol/substance abuse, psychotropic medications, severe illness, and type of surgery. Delirium risk can be assessed using a predictive rule that considers the patient’s age, comorbidities, and type of surgery. Delirium risk can also be assessed using the ACS NSQIP Geriatric Surgical Risk Calculator described previously.

Depression

Depression is present in approximately 11% of persons older than age 71 years. Unrecognized depression in the postoperative period may explain poor oral intake, lack of participation in the postoperative treatment plan, and higher requirements for analgesics. Depression also has been associated with higher mortality and longer hospitals stays in patients undergoing cardiac surgery. Screening for depression is easily accomplished using the Patient Health Questionnaire-2, which requires the patient to answer two questions:

• 1.

  In the past 12 months, have you ever had a time when you felt sad, blue, depressed, or down for most of the time for at least 2 weeks?

• 2.

  In the past 12 months, have you ever had a time, lasting at least 2 weeks, when you did not care about the things that you usually care about or when you did not enjoy the things that you usually enjoy?

Functional Assessment

There are several ways to evaluate function in the preoperative period. Each has value in predicting outcomes of surgery.