Geriatrics and Anesthesia Practice

Chapter 49


Geriatrics and Anesthesia Practice



As a result of health care improvements and progress in overall living conditions, the number of people in the world that are 65 years and older has increased by 300% over the last 50 years. During the next decade, it is estimated that there will be a 39% increase in persons 65 years and older, bringing the number of potential patients within this age group to 55 million. For the first time in history, by the year 2050, the number of individuals 60 years of age and older will exceed the number of younger adults. In the United States (U.S.), it is projected that between 2004 and 2050 the number of older adults 65 years of age or older that are minorities will double. During this time, the population of older adults will become more racially and ethnically diverse with the number of African Americans over the age 65 years doubling, while the number of Asian American and Hispanic American will triple. Furthermore, the composition and characteristics of this population will change. The aging baby boomers (the generation born between 1946 and 1964) will have an influence on the healthcare system, because this generation will have higher levels of education, be more financially stable, be less functionally impaired, more likely to live alone, and will take more time to research anesthesia practices; therefore, anesthesia providers must continue to stay abreast of changing demographics to meet the needs of this population. This demographic shift will have significant implications for anesthesia practitioners and how they approach the surgical and anesthetic management of the geriatric patient. The purpose of this chapter is to provide a resource that reviews normal physiologic changes of the older adult and the perioperative considerations related to managing the older adult.


Definitions of aging are often subjective and place an arbitrary marker on chronologic age; however, this section will operationally define “older adults” as persons 65 years or older. Although aging is not routinely associated with surgical risk, the challenges related to anatomic and physiologic changes that occur with aging impact every aspect of the perioperative course. First, whether or not an anesthesia practitioner is willing to accept an older person as a candidate for anesthesia is one of the most important decisions providers must make. Beginning with the preoperative evaluation of the older patient, providers must understand the heterogeneity of this group, the increased variability of anesthetic response, and the diverse conditions that often occur during the aging process.1–3 However, the risk of adverse events (i.e., cognitive and functional disorders and cardiac complications) must remain key issues in the decision to proceed.


Perioperative response is difficult to foresee because of progressive decline in baseline physiologic functions, changes in American Society of Anesthesiologists (ASA) physical status classification, and age-related comorbid conditions; all of which also can impact the chance for perioperative complications. Fortunately, most anesthetics can be managed without difficulty given that the provider delivers high-quality care with constant vigilance. Perioperative complications in the older adult are directly related to negative outcomes, including morbidity and mortality in the postoperative period. Cardiac, pulmonary, and neurologic complications are the most commonly occurring postoperative complications in the elderly. Likewise, methods for studying outcome in this diverse population depend, in large part, on what is known about the underlying cause of the presenting problem. Although it is not the intent of this chapter to dictate how the practitioner should practice, every effort has been made to provide a targeted review of the changes that occur with aging and show how these changes might offer the practitioner additional evidence to be considered in their current practice, thus providing a foundation for modifying the current options to improve perioperative outcomes if required.



The Preanesthetic Evaluation


One of the basic elements of the care of surgical patients requiring anesthesia is the preanesthetic evaluation. Preanesthetic evaluation is thoroughly discussed in Chapter 19; however, the preoperative evaluation of the older adult warrants some special considerations. The preoperative evaluation in the older adult helps reduce the cost of the perioperative course and increases the quality and care in this group. The time spent conducting the preoperative evaluation is usually the anesthesia practitioner’s first introduction to the patient.


Although aging is not synonymous with increased surgical risk, progressive decline of baseline functions, age-related comorbid disease, and ASA physical status classification place older adults at greater risk for perioperative complications and death. A speedy recovery, avoidance of functional decline, and maintenance of independence postoperatively are the most important goals in the perioperative care of older adults. The greatest challenge when providing care for older high-risk surgical patients is preventing, detecting, and managing complications. Managing older high-risk patients requires vigilance and rapid and appropriate response to potential problems. Therefore, the significance of a thorough preanesthetic evaluation takes into account the body system changes; likewise, it cannot be overemphasized that pharmacokinetic and pharmacodynamic alterations that accompany aging should be taken into consideration to optimize outcomes.


