Thoracic Anesthesia for the Geriatric Patient




Thoracic Anesthesia for the Geriatric Patient



Maria Castillo



Abstract


As the population ages, the number of patients of advanced age who present for thoracic surgery will steadily increase. Optimal management of these patients in the perioperative period will necessitate an understanding of changes in physiologic reserve and consideration of comorbid conditions and overall health status. Chronic obstructive pulmonary disease and congestive heart failure in particular have implications for postoperative morbidity and mortality. Patient quality of life, overall life expectancy, and functional status must also be considered.


Various studies involving preoperative assessment aim to elucidate risk factors and implement resources to optimize overall patient health and physiologic condition and thus decrease morbidity and mortality. Minimally invasive surgical techniques, extent of surgical resection, and anesthetic considerations may all play roles in achieving satisfactory outcomes in this population.


Keywords


thoracic; anesthesia; geriatric; elderly; lung resection



Introduction


Among the geriatric population, there is great variability in physiologic condition from person to person. Because of this variability, the patient’s preoperative functional status, comorbidities, and tumor stage may influence surgical outcomes more than chronologic age alone. However, even an otherwise healthy older person will exhibit limited physiologic reserve because of the normal process of aging. Optimal management of these patients in the perioperative period will necessitate an understanding of changes in physiologic reserve and consideration of comorbid conditions and overall health status. Chronic obstructive pulmonary disease (COPD) and congestive heart failure in particular have implications for postoperative morbidity and mortality. Patient quality of life, overall life expectancy, and functional status must also be considered.


Various studies involving preoperative assessment aim to elucidate risk factors and implement resources to optimize overall patient health and physiologic condition, and thus decrease morbidity and mortality. Minimally invasive surgical techniques, extent of surgical resection, and anesthetic considerations may all play roles in achieving satisfactory outcomes in this population.



Demographics


It is predicted that by the year 2030, there will be more than 70 million United States citizens over the age of 65 years.1 Adults 85 years old or older are the fastest growing age group in the United States. By 2060, the number of people aged 85 years and older is expected to nearly triple from 6.4 million in 2016 to 19 million.2


Cancer is the second leading cause of death in the United States, and the probability of developing cancer increases with age. Among people age 60 to 79 years, it is the leading cause of death.3 The incidence of cancer is 9.8 times greater among people older than 65 years than those younger than 65 years.4 According to the National Cancer Institute Surveillance, Epidemiology, and End Results (SEER) Program, 56% of all new cancer diagnoses were among patients older than 65 years.1 Almost two-thirds of cancer survivors are aged 65 years or older.5 People older than 85 years make up 2% of the population, but 8% of all new cancer diagnoses.2 It is estimated that there were 228,150 new diagnoses of cancer of the lung or bronchus, and 142,670 deaths from these cancers in 2019. Lung cancer is the most common cause of cancer death, compromising 25% of all cancer deaths. It is the second most common cancer diagnosis for both men and women.3 The median age of lung cancer patients presenting for surgery is greater than 70 years.6


The expanding geriatric population, with its increased risk of cancer compared with younger patients, will lead to an increase in elderly patients presenting for thoracic surgery. Thoracic anesthesiologists must be adept at caring for patients who may have a wide range of chronic conditions, as well as suffer from expected age-related physiologic changes.



Physiology of Aging


Elderly patients may exhibit a limited ability to respond to the stress of illness or major surgery because of the natural decline of maximal physiologic reserves. Manifestations of pathology may be blunted, and a geriatric patient may have symptoms that are atypical, diminished, or misdiagnosed as simply because of “old age.”7 The incidence of comorbidities is increased in this patient population, especially cardiovascular disease and pulmonary disease. These comorbidities superimposed on normal senescence can make management of elderly patients more complex.



