The change in demographics of the U.S. and world population has led to a significant shift in the age of the population and the absolute numbers of geriatric patients. Between 2005 and 2030, the percentage of individuals over 65 years of age is expected to increase from 12% to 20% of the U.S. population. This is an increase of almost 30 million: from 37 million to over 70 million individuals. The “oldest old” age group, over 80 years of age, represents the fastest growing segment of the population. At present there are approximately 11 million, and this number is expected to increase to over 20 million in the next 20 years. The increase in population is due to the combined effect of the aging baby boomers and the increase in longevity. The average life expectancy in the United States is now estimated at 78 years old. The increase in population of older patients will place a burden on health care systems, and this will be reflected in an increase in the proportion of older patients with multiple comorbid conditions undergoing surgery and invasive procedures. Anesthesia providers must have a clear understanding of fundamental geriatric issues and the challenges inherent in caring for this segment of the population.
Why Geriatric Anesthesiology is Important
About one third of geriatric patients undergo at least one surgery with anesthesia prior to death, and this number is likely to increase given the frequent number of new procedures requiring anesthesia. In the United States, over 30% of inpatient surgeries are performed in patients older than 65 years of age, and when considering all procedures and surgeries, this increases to 50%. In addition, anesthetic and surgical morbidity and mortality rates in the elderly are also increased.
Despite multiple population studies demonstrating that advanced age predicts adverse outcomes, prediction of how well a very elderly individual patient will tolerate a surgery can be challenging. Numerous studies support surgery in the oldest old individuals, and advanced age by itself should not be considered a contraindication for surgery. A reduction in physiologic reserve associated with normal aging can be accelerated by certain disease conditions that may render older patients more vulnerable from complications and increase the risk of severe morbidity and death. Certain conditions are associated with increased risk from anesthesia and surgery and include emergency surgery, a high American Society of Anesthesiologists (ASA) physical status (classification greater than II), low functional capacity, intracavitary surgery, congestive heart failure, and trauma. Overall the presence of significant medical conditions indicated by a high ASA score is more important than chronologic age ( Box 35.1 ) ( Fig. 35.1 ). More recently, frailty has also been identified as an important predictor of postoperative outcomes. Frailty is a state of reduced physiologic reserve beyond what would be expected with normal aging, associated multisystem impairment, and subsequent diminished homeostatic reserve. Diminished cognitive function in older patients can also be an important predictor of postoperative cognitive decline and morbidity.
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Population is heterogeneous.
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Wide disparity between physiologic and chronologic age is common.
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Advancing age is associated with a steady decline in organ function.
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Preoperative reserve organ function is unknown.
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Multiple acute and chronic comorbid conditions are typical.
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Common conditions may have atypical clinical presentations.
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Emergency procedures are associated with increased mortality and morbidity rates.
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Patients often have complex medication regimens.
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Potential diminished mental capacity makes history taking difficult.
Morbidity and Mortality Rates
Morbidity and mortality rates in older patients range from 3% to 10% following noncardiac surgery. The higher mortality rate follows emergency surgery; the lower mortality rate accordingly reflects nonemergent, less invasive procedures. In a retrospective study using data from the American College of Surgeons National Surgical Quality Improvement Program database, authors found that postoperative fatality, overall morbidity, and postoperative complications all increased with age. In individuals older than 80 years of age who developed cardiovascular, pulmonary, or renal complications, mortality rate was especially high—43% in patients developing renal insufficiency, 36% with a stroke, and 36% following a myocardial infarction. These results are similar to earlier studies by Hamel and associates, who found that for elective noninvasive surgeries such as transurethral resection of the prostate (TURP), hernia repair, knee replacement, and carotid endarterectomy, the mortality rate in older patients was less than 2%. However, in patients over 80 years of age who developed one or more complications, the 30-day mortality rate was 26% versus 4% in patients without a complication. Death occurred most frequently following a cardiac arrest (88%), acute renal failure (52%), and myocardial infarction (48%). In an analysis of surgical outcomes for patients 80 years of age and older, for every year above 80 years there is an associated 5% increase in mortality rate; thus, a 90-year-old had a 50% higher risk of death compared to an 80-year-old.