Three primary factors are associated with perioperative risks in older adults: (1) reduced reserve capacity and functional decline; (2) comorbidities (atypical disease presentations); and (3) untoward reactions to medications, anesthesia, and surgery (outcomes that are difficult to predict).4,5 These risks are most often associated with age-related physiologic changes. The process of aging is responsible for both the normally accepted chronologic alterations of life and the associated increases in the chance of disease and death.



Age-Related Physiologic Changes in the Older Adult


Aging is a time-related occurrence during the life cycle of an organism and can be defined as a time-dependent biologic continuum that begins with birth and persists with gradual impairments of organ subsystems, ultimately causing any organism to become more susceptible to illness and death. By the age of 30 years, most age-related physiologic functions in humans have peaked and gradually decline thereafter. Aging is not synonymous with poor physiologic function. Because chronologic age (age in years since birth), which is often used in clinical practice, and biologic age (functional status) differ, chronologic age alone is no longer a reliable indicator of morbidity or of mortality. The degree of functional status that remains with increasing age varies. For example, a 75-year-old patient who bicycles 3 miles every day, has no evidence of coexisting diseases, and lives a healthy lifestyle is considered “physiologically young.” Whereas a 75-year-old patient who is sedentary, has a history of hypertension and diabetes mellitus, and is a chronic smoker may be deemed as “physiologically old.” In addition, changes in organ function manifest as decreased margins of reserve. Aging patients may be able to maintain homeostasis but become increasingly less able to tolerate changes, or restore homeostasis, when exposed to surgical stress, trauma, or diseases.


In the adult surgical population, it is generally accepted that the older patient has the highest risk of postoperative adverse outcomes. Postoperative adverse outcomes are primarily cardiovascular, neurologic, and pulmonary in origin.4,6,7 However, 21% of noncardiac surgical patients, age 70 years and older, will have one or more adverse postoperative events;4,8 of those older patients who experience postoperative adverse outcomes, there is a twofold risk of death within 3 months when compared with older patients who do not have adverse outcomes.8,9 Likewise, postoperative adverse outcomes dramatically increase in-hospital stay and healthcare costs.



Body Composition and Thermoregulation


Age-related changes to the body composition and its ability to thermoregulate are characterized by loss of lean body mass, increased total body fat, decreased metabolic rate, decreased total body water, and a reduction in blood volume of 20% to 30%.10 Numerous factors may contribute to the decrease in lean body mass and increased total body fat in the older person. Aging is associated with decreases in all the senses; thus, it is speculated that the decrease in smell and taste may cause foods to be less appetizing. Practitioners must be vigilant because disease and aging cause decreased lean body mass that may mimic or be confused with malnutrition. Even so, malnutrition should not be discounted in the aging patient because it may contribute to decreased albumin levels that can affect protein binding of medications. For the older adult surgical patient, decreases in caloric intake combined with illness depletes body caloric reserves necessary to withstand the stress of anesthesia and surgery. Regrettably, no clearly beneficial preoperative medication has been identified that stimulates the appetite in older adults. As a result of decrease in total body water, older adults are more vulnerable to hypotension and have difficulty compensating for positional changes.


Thermoregulation in the elderly patient is impaired. In the older adult, there is a decrease in the function of the hypothalamus. Hypothermia is more pronounced and lasts longer because of a lower basal metabolic rate, a high ratio of surface to body area mass, and less effective peripheral vasoconstriction in response to cold. It is particularly detrimental in the elderly patient because it also slows anesthetic elimination, prolongs recovery from anesthesia, impairs coagulation, and increases the chance that the patient will shiver.11 Shivering increases oxygen consumption by up to 400%, which leads to hypoxia, acidosis, and cardiac compromise. It is known that inhaled anesthetics inhibit the temperature regulating centers in the hypothalamus; thus, the aging adult has this added insult to an already inhibited hypothalamus. Thermoregulatory vasoconstriction can cause significant peripheral vasoconstriction, predisposing older adults to produce less heat per kilogram of body weight; therefore, older adults may be unable to maintain their heat in the cooler environment of the operating room. Likewise, once temperature decreases in the elderly patient, it is difficult to restore normal body temperature. Methods to maintain normothermia in the older adult patient should involve prevention of heat loss and active warming initiated in the preoperative area and continued perioperatively. Methods include the administration of all fluids and blood transfusions through a warming device, a thermal mattress or forced air warmer, and an environmental humidity higher than 50%. Age-related changes in the kinetics of medications also occur. The decrease in blood volume will produce a higher-than-anticipated initial plasma concentration when intravenous anesthetic agents are administered. This may be evident upon induction because moderate-to-severe hypotension may result. There is also a decreased volume of distribution with water-soluble medications, leading to plasma concentrations that are higher than normal. Likewise, with the increase in total body fat in older adults, fat-soluble medications have a longer half-life, possibly causing an extension of the pharmacologic properties and a slower excretion from the body.



