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ELDERLY PATIENTS. Dr Masood EntezariAsl. Introduction. The use of health care resources, including surgical services, is disproportionately higher in the elderly than in their younger counterparts
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ELDERLY PATIENTS Dr Masood EntezariAsl
Introduction • The use of health care resources, including surgical services, is disproportionately higher in the elderly than in their younger counterparts • Many elderly patients who were denied surgical treatment in the past because of their age now routinely undergo operative procedures as a result of improvement in anesthetic, surgical, and medical care • Approximately 35% of all surgical procedures arc performed in elderly patients
NORMAL PHYSIOLOGIC CHANGESWITH AGING • Functional and structural changes occur in most of the organ systems with aging (Table) • The rate of aging varies in these organ systems and is influenced by genetic factors, environment, and diet
Cardiovascular System • Aging in healthy individuals affects the peripheral vasculature through increases in wall thickness and the diameter and vascular stiffness of the aorta and large arteries • Systolic and mean arterial blood pressure increases with widening of the pulse pressure • Aortic impedance and systemic vascular resistance increase, and there is a decrease in β-adrenergic-mediated vasodilatation of the systemic vasculature • Aging also affects the heart through increases in left ventricular wall thickness secondary to enlargement of cardiac myocytes • Myocardial compliance is decreased, with a reduction in the early diastolic filling rate and compensatory augmentation of the contribution of atrial contraction to late left ventricular filling
Ventricular diastolic dysfunction, with prolonged relaxation, should be considered in any elderly patient who has a history of decreased exercise tolerance • Despite the common belief that systolic cardiac function decreases with age, it is recognized that in the absence of coexisting cardiovascular disease, resting systolic cardiac function is well preserved, even at very advanced ages • Other cardiovascular-related changes in aging include sclerosis and calcification of the cardiac conduction system and thickening of the aortic valve cusps • Turbulent blood flow caused by thickening of the aortic valve cusps results in the midsystolic ejection murmur that is commonly present in elderly individuals • In addition, the incidence of aortic stenosis increases with aging secondary to cusp calcification because of mechanical wear and tear on the collagenous core of the valve cusp
Pulmonary System • With aging, the central airways increase in size with a resultant increase in the anatomic and physiologic dead spaces • Small airways decrease in diameter secondary to loss of connective tissue support • However, total airway resistance is unchanged, possibly because of opposite changes in the distal and proximal airways • There is a progressive loss in elastic tissue and an increase in the amount of collagen within the lung parenchyma • Lung elastic recoil and tethering support of the small airways are both reduced with consequent dilatation of respiratory bronchioles and alveolar ducts • This results in an approximately 15% reduction in the functional alveolar surface area available for gas exchange by the age of 70 years
Chest wall compliance decreases with aging • Decreased intervertebral space and age-associated kyphoscoliosis lead to decreased chest height and increased anteroposterior diameter, which may alter respiratory mechanics • Respiratory muscle strength decreases with aging secondary to multiple factors such as selective denervation of skeletal muscle fibers and atrophy and degeneration of motor nerves and muscle fibers • Static and dynamic lung volumes also undergo age related changes
The loss of elastic elements results in increasedlung compliance and residual volume • As a result, functional residual capacity (FRC) is increased, though to the lesser degree than residual volume, because the decrease in chest wall compliance in part counteracts the decrease in lung recoil • In contrast, total lung capacity decreases minimally, mainly secondary to a decrease in inspiratory muscle strength and a loss of height • Vital capacity declines progressively with aging because of decreases in chest wall compliance, loss of lung elastic recoil, and decreases in respiratory muscle strength • As a result of loss of tethering support of the small airways, closing volume and closing capacity increase
Closing capacity approaches or exceeds FRC, and the decreased ability of elderly individuals to keep the airways open during expiration and to reopen collapsed alveoli during inspiration results in an increase in ventilation-to perfusion mismatching • Although closing capacity and closing volume increase during general anesthesia, the deterioration in arterial oxygenation during general anesthesia is more related to the development of atelectasis in the dependent lung areas with the formation of a shunt, changes that have not been reported to be influenced by aging • Airway reflexes are more sluggish in elderly patients secondary to diminished laryngeal and pharyngeal responses • The cough reflex is less efficient, and the risk for pulmonary aspiration is increased