Total knee and hip arthroplasty are common elective surgeries performed in elderly patients. In a retrospective study of 46,322 patients, including 12% over the age of 80 years, overall cardiac complications were relatively uncommon (<1%), but significant risk factors for a cardiac event included age over 80 years, hypertension treated with medication, and a history of cardiac disease.
Age-Related Physiologic Changes
Aging is associated with predictable decline in organ function in all body systems, which is estimated at 1% per year after the age of 40 years. This decline leads to overall reduced physiologic reserve capacity and a limited ability to respond to acute stress, for example, during surgery and anesthesia. The addition of multiple comorbid conditions further reduces reserve capacity, increasing the risks from anesthesia and surgery ( Table 35.1 ).
| Organ System | Structural Changes | Functional Changes |
|---|---|---|
| Body composition | Decreased skeletal muscle mass Increased percentage of body fat Decreased total body water | Increased storage size for lipid-soluble drugs Decreased O 2 consumption and heat production |
| Central nervous system | Loss of neural tissue Decreased number of serotonin, acetylcholine, and dopamine receptors | Reduction in cerebral blood flow Decline in memory, reasoning, perception Disturbed sleep/wake cycle |
| Cardiovascular system | LV hypertrophy and decreased compliance Increase in vascular rigidity Decreased compliance of venous vessels | Decreased parasympathetic nervous system tone Increased sympathetic neuronal activity Desensitization of β-adrenergic receptors Increase in SVR and SBP Decrease in stroke volume and cardiac output Diastolic LV dysfunction Decreased maximally attainable HR |
| Pulmonary system | Increase in central airway size Decrease in small airway diameter Decrease in elastic tissue, reorientation of elastic fibers, increased amount of collagen Decrease in respiratory muscle strength Increased chest wall stiffness Decrease in chest wall height and increase in AP diameter | Decreased respiratory center sensitivity Decreased effectiveness of coughing and swallowing Increase in lung compliance and decrease in chest wall compliance Decreased functional alveolar surface area Decrease in D lco Decrease in P i max and P e max Decrease in ERV and VC Increase in RV and FRC with no change in TLC Increase in RV/TLC and FRC/TLC ratios Increase in closing volume and closing capacity Decrease in FVC, FEV 1 , FEV 1 /VC, and FEF at low lung volumes Increased A-a gradient and decrease in Pa o 2 |
| Renal system | Loss of tissue mass Decreased perfusion | Decreased GFR Reduced ability to dilute and concentrate urine and conserve sodium Decreased drug clearance |
| Hepatic system | Decrease in tissue mass Decrease in blood flow | Possible decrease in affinity for substrate Possible decrease in intrinsic activity Decreased first-pass metabolism of some drugs |
Cardiovascular Changes
Cardiovascular functional capacity is one of the most significant factors influencing perioperative outcome in elderly patients. Aging leads to progressive stiffening and loss of compliance in the vasculature and the myocardium. This results from the collective effects of a gradual loss of elastin, increases in collagen, and damage to collagen through glycosylation and the deposition of free radicals in connective tissue. Systolic arterial blood pressure and pulse wave velocity increase, and the left ventricle faces greater impedance to outflow and subsequent myocardial hypertrophy, further reducing ventricular compliance. Diastolic dysfunction refers to the reduction of left ventricular relaxation during diastole. The impaired relaxation of the ventricle leads to a decrease in early diastolic filling. In the elderly this may be reduced as much as 50% compared to younger patients. These alterations render the older patient very dependent on adequate atrial pressures and active atrial contraction to complete diastolic filling. Preoperatively diastolic dysfunction may be underestimated because patients frequently have vague symptoms, and studies suggest that one third or more of patients with normal preoperative left ventricular function may also have diastolic dysfunction. Older patients with diastolic dysfunction may not tolerate even brief periods of atrial fibrillation and readily develop congestive heart failure in the setting of intravascular volume overload ( Fig. 35.2 ).
Aging also alters cardiovascular autonomic function. Vagal or parasympathetic tone is decreased, and at the same time there is an increase in sympathetic nerve activity and plasma levels of noradrenaline. β-Adrenergic receptors are less responsive to stimulation with a lesser increase in heart rate and less arterial and venous relaxation with direct stimulation. α-Adrenergic receptor activity appears largely preserved. The reduction in baroreflex function and overall vascular stiffening leads to more labile arterial blood pressure and predisposes elderly patients to orthostatic hypotension. This condition may be exaggerated during anesthesia, especially in intravascularly volume-depleted patients. The impaired β-adrenergic receptor responsiveness reduces an older patient’s ability to respond to an increase in demand through increased heart rate alone, and the elderly patient becomes very reliant on vascular tone and preload.