Cardiovascular System


Age-related changes in the cardiovascular system involve structural and functional changes in the heart, vessels, and autonomic nervous system. In the older adult, the heart and vascular system is less compliant, leading to a faster propagation of the pulse pressure waveform, increase in afterload, and an increase in systolic blood pressure, leading to ventricular thickening (hypertrophy) and prolonged ejection times. The combination of ventricular hypertrophy and slower myocardial relaxation often results in late diastolic filling and diastolic dysfunction. When these changes occur, atrial contraction becomes important in the maintenance of adequate ventricular filling. Even though the elderly have higher amounts of circulating catecholamines, they exhibit decreased end-organ adrenergic responsiveness. Therefore, the older adult has a reduced capacity to increase heart rate in response to hypotension, hypovolemia, and hypoxia. Prolonged circulation time causes a faster induction time with inhalation agents but delays the onset of intravenous drugs. There is calcification of the conducting system with loss of sinoatrial node cells, which predisposes the elderly to atrial fibrillation, sick sinus syndrome, first- and second-degree heart blocks, and arrhythmias. Hence a higher proportion of this population may present with, or require, permanent pacemakers and/or automatic internal defibrillators. Calcification is not limited to the conducting system, but may be present in the valves (primarily aortic and mitral), predisposing elderly patients to valvular stenosis or regurgitation.


Hypertension is a risk factor for perioperative complications, with the risk doubling for every 20-mmHg systolic/10-mmHg diastolic increase in blood pressure. With aging, pulse pressure widens due to a greater proportionate increase in systolic blood pressure compared with diastolic blood pressure. Decreased vein compliance can lead to decreased venous return and reduced atrial filling. Likewise, there is decreased sensitivity of baroreceptors in the aortic arch and carotid sinuses in response to blood pressure changes, which results in increased episodes of hypotension. Age-related changes in the cardiovascular system of the older adult also include changes in the heart’s regulation of calcium causing the myocardium to generate force over a longer period after excitation, thereby prolonging the systolic phase of the cardiac cycle.12


The myocardium in the older adult has decreased sensitivity to beta adrenergic modulation, physiologically evident as decreased heart rate and lower cardiac dilation at the end of diastole and systole. The combined effect of decreased cardiac reserve and decreased maximum heart rate adversely affects the compensatory mechanisms of the older adult under the stress of anesthesia and surgery. Older adults undergoing noncardiac surgery are at risk of cardiovascular complication as a result of anesthesia and surgery. Although there is evidence supporting the use of beta-blockers as an effective method of reducing adverse perioperative cardiovascular events after noncardiac surgery in select high-risk surgical patient populations, this approach is currently under considerable scrutiny and debate. No matter what approach is taken, complete assessment of the cardiovascular system in the older adult undergoing noncardiac surgery is essential according to the American College of Cardiology/American Heart Association (ACC/AHA) Guidelines for Perioperative Cardiovascular Evaluation for Noncardiac Surgery. According to the ACC/AHA, functional capacity is an objective quantification of the patient’s exercise tolerance and can be measured in metabolic equivalents (METs).13 Research suggests that for every 1 MET that a patient attained, there is a corresponding reduction in annual mortality of 11%.14 The MET corresponds to the amount of oxygen consumed by a 70-kg male at rest (≈ 3 mL oxygen per kg body weight per minute). Those patients able to perform greater than 4 METs are at decreased risk for perioperative cardiac complications.