Cardiovascular Changes


Interrelated molecular and structural changes occur within the myocardium, aorta, and cardiac conduction system (Table 38.1). The breakdown of elastin and increased collagen deposition and cross-linking cause vascular stiffness, which increases impedance and peripheral vascular resistance. The aorta becomes more dilated, exhibiting decreased compliance associated with higher wall tension, as large elastic arteries become stiffer with an increase in pulse wave velocity and pulse pressure. This in turn is associated with an increase in left ventricular (LV) afterload with LV dilatation or reduced ejection fraction. Coronary arteries may develop plaques and calcified lesions, as well as fixed stenoses.8



Table 38.1































Age-Related Cardiovascular Changes
Cardiac Progressive cardiomyocyte hypertrophy

Gradual development of cardiac fibrosis


Increased collagen deposition and altered cross-linking

Increased fatty infiltration and extracellular matrix degradation capacity

Decreased myocardial reserve capacity


Decreased left ventricular (LV) function


Increased LV mass secondary to increased wall thickness and volumes


Prolonged systolic contraction and diastolic relaxation

Increased risk of conduction defectsDecreased heart rate variability
Increased stroke work

Increased dependence on preload and atrial kick


Decreased autophagy


Accumulation of misfolded proteins and dysfunctional mitochondria

Vascular Increased afterload

Increased peripheral vascular resistance

Increased incidence of coronary artery disease, plaques, calcification, and fixed stenosis
Impaired vasodilation

Decreased arterial elasticity

Aortic dilation and increased pulse wave velocity

Aortic thickening with decreased compliance and higher wall tension

Reflex regulation Decreased sympathetic signaling

Baroreceptor impairment

Decreased chronotropic and inotropic response to catecholamines
Decreased maximal cardiac output and heart rate
Diminished autonomic control of peripheral vascular resistance

Modified from Castillo MD, Port J, Heerdt PM. Thoracic surgery in the elderly. In: Slinger P, ed. Principles and Practice of Anesthesia for Thoracic Surgery. 2nd ed. Switzerland: Springer; 2019; Meschiari CA, Ero OK, Pan H, Finkel T, Lindsey ML. The impact of aging on cardiac extracellular matrix. Geroscience. 2017;39(1):7–18; Shirakabe A, Ikeda Y, Sciaretta S, Zablocki DK, Sadoshima J. Aging and autophagy in the heart. Circ Res. 2016;118(10):1563–1576.


Progressive myocyte hypertrophy, myocardial fibrosis, inflammation, valvular sclerosis, and calcification lead to increased LV mass over time and decreased compliance. Subcellular changes in myocyte calcium cycling occur that allow the ventricle to maintain tension against increased afterload,9 which can be helpful in some situations but maladaptive under other conditions, such as in the setting of tachycardia. In such a situation, delayed relaxation can impede chamber filling. Over time, there is an accumulation of misfolded proteins and dysfunctional mitochondria, as well as decreased in dysfunctional cell components removal by autophagy. Cardiac aging is characterized by the presence of hypertrophy, fibrosis, and accumulation of misfolded proteins and dysfunctional mitochondria. Autophagy may play an important role in combating the adverse effects of aging in the heart. Autophagy is a lysosome-dependent bulk degradation mechanism that is essential for intracellular protein and organelle quality control. Autophagic flux is generally decreased in aging hearts, with loss of function that develops exacerbated cardiac dysfunction that is accompanied by accumulation of misfolded proteins and dysfunctional organelles. Stimulation of autophagy generally improves cardiac function by removing accumulated misfolded proteins, dysfunctional mitochondria, and damaged deoxyribonucleic acid, thereby improving the overall cellular environment and alleviating aging-associated pathology in the heart.10 Increases in fatty infiltration, fibrosis, and amyloid content can result from altered collagen cross-linking that can increase the risk of conduction defects. Hypertrophic myocytes demand more energy and oxygen. As a result, cardiac performance may be maintained under normal circumstances, however, the diminished cardiac reserve may become apparent when the patient’s heart is subjected to increased workload or stressors.8


Homeostatic reflexes are dampened, which increases the impact of the age-related decline in cardiovascular reserve.9 Typical changes include decreased baroreceptor sensitivity, myocardial response to catecholamines, and autonomic control of peripheral vascular resistance. Maximal heart rate and cardiac output decrease as well.11