Myocardial fibrosis and fatty infiltration of pacemaker cells lead to conduction abnormalities such as sick sinus syndrome, atrial fibrillation, and frequent premature atrial contractions. The changes in the conduction system may lead to exaggerated bradycardia following the administration of opioids, such as remifentanil.
Cardiac function in the older patient is frequently compromised further by the development of cardiac disease. Cardiovascular disease occurs in over 75% of the U.S. population over the age of 75 years. The incidence of hypertension increases dramatically in older individuals and is a leading cause of congestive heart failure. Congestive heart failure is one of the most significant risk factors for death following anesthesia and surgery.
Pulmonary Changes
In the perioperative period, 40% of deaths in patients older than 65 years are due to postoperative pulmonary complications. Postoperative pneumonia can be slow to evolve but is associated with increased 30-day mortality rate as well as increased length of hospital stay. The increased susceptibility reflects both loss of physiologic reserve and a diminished immune capacity. In addition, there is often increased colonization of the upper respiratory tract with gram-negative organisms.
As with other organ systems, there are certain predictable changes that occur during aging, including a reduction in respiratory muscle strength, a decrease in chest wall compliance, and a decrease in the elastic recoil.
With aging the chest wall becomes stiffer, and at the same time muscle strength is diminished, leading to an increase in the work of breathing. The aging chest is more barrel-shaped, and the diaphragm can become flattened, negatively impacting chest wall dynamics. The combined impact of these changes can lead to diaphragmatic fatigue and a predisposition to respiratory failure in the postoperative period and difficulty weaning from a ventilator, especially in frail older patients. Pulmonary changes with aging are similar to those that occur with smoking-induced emphysema. They both have increased size of central airways and anatomic-physiologic dead space. The lack of elastic recoil in smaller airways can result in air-trapping with positive-pressure ventilation. Closing capacity is increased, and by the age of 65 years it exceeds functional residual capacity (FRC), leading to closure of small airways and increase in shunt fraction, predisposing older patients to hypoxemia.
In addition to structural changes with the lungs, alveolar gas exchange is also impacted by an age-related increase in ventilation-perfusion mismatch, decreased diffusing capacity, and an increase in dead space. There is a gradual decrease in resting arterial oxygen tension, leaving the older patient vulnerable to the development of significant hypoxemia with even minimal residual weakness or sedation.
Respiratory-related central nervous system changes also occur, leading to a decrease in hypoxemic and hypercapnic ventilatory drive by 50% or more. The elderly patient has an increased susceptibility to narcotic-induced apnea, potentially leading to hypoxemia and hypercapnia.
Metabolic and Renal Changes
Metabolic and renal changes lead to significant changes in pharmacokinetics of anesthetic and analgesic drugs. Overall there is a decrease in the total body water and an increase in percentage of body fat, accompanied by a reduction of protein and muscle mass. Both plasma volume and intracellular water decline by 20% to 30% by the age of 75 years. Then the initial volume of distribution and plasma concentration of an anesthetic drug increase. This can have important hemodynamic consequences. For example, following the administration of propofol, older patients have an exaggerated and prolonged hypotensive reaction. This is due to the combined effect of a higher initial plasma concentration and probably to an age-related delay in the redistribution of propofol from the central compartment. These and other age-related changes have led to the broad recommendation to reduce the initial drug dose and increase the intervals between boluses in elderly patients. As total body water declines, the percentage of fat increases, which can lead to increases in drug deposition of lipid-soluble drugs and delayed elimination.
Renal changes include a 20% to 25% decrease in renal cortical mass by the age of 80 years that may be exacerbated by comorbid conditions such as hypertension and diabetes mellitus. Other renal changes include a decrease in renal blood flow with the number of functioning glomeruli and remaining glomeruli exhibiting an increase in sclerosis. There is a progressive reduction in glomerular filtration rate (GFR), from an average of 125 mL/min in a young adult to only 60 mL/min by age 80 years. As aging leads to significant reduction in muscle mass, the serum creatinine in the older patient will not accurately reflect the degree of renal insufficiency in the geriatric patient.