In general, older adults may have higher blood pressures caused by increased peripheral vascular resistance, decreased arterial elasticity, and cardiac workload; likewise, older adults may have decreased cardiac output and stroke volume due to decreased conduction velocity and reduction in venous blood flow. Age-related cardiovascular changes and their anesthetic implications are noted in Table 49-1. The preoperative assessment should include the identification of major risk factors for preoperative cardiovascular complications, which include significant exercise intolerance, angina, history of myocardial infarction within the past 6 months, ventricular arrhythmias, acute coronary syndrome, decompensated congestive heart failure, and valvular disease. To assist in the prediction of postoperative cardiac outcome in patients undergoing noncardiac surgery, classic preoperative cardiac risk assessment and guidelines such as the Goldman Cardiac Risk Index (GCI) may be used. The GCI applies nine independent factors to assess the level of hemodynamic stress inflicted upon the vital organs and the risk of adverse cardiac factors are assigned points accordingly (Table 49-2).




The use of beta-blockers is common in older adults with chronic heart failure, hypertension, and ischemic heart disease. However, for patients that present to the operating room who may not have had the benefit of chronic titration of this class of medication, a practical approach for the anesthesia provider might include the administration of oral medication prior to induction and intraoperative intravenous administration to control heart rate.


Cardiovascular disease is the most common concomitant illness in the older adult and the primary cause for perioperative and postoperative risk in the older adult. The most frequently associated cardiovascular coexisting diseases are hypertension, coronary artery disease, congestive heart disease (CHF), and myocardial ischemia. Myocardial infarction is the most common cardiac complication and the leading cause of death in the postoperative period. Likewise, a patient with preexisting congestive heart failure has a greater than twofold risk of developing postoperative complications.15



Respiratory System


There are various age-related alterations of the respiratory system that have an impact on oxygenation in the elderly patient. Older patients develop calcifications of the chest wall, intervertebral joints, and intercostal joints. This, along with decreased intercostal muscle mass, contributes to a decrease in chest wall compliance. In addition, there is a flattening of the diaphragm, a loss of intervertebral disc height, and changes in spinal lordosis, which may further diminish chest wall compliance. Changes also occur with the lung parenchyma. There is a generalized loss of elastic tissue recoil of the lung. Consequently, there is reduced functional alveolar surface area available for gas exchange. In elderly patients, even in the absence of disease, an increase in lung compliance impairs the matching of ventilation and perfusion, increases physiologic shunt, and results in the reduction of oxygen exchange at the alveolar level. Since lung elastic recoil is necessary for maintaining small airway caliber, an increased lung compliance causes small airway diameter to narrow, and eventually increases the closing volume (i.e., lung volume at which small airways in the dependent parts of the lung begin to close). The closing volume exceeds functional residual capacity (FRC) at approximately 65 years of age in the erect position and at age 45 years in the supine position. Other dynamic and static lung volume changes include a decrease in vital capacity (VC), an increase in residual volume (RV), and an increase in FRC with decreases in inspiratory reserve volume (IRV) and expiratory reserve volume (ERV). Total lung capacity remains unchanged or may slightly decrease due to its correlation with height. There is also a decrease in forced expiratory maneuvers. The forced vital capacity (FVC) and the forced expiratory volume in 1 second (FEV1) are both decreased due to the loss of lung elastic recoil, decrease in small airway diameter, and subsequent airway collapse with forced expiration (Figure 49-1). Overall, the elderly have impaired efficiency of gas exchange. Impaired oxygenation is reflected by a decline in resting arterial oxygen tension (Pao2), which remains somewhat stable, at approximately 83 mmHg, after 75 years of age. This decline in Pao2 is attributed to the premature closing of small airways and the reduction in the alveolar surface area.16



The regulation of breathing is also affected with aging. The central (medulla) and peripheral (carotid and aortic bodies) chemoreceptors affect ventilation with changes in pH, Pao2, and Paco2. In the elderly the ventilatory response to hypoxemia and hypercarbia is decreased, predisposing them to increased episodes of apnea. Another challenge associated with oxygenation is the progressive decrease in laryngeal and pharyngeal support that accompanies aging, which can result in airway obstruction. In addition, protective airway reflexes (i.e., coughing and swallowing) are decreased, which increases the risk for pulmonary aspiration. Age-related pulmonary changes and their anesthetic implications are noted in Table 49-3.


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May 31, 2016 | Posted by in ANESTHESIA | Comments Off on Geriatrics and Anesthesia Practice

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