Pulmonary Changes


Alterations in lung parenchyma, the chest wall, and central regulation of respiration that occur with aging can contribute to decreased respiratory function (Table 38.2). Fewer alveoli and lung capillaries, enlargement of alveolar air spaces, and decreased airway size and alveolar-capillary surface area become apparent with age. These changes result in decreased elastic recoil and less negative ­intrapleural pressure. Weakened musculature, a stiffer rib cage, kyphosis, and a greater anteroposterior diameter of the thorax lead to decreased chest wall compliance. The pulmonary physiologic changes of the aging lung may synergize with the pathologic changes of various lung diseases to affect lung structure and function. Such synergistic effects may lead to more severe manifestations of lung disease in the elderly. Loss of elastic recoil of the lung is a prominent feature of aging, similar to asthma and COPD. The presence of alveolar enlargement in the aged adult likely coexists with destruction of alveolar walls and the inflammatory infiltrate found in patients with emphysema. Aging leads to changes in the expression of transforming growth factor-β and extracellular matrix composition, which may lead to increased incidence of fibrotic lung disorders in the elderly. Although total lung capacity is characteristically maintained with normal aging, because the increased residual volume is counterbalanced by the decrease in vital capacity, this is not the case in the older individual with fibrotic lung disease, given the significant decrease in vital capacity (Fig. 38.1).


image
• Fig. 38.1 Changes in respiratory mechanics lead to changes in lung function. The reduction in elastic recoil pressure with aging causes a decrease in forced expiratory volume in 1 second (FEV1) and forced vital capacity (FVC), and increase in functional residual capacity (FRC) and total lung capacity (TLC). The decreased elastic recoil pressure facilitates airway closure, which increases air trapping (i.e., FRC and residual volume increase). Reduced chest wall compliance and decreased respiratory muscle strength increase residual volume but tend to decrease TLC. RV, Residual volume. (From Skloot GS. The effects of aging on lung structure and function. Clin Geriatr Med. 2017;33(4):447–457.)


Table 38.2
























































Age-Related Respiratory Changes
Structural Alterations in collagen fiber network

Decreased number of alveoli

Decreased number of lung capillaries
Impairment of elastic recoil

Alveolar duct dilation

Enlargement of alveolar air spaces
Diminished alveolar-capillary surface area
Decrease in alveolar surface tension
Less efficient mucociliary transport
Diminished protective airway reflexes
Extrapulmonary Loss of respiratory muscle mass

Decreased diaphragmatic strength


Decreased chest wall compliance because of fibrosis


Stiffening of the rib cage because of calcification

Decreased negative intrapleural pressure
Central regulation Blunted ventilatory response to hypoxia
Blunted ventilatory response to hypercarbia
Increased periodic breathing during sleep
Functional manifestations Increased functional residual capacity (FRC)
Increased air trapping
Decreased forced expiratory volume exhaled in 1 sec (FEV1)
Decreased forced vital capacity (FVC)

Increased residual volume (RV)

Increased closing capacity
Decreased maximal voluntary ventilation (MVV)
Increased work of breathing
Widened alveolar-arterial gradient for oxygen
Increased dead space

Decreased diffusion capacity of the lung for carbon monoxide (DLCO)

Increased ventilation–perfusion mismatch
Decreased resting arterial partial oxygen pressure (PaO2)

More susceptible to infection and environmental stresses


Modified from Castillo MD, Port J, Heerdt PM. Thoracic surgery in the elderly. In: Slinger P, ed. Principles and Practice of Anesthesia for Thoracic Surgery. 2nd ed. Switzerland: Springer; 2019; Skloot GS. The effects of aging on lung structure and function. Clin Geriatr Med. 2017;33(4):447–457; Barnes PJ. Pulmonary diseases and ageing. Subcell Biochem. 2019;91:45–74.


Aging is associated with changes in the pulmonary circulation that occur in response to increased dead space ventilation and ventilation/perfusion mismatch, as well as to general stiffening of the pulmonary vasculature, with an increase in pulmonary arterial systolic pressure particularly pertinent during exercise. The effects on the pulmonary circulation because of aging combined with severe lung disease may worsen gas exchange and increase the work of breathing12 (Fig. 38.2).


image
• Fig. 38.2 The expiratory limb of the flow volume loop in an elderly subject (dashed line) suggests obstruction to airflow by its convex or scooped-out appearance in contrast to the flow volume loop from a younger subject (solid line). (From Skloot GS. The effects of aging on lung structure and function. Clin Geriatr Med. 2017;33(4):447–457.)