Several changes predispose the older patient to fluid and electrolyte abnormalities. These changes include a reduction in tubular function and limited ability to concentrate urine appropriately and a reduction in the renin-angiotensin system and the secretion of antidiuretic hormone (ADH). As a result, older patients are more likely to develop hyponatremia (e.g., in combination with diuretics) and hypernatremia (e.g., with reduced thirst perception). Renal failure accounts for 20% of all perioperative deaths, and acute renal failure in elderly patients in the postoperative period has a significant mortality rate.
Hepatic blood flow decreases and the sizes of the liver and enzyme systems decrease in elderly patients. Both qualitative and quantitative reductions in protein binding occur, potentially leading to an increase in free fraction of protein-bound drugs. Owing to the significant hepatic reserve, the impact on metabolism is less than on other systems, and hepatic aging has less clinical impact compared to age-related changes in renal function ( Fig. 35.3 ).
Changes in Basal Metabolic Rate
Metabolic rate and the effectiveness of peripheral vasoconstriction decrease in the elderly, making it more difficult for them to maintain body temperature during surgery and anesthesia. Hypothermia can lead to significant negative effects such as slowed metabolism of medications, shivering with subsequent increased oxygen demand, and potential myocardial ischemia, as well as impaired coagulation. Active warming is an important component for most patients, especially for geriatric patients undergoing procedures.
Central Nervous System Changes
A gradual decrease in brain size occurs in aging, most likely secondary to a decrease in neuronal size. The loss in brain size is associated with an increase in ventricular volume and widening of sulci. The number of neuroreceptors and neurotransmitters decreases even in the absence of dementia or recognized neurodegenerative diseases. The most significant declines are observed in acetylcholine and serotonin receptors in the cortex, dopamine receptors in the neostriata, and dopamine levels in the substantia nigra and neostriata. Normal aging can be accompanied by cognitive changes such as memory difficulty and a decrease in speed of processing; however, the extent of these changes among individuals is widely variable. Alzheimer disease is the most common dementia, accounting for 60% to 80% of cases, followed by vascular dementia, dementia associated with Parkinson disease, dementia with Lewy bodies, and frontotemporal dementia. The incidence of Alzheimer dementia increases significantly in aging patients and is estimated to affect 45% of people over 85 years of age. Mild cognitive impairment (MCI) may represent a precursor of Alzheimer disease. Cognitive impairment (with or without a formal dementia diagnosis) is a major risk factor for postoperative cognitive complications.
Perioperative Care in the Elderly
The preoperative evaluation (also see Chapter 13 ) in the older patient is challenging but remains an important aspect of the anesthetic. In addition to certain geriatric-specific elements described later, older patients should undergo standard risk stratification for cardiopulmonary risk prior to surgery. The 2014 American College of Cardiology/American Heart Association (ACC/AHA) Guideline on Perioperative Cardiovascular Evaluation and Management of Patients Undergoing Noncardiac Surgery provides an algorithmic approach for further cardiac testing and evaluation. Laboratory testing in older patients should be performed if clinically indicated, acknowledging that as a result of the increased number of comorbid conditions, older patients will often need more testing for surgeries and procedures in general. For the elderly patient the functional assessment is one of the most important aspects of the preoperative evaluation. Excellent medical fitness, as described by activity level, is associated with a reduction in postoperative complications. In addition, the identification of significant geriatric syndromes, such as frailty and cognitive impairment, can identify “at risk” patients and potentially direct risk-reduction strategies as well as prepare patients and caregivers more realistically about the postoperative course. As stated, routine laboratory testing should not be performed based on advanced age alone. All laboratory testing should be based on the patient’s medical history and the invasiveness of the anticipated surgery. Age-based criteria for electrocardiograms (ECGs) and other testing are no longer recommended. Instead, elderly patients with a cardiac history, hypertension, or a history of active cardiac disease may need a preoperative ECG if the surgery is more than a minimal risk and no recent ECG is available. The preoperative ECG may reveal significant abnormalities and confirm the presence of preexisting cardiac disease such as left ventricular hypertrophy and prior myocardial infarction. Comparison with a prior ECG is recommended to establish the timing of a possible cardiac event, yet preoperative abnormalities on ECGs have a low specificity for predicting postoperative complications. Furthermore, an older patient may have a normal ECG and still have significant occult cardiac dysfunction. A routine chest radiograph is not indicated preoperatively in the absence of pulmonary symptoms or abnormalities on physical examination. A chest radiograph may be indicated to assess cardiopulmonary status such as pulmonary congestion or the presence of pneumonia.