Gastrointestinal System • The swallowing and motility function of the esophagus and the gastric emptying time are usually unchanged with aging • Liver size decreases progressively with aging, and it is estimated that by the age of 80 years, liver mass is decreased by 40% with a parallel decline in hepatic blood flow • However, the content of both microsomal and nonmicrosomal liver enzymes is unchanged with aging • Liver function test results are generally normal
Renal System • The kidneys lose approximately 50% of their functional glomeruli with similar decreases in renal blood flow by 80years of age • The decline in both renal mass and renal blood flow occurs primarily in the cortex with compensatory changes in the juxtamedullary region • The glomerular filtration rate is decreased by 30% at 60 years of age and by 50% at 80 years of age • In addition, elderly individuals have a decreased ability to dilute and concentrate urine and to conserve sodium • The decrease in renal function with aging may affect the pharmacokinetics (prolonged elimination half-times) of certain drugs used in anesthesia • The overall decline in renal functional reserve usually has no effect on an elderly individual's ability to maintain extracellular fluid volume and electrolyte concentrations • Similarly, serum creatinine remains relatively stable because of a parallel decrease in overall skeletal muscle mass • However, in situations in which renal blood flow is compromised, the decreased renal functional reserve characteristic of elderly individuals may increase the risk for perioperative renal insufficiency or failure
Central Nervous System • Aging is associated with a progressive loss of neural tissue and a parallel reduction in cerebral blood flow and cerebral oxygen consumption • On average, 30% of total brain mass is lost by 80 years of age • In addition, the number of neuroreceptors generally declines with aging in various regions of the central nervous system • For example, a reduction is seen in the number of serotonin receptors in the cortex, acetylcholine receptors in multiple brain regions, and dopamine receptors in the neostriatum • Levels of dopamine in the neostriatum and substantia nigra are also decreased • These structural changes are not necessarily associated with a decline in cognitive function • However, the incidence of postoperative delirium and cognitive dysfunction is higher in elderly individuals • Patients with a history of cognitive impairment are at even higher risk for further impairment postoperatively
Pharmacokinetic and Pharmacodynamic Changes • The pharmacokinetics of drugs is influenced by changes in : - plasma protein binding - the percentage of body content that is fat or skeletal muscle (lean mass) - circulating blood volume - metabolism and excretion of drugs
PROTEIN BINDING • With aging, protein binding sites are reduced secondary to both quantitative (decreased level of circulating protein) and qualitative changes • In addition, elderly individuals frequently take multiple medications that might interfere with the binding of drugs to protein active sites (Table) • These changes may increase the level of free, unbound drug in plasma with a resulting enhanced pharmacologic effect
Drugs Often Taken by Elderly Patients That May Contribute to Adverse Effects or Drug Interactions
LEAN AND FAT BODY MASS • Older individuals havedecreased skeletal muscle mass and an increased percentage of body fat • These changes result in an increased ability to store lipid-soluble drugs, which may lead to a more gradual and prolonged release of the drugs used during anesthesia from lipid storage sites and, consequently, an increased elimination time and prolonged effect
CIRCULATING BLOOD VOLUME • Circulating blood volume generally decreases with aging and results in a higher than expected initial plasma drug concentration for the same amount of drug administered • Gradual declines in hepatic and renal function may lead to decreased metabolism and prolonged elimination of drugs and their metabolites and thus may contribute to a more gradualdecline in plasma drug concentrations and a prolonged effect of anesthetic drugs
BasaL MetaboLic Rate • The basal metabolic rate declines with aging, and elderly surgical patients may have difficulty maintaining normothermia during general anesthesia • The development of hypothermia may lead to slower metabolism and excretion of drugs in elderly patients • Furthermore, hypothermia may lead to shivering, which will increase the basal metabolic rate and oxygen consumption and result in arterial hypoxemia or myocardial ischemia, or both