Secretory and immune function also wane, resulting in less efficient mucociliary transport, less robust polymorphonuclear leukocyte function, blunted delayed-type hypersensitivity response to foreign antigens, and an increased response to autologous antigens.11 Ventilatory response to hypoxia and hypercarbia is diminished, and periodic breathing during sleep may increase. Air trapping, work of breathing, closing capacity, dead space, and ventilation-perfusion mismatch increase. Forced expiratory volume exhaled in one second (FEV1), forced vital capacity (FVC), diffusing capacity, and maximal voluntary ventilation (MVV) decrease.12 The alveolar-arterial gradient for oxygen widens, and resting arterial oxygen partial pressure (PaO2) decreases. As a result of these changes, lung function can additionally be compromised after thoracic surgery, particularly in patients who have a history of COPD. Splinting for pain from chest incision exacerbates these effects. Conversely, opioids can further blunt the response to hypoxia and hypercarbia (Fig. 38.3).


image
• Fig. 38.3 Changes in the respiratory system with aging. (From Skloot GS. The effects of aging on lung structure and function. Clin Geriatr Med. 2017;33(4):447–457.)


Hepatorenal Changes


Changes in liver and kidney function as a result of the aging process can profoundly affect metabolism and clearance (Table 38.3). Liver size can decrease by 40%, as well as renal mass by the age of 80 years.13 Hepatic blood flow can decrease by 35% to 50%.14 Hepatic vascular resistance increases, and portal pressure increases. Hepatocyte function deteriorates, decreasing molecular biosynthesis and clearance of toxins.13 Decreased perfusion can affect the plasma clearance of drugs metabolized by the liver, such as opiates, benzodiazepines, propofol, etomidate, barbiturates, and most nondepolarizing neuromuscular blockers, which are commonly used during anesthesia.15 Decreased cytochrome P450 activity compounds this affect. Changes in immune function can predispose elderly patients to autoimmunity, while decreasing the immune response to pathogens and malignant cells.14



Table 38.3




















Age-Related Hepatorenal Changes
Hepatic Decreased number of hepatocytes

Deterioration in hepatocyte function


Reduction of liver mass and volume


Increased hepatic vascular resistance


Increased portal pressure

Decreased hepatic blood flow

Partial loss of endothelial fenestration


Increased oxidative stress


Decreased cytochrome P450 activity

Decreased molecular biosynthesis

Decreased metabolic capacity


Diminished clearance of toxins


Decreased regulation of inflammation


Impaired immune response to antigens and malignant cells


Predisposition to autoimmunity


Decreased regeneration capacity


Increased susceptibility to drug-induced liver injury


Increased susceptibility to ischemia

Renal Decreased number of functional glomeruli because of nephrosclerosis

Decreased cortical volume


Increased kidney artery atherosclerosis, arteriosclerosis


Increased tubular atrophy


Increased interstitial fibrosis

Decreased perfusion

Increased renal vascular resistanceDecreased glomerular filtration rate


Decreased functional reserve


Decreased autoregulation capacityDecreased creatinine clearance

Decreased response to antidiuretic hormone

Blunted response to aldosterone, vasopressin, and reninDecreased ability to conserve sodium or concentrate urine

Increased susceptibility to renal ischemia and renal injury

Increased risk of postoperative urinary retention and urinary tract infection


Modified from Tajiri K, Shimizu Y. Liver physiology and liver diseases in the elderly. World J Gastroenterol. 2013;19(46):8459–8467; Gekle M. Kidney and aging- a narrative review. Exp Gerontol. 2017;87(Pt B):153–155; Denic A, Glassock RJ, Rule AD. Structural and functional changes with the aging kidney. Adv Chronic Kidney Dis. 2016;23(1):19–28; Maeso-Diaz R, Ortega-Ribera M, Fernandez-Iglesias A, et al. Effects of aging on microcirculatory function and sinusoidal phenotype. Aging Cell. 2018;17(6): e12829.