The preoperative evaluation of an elderly patient who resides in a skilled nursing facility (“nursing home”) or rehabilitation facility can be especially challenging. These patients often have significant comorbid conditions that may make the preoperative interview challenging. In addition, a separate trip to a hospital for a preoperative evaluation may not be feasible. In these patients a history and list of medications may be reviewed prior to the day of surgery and anesthesia. This approach may also be useful for patients who have cataracts and carry an intense burden of disease but are undergoing a very low risk, noninvasive procedure. For all patients with cognitive dysfunction from dementia or neurologic disease, it is important to identify the person who can provide consent for the patient as well as how that person can be reached. Although sometimes uncomfortable, a discussion of advanced health care directives can be initiated during the preoperative assessment of these patients.
Functional assessment is another important component of the preoperative evaluation. In addition to the standard preoperative questions about the patient’s past medical history, an assessment of function using activity scores, activities of daily living (ADLs), and instrumental activities of daily living (IADLs) is recommended for frail older patients ( Box 35.2 ).
a The ability of the patient to perform the listed tasks independently, partially independently, or with complete assistance required is recorded.
Malnutrition in elderly patients occurs in 13% of community dwelling elders, and increases to 39% and 50% for elders in the hospital or rehabilitation facility. Poor nutrition is associated with an increased risk of wound complications such as wound infection or anastomotic leak that increase postoperative length of stay. Recommended nutritional assessments include calculating body mass index (BMI), measuring baseline serum albumin and prealbumin levels, and inquiring about unintended weight loss in the prior 12 months. A BMI of less than 18.5 kg/m 2 , serum albumin of less than 3.0 g/dL, and a weight loss of more than 10% in 6 months indicate severe nutritional risk, and appropriate referral for supplemental nutrition may be indicated, especially for elective surgeries that can be delayed or postponed. In addition, malnutrition is a frequent indicator of overall frailty.
Frailty is characterized by a decrease in physiologic reserve across multiple systems in excess of normal age-related decline in function. The underlying cause of frailty is not totally understood, but frailty appears to be related to an inflammatory state and autonomic and immune dysregulation. Frailty impacts 7% to 10% of community dwelling elders, increasing with age to 25% in individuals over age 85 years. It appears to be particularly high in patients undergoing surgery—estimated between 25% and 56%. Frailty is independently associated with increased postoperative mortality rate, morbidity, and delirium, and all contribute to an increased length of stay, readmission, and discharge to an institution as opposed to home.
Several tools and approaches can be employed to identify frailty preoperatively. The clinical phenotype model, first described in 2001, identifies five observable conditions : unintended weight loss (>10 lb in the past year), weakness (assessed by grip strength), self-reported exhaustion, slow walking speed, and low physical activity. Robinson identified additional “traits” to characterize susceptible frail individuals undergoing colorectal surgery. These traits included (1) measures of daily function such as ADL or IADL (see Box 35.2 ), (2) a Timed Up and Go (TUG) test greater or equal to 15 seconds ( Box 35.3 ), (3) an assessment of cognitive function (e.g., the Mini-Cog test with a score < 3) ( Box 35.4 ), (4) a measure of comorbid condition burden, (5) anemia defined as hematocrit less than 35%, (6) poor nutrition assessed as an albumin level less than 3.4 g/dL, and (7) a history of falls within 6 months. Patients were considered as frail if they had four or more traits, nonfrail if they had none or one trait, and intermediate with two to three traits. Researchers found that frailty was associated with increased complications and length of stay postoperatively. In general, higher frailty scores defined using the phenotype model and adaptations are associated with poor outcomes following surgery, and frailty assessment is becoming a more accepted risk assessment tool. This is particularly valuable for older patients in whom the benefits of surgery need to be balanced with realistic expectations about postoperative complications and outcomes ( Fig. 35.4 ).
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