Endocrine Changes • Endocrine changes occur with aging • The response of arginine vasopressin (formerly known as antidiuretic hormone) to hypovolemia and hypotension is reduced, but it remains sensitive to changes in serum osmolarity • The renal tubules are less sensitive to this hormone and atrial natriuretic peptide • During hyperglycemia, insulin release is impaired • However, because of increased peripheral tissue resistance and decreased clearance, plasma insulin levels are elevated, which results in an enlarging fat depot • Serum levels of renin and aldosterone decline, and the response of both hormones to sodium restriction and postural changes is blunted, with a decreased ability conserve sodium and excrete potassium • In contrast, adrenocorticotropic hormone, cortisol, catecholamine production by the adrenal medulla, and thyroid-stimulating hormone and thyroxine levels are unchanged with aging
The prevalence of coexisting diseases increases with aging (Table) • In older individuals undergoing surgery, the most common coexisting diseases are systemic hypertension, diabetes mellitus, cardiovascular disease, pulmonary disease, neurologic disease, and renal disease • Optimizing the patient's medical condition before surgery is essential because baseline health status is an important predictor of postoperative complications • However, for elderly patients, delaying surgery to optimize a medical condition must be weighed against the risk of delaying surgery because emergency surgical treatment is associated with higher morbidity and mortality • Furthermore, delaying certain surgical procedures, such as cancer surgery, may substantially alter the patient's prognosis • In this regard, communication among the anesthesiologist, surgeon, and primary care physician is critical to developing an optimal plan regarding the timing of each elderly patient's surgery
Laboratory Testing • Data suggest that routine laboratory testing should not be performed simply on the basis of age alone but, rather, it should be based on a thorough preoperative evaluation to determinecoexisting medical conditions and on the type of planned surgical procedures • This approach is likely to be more cost-effective than routine testing in all elderly patients
ELECTROCARDIOGRAM • Elderly patients with a history of coronary artery disease may benefit from a preoperative 12-Jead electrocardiogram (ECG) to determine the presence and location of any previous myocardial infarction, left ventricular hypertrophy, conduction abnormalities, and ST-T wave changes indicative ofischemia • If an abnormality is present, comparison with a previous ECG is needed to determine the timing of the occurrence • However, in elderly patients, abnormalities on the preoperative ECG are common and of limited value in predicting postoperative cardiac complications in noncardiac surgery • The low specificity of the preoperative ECG in predicting postoperative cardiac complications also suggests that a normal ECG does not rule out occult cardiac disease
CHEST RADIOGRAPH • In patients undergoing high-risk surgery, a chest radiograph may be useful in providing noninvasive information regarding ventricular function (cardiomegaly may indicate an ejection fraction <40%) • The pulmonary vasculature should also be examinedto rule out preoperative congestive heart failure • However, the cost-effectiveness of routine preoperative chest radiographs in elderly patients undergoing surgery has not been defined
EVALUATIONOF CARDIAC STATUS • Because the prevalence of cardiovascular disease increases with aging, evaluation of cardiac status is an integral part of the preoperative evaluation of elderly patients
Blood Pressure Control • Systemic hypertension (systolic blood pressure ≥180 mm Hg, diastolic blood pressure ≥1l0 mm Hg) increases the risk for cardiac and cerebrovascular disease • Adverse intraoperative events in hypertensive patients include perioperative myocardial ischemia, cardiac dysrhythmias, and cardiovascular lability • Although data are limited, there is little evidence of increased perioperative cardiac risk if systolic blood pressure is less than 180 mm Hg or diastolic blood pressure is less than 110 mm Hg • Even though there is no evidence that deferring anesthesia and surgery reduces peri operative risk, careful determination of the baseline blood pressure range for each patient is critical and requiresmore than one measurement preoperatively • If systemic blood pressure is consistently elevated, optimization with appropriate antihypertensive drugs preoperatively is often recommended for elective surgery
Checking compliance with blood pressure medication is important because elderly patients frequently take multiple medications, and therefore preoperative instructions on which medications to discontinue need to be carefully conveyed • In patients scheduled for urgent or emergency surgery with a preinduction systolic blood pressure higher than 180 mm Hg or diastolic blood pressure higher than 110 mm Hg, induction of anesthesia may proceed carefully, often with invasive monitoring • In these patients, administration of a small dose of an anxiolytic drug before induction of anesthesia may result in more gradual lowering of systemic blood pressure • In elderly patients with uncontrolled systemic hypertension who are about to undergo emergency surgery, the use of continuous invasive blood pressure monitoring and postoperative surveillance in the intensive care unit may be indicated