The number of functional glomeruli decrease with aging as a result of increased nephrosclerosis, increased arterial atherosclerosis, tubular atrophy, and interstitial fibrosis. Cortical volume decreases, and there may be other structural changes, such as an increased number of cysts or focal scars. Elderly patients possess diminished renal functional reserve, putting them at higher risk for ischemia and acute kidney injury. Glomerular filtration rate (GFR) declines at a rate of 6.3 mL/min/1.73 m2 per decade. The lowest risk of mortality is at a GFR of more than or equal to 75 mL/min/1.73 m2 for those under 55 years but at a lower GFR of 45 to 104 mL/min/1.73 m2 for those 65 years and over.16 These patients experience prolonged elimination half-time of drugs, dependent on renal clearance. Reduced renal perfusion decreases GFR, creatinine clearance, and response to antidiuretic hormone aldosterone, renin, and vasopressin. Variability in individually calculated pharmacokinetic parameters increases with age, resulting in varying clearance of drugs across the geriatric population.17 Diminished sodium reabsorption, potassium secretion, and urine concentration ability puts the geriatric patient at higher risk of volume depletion and salt retention18 (Fig. 38.4).


image
• Fig. 38.4 Changes in the renal system with aging. A. Cortical volume declines, whereas medullary volume increases, making total kidney volume relatively stable until about 50 years of age. After which, medullary volume does not increase anymore and total kidney volume begins to decline. B. Schematic illustration of cortical and medullary volume changes with aging (From Denic A, Glassock RJ, Rule AD. Structural and functional changes with the aging kidney. Adv Chronic Kidney Dis. 2016;23(1):19–28.)


Nervous System Changes


Changes in the brain that occur with age include a decrease in the number of dendrites and synapses, leading to decreased neuronal connectivity and brain volume. Older patients are at higher risk of experiencing dementia, sleep disorders, memory problems, movement disorders, and delirium.19 Cognitive function varies greatly among the elderly in terms of reserve and baseline deficit. An association between postoperative delirium and long-term outcome, as highlighted by recent data, suggests that short-term cognitiveimpairment may reflect systemic deficits. Using a series of functional and cognitive assessments, Robinson et al. found a 44% incidence of delirium in a study of 144 patients over 50 years old, of whom more than half underwent thoracic ­surgery.20 Risk factors included increasing age, hypoalbuminemia, anemia, intraoperative hypotension, history of alcohol abuse, preexisting dementia, and impaired functional status. Delirium has been associated with increased length of hospital stay and a greater 6-month mortality.21


Medication choice and administration can have particular importance for geriatric patients. A recent study suggests that dexmedetomidine (DEX) may reduce the incidence and intensity of delirium in elderly patients after lung cancer surgery. Medical records of 346 lung cancer patients over 65 years post pulmonary resection for lung cancer were assigned to DEX or control group. Patients, care-providers, and investigators were all blinded to group assignment. DEX was administered in the preoperative and intraoperative periods. During postoperative day (POD) 1 to POD 7, delirium occurs in both groups. However, the incidence of delirium was lower in the DEX group than that in the control group, there were fewer moderate and severe delirium patients in the DEX group compared with the control group. Finally, patients in the DEX group had a shorter duration of delirium, a lower numeric pain rating scale during movement, and better sleep quality.22 Other data support the use of total intravenous anesthesia and epidural analgesia, citing an association between these techniques and a significant decrease in the number of unplanned admissions to intensive care for patients who underwent lung resection. A total of 253 out of 11,208 patients undergoing lung resection in the study period of 2 years that had an unplanned admission to intensive care in the postoperative period, were evaluated in the United Kingdom. The incidence of intensive care unit admission was 2.3% (95% confidence interval [CI], 2.0%–2.6%). Patients who had an unplanned admission to intensive care unit had a higher mortality (29.00% vs. 0.03%, P < .001), and hospital length of stay was increased (26 vs. 6 days, P < .001). Patients receiving total intravenous anesthesia [odds ratio [OR], 0.50 (95% CI, 0.34–0.70)], and patients receiving epidural analgesia (OR 0.56 (95% CI 0.41–0.78) were less likely to have an unplanned admission to intensive care after thoracic surgery.23

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Oct 6, 2021 | Posted by in ANESTHESIA | Comments Off on Thoracic Anesthesia for the Geriatric Patient
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