Protection from Perioperative Myocardial Ischemia • Postoperative myocardial ischemia is the strongest clinical predictor of adverse postoperative cardiac events in high risk surgical patients, with most ischemic events occurring within the first 24 hours after surgery • Therefore, reducing the number and duration of perioperative ischemic events by improving the myocardial oxygen supply demand balance during surgery may potentially improve postoperative cardiac outcomes • Reduction of myocardial metabolic oxygen demand can be achieved by perioperative administration of β-blockers to decrease myocardial contractility and heart rate • Elderly patients (≥ 65 years of age) who have one or more risk factors (systemic hypertension, current smoking, hypercholesterolemia, diabetes mellitus) may benefit from prophylactic perioperative β-blockade as evidenced by decreased circulating levels of troponin I • However, in elderly patients at low risk for ischemic heart disease, this prophylactic therapy may be potentially costly and unnecessary
Because sympathetic nervous system tone is increased with aging, administration of β-blockers during the peri operative period may result in hypotension, especially in the presence of relative hypovolemia secondary to preoperative fasting • Furthermore, autonomic control of hemodynamics in the elderly may be compromised as a result of the decrease in baroreceptor reflex activity with aging • Because perioperative tachycardia is one of the most important hemodynamic abnormalities that has been shown to be associated with myocardial ischemia, the adequacy of the heart rate response to β-blockers is critical to guide therapy • Individualized dosing of β-blockers for control of postoperative myocardial ischemia rather than a fixed-dose regimen may be more beneficial because patients with coronary artery disease have different coronary anatomy and therefore different ischemic thresholds
Physical Examination • Elderly individuals are more likely to be edentulous, and although removal of dentures preoperatively may facilitate direct laryngoscopy and tracheal intubation, positive pressure ventilation by facemask may be difficult • Range of neck motion should be evaluated because older individuals may have limitations as a result of degenerative spine disease • Auscultation of the carotid arteries over the neck bilaterally is helpful to rule out carotid artery disease but requires confirmation by carotid ultrasound if loud carotid bruits are present • Auscultation of the heart may reveal additional heart sounds such as S₃ or S₄ which are commonly associated with decreased left ventricular compliance
A midsystolic ejection murmur is often present in elderly patients secondary to thickening of the aortic cusps or calcification, or both • A laterally displaced point of maximal impulse together with increased heart size on the chest radiograph suggests cardiomegaly • Auscultation of the lungs is performed to evaluate the presence of rales or wheezes, which may be associated with congestive heart failure or lung disease (or both) • Examination of the extremities should be performed to rule out the presence of peripheral edema, which may be indicative of congestive heart failure
Risk Assessment • Although elderly patients are at increased risk for perioperative morbidity and mortality, advanced age by itself is not a contraindication to surgery • General factors that should be evaluated when performing a preoperative risk assessment include age, functional status, cognition, nutrition, and comorbid conditions (cardiac, pulmonary, renal, and endocrine disease) • When both age and comorbidity are considered, the latter is a better predictor of adverse postoperative outcomes • Functional limitation increases perioperative risk, and preoperative evaluation of functional status with common measures such as activities of daily living and instrumental activities of daily living is informative (Table) • Preoperative cognitive status has been shown to be associated with adverse postoperative outcome and functional recovery, thus emphasizing that assessment of preoperative baseline cognitive status may be useful • Depression is also common in elderly patients and may increase peri operative morbidity, including postoperative delirium
Activities of Daily Living and Instrumental Activities of Daily Living
Management of Preoperative Medication • Elderly patients are typically taking multiple prescription and over-the-counter medications • In general, all antihypertensive and cardiac medications should be continued until surgery, with the exception of diuretics, which are preferably withheld on the day of surgery because the patient will be fasting before surgery • For those taking aspirin or warfarin for treatment of cerebral vascular or coronary artery disease, atrial fibrillation, or deep vein thrombosis, the risks associated with discontinuing anticoagulation should be weighed against the benefits of reduced bleeding from discontinuation of such drugs • Warfarin is typically withheld (often four doses) to allow normalization of the international normalized ratio(INR) • In case of emergency surgery, fresh frozen plasma(FFP) or vitamin K can be administered to reverse warfarin's effects • For patients at high risk for thromboembolism, such as those with a prosthetic heart valve, a history of pulmonary embolism, or a recent history of deep vein thrombosis, a transition using low-molecular-weight heparin or intravenous heparin is indicated when oral anticoagulation is discontinued • Antibiotic prophylaxis is indicated for patients with valvular heart disease and mitral valve prolapse
No single anesthetic drug or technique has been demonstrated to be superior for elderly surgical patients • However, familiarity with the pharmacokinetics of anesthetic drugs and how age-related changes may affect drug dosing is important
Adjustments of Anesthetic and Adjuvant Drugs in Elderly Patients
Inhaled Anesthetics • The minimum alveolar concentration (MAC) for various inhaled anesthetics is reduced by approximately 6% per year after the age of 40 years • The onset of action of volatile anesthetics may be more rapid if cardiac output is reduced, particularly for more lipid-soluble drugs, butdecreased lung function secondary to an increased shunt fraction has an opposite effect • Recovery from the depressant effects of volatile anesthetics may be more prolonged because of an increased volume of distribution secondary to increased body fat and decreased pulmonary gas exchange
Intravenous Anesthetics and NeuromuscularBlocking Drugs Dose requirements for barbiturates, opioids, and benzodiazepines are likely to be decreased in elderly patients
OPIOIDS • The elimination half-time of fentanyl is longer in elderly patients than younger patients because of the larger volume of distribution • As a result, depression of ventilation and prolonged analgesia may ensue with the same dose administered to younger patients • Decreased hepatic clearance may contribute to prolonged opioid effects, especially when high does of these drugs are administered to elderly patients
PROPOFOL • Propofol is highly lipid soluble and produces rapid loss of consciousness when administered intravenously • A decreased induction dose or slow titration is recommended for elderly patients • A decrease in age-related clearance of propofol may result in reduced anesthetic requirements with aging • Propofol, because of its negative inotropic and vasodilatory effects, may give rise to exaggerated decreases in systemic blood pressure when used for induction of anesthesia in elderly patients • Despite these characteristics, propofol may be superior to thiopental for recovery of mental function
ETOMIDATE • Etomidate produces rapid loss of consciousness and has been frequently chosen for induction of anesthesia in elderly patients with cardiovascular instability • The initial volume of distribution of etomidate is decreased such that an 80-year-old patient requires less than half the dose of etomidate to produce the same magnitude of depression on the electroencephalogram as in younger patients
MIDAZOLAM • Midazolam has increased potency and decreased clearance in elderly individuals • Context-sensitive half-times are prolonged • Accordingly, doses of midazolam should be decreased and a longer duration of action is expected
NEUROMUSCULAR BLOCKING DRUGS • Despite age-related changes in the neuromuscular junction, the effects of depolarizing and nondepolarizing neuromuscular blocking drugs are not altered in elderly patients • Rather, the altered pharmacokinetics of these drugs in older individuals is secondary to decreases in renal and hepatic function and the altered volume of distribution that accompanies aging • Clearance is decreased for nondepolarizing neuromuscular blocking drugs (vecuronium, rocuronium) that are dependent on either the kidneys or the liver for elimination from plasma • The duration of action of atracurium and cisatracurium is not prolonged because these drugs are eliminated by Hofmann degradation, which is independent of renal and hepatic clearance mechanisms • Monitoring of neuromuscular function and recovery is important in elderly patients because incomplete recovery of neuromuscular function may lead to a higher incidence of postoperative pulmonary complications
Regional Anesthesia • Cardiovascular responses to either spinal or epidural anesthesia may be exaggerated in older individuals • The decrease in cardiac output is thought to primarily be due to a decrease in stroke volume • Treatment of the resultant hypotension typically consists of the administration of crystalloid solutions or vasopressors such as phenylephrine • Surgical procedures that are amenable to regional anesthesia include transurethral resection of the prostate(TURP), orthopedic procedures such as hip or knee replacement, inguinal herniorrhaphy, and minor gynecologic procedures • Technical difficulties in performing regional anesthesia probably reflect age-related decreases in the intervertebral spaces and scoliosis • A thorough examination of the targeted spinal segment must be performed before initiating regional anesthesia
Intraoperative Monitoring • Because of the prevalence of coexisting disease involving the cardiac and pulmonary systems, consideration should be given to using invasive monitoring such as arterial and central venous catheterization in elderly patients undergoing major surgical procedures, which are likely to be prolonged and include large body fluid shifts
