ELDERLY PATIENTS

1. ELDERLY PATIENTS Drabdollahi Ref.Ch.14- basic of anestheisa

2. 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 are performed in elderly patients.

3. NORMAL PHYSIOLOGIC CHANGESWITH AGING • Functional and structural changes occur in most of the organ systems with aging. The rate of aging varies in these organ systems and is influenced by genetic factors, environment, and diet.

7. 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.

8. Aortic impedance and systemic vascular resistance increase, and there is a decrease in B-adrenergic-mediated vasodilatation of the systemic vasculature.

9. 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.

10. 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.

11. 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.

12. 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.

13. 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.

14. 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.

15. 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.

16. 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.

17. Vital capacity declines progressively with aging because of decreases in chest wall compliance, loss of lung elastic recoil, and decreases in respiratory muscle strength.

18. 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.

19. 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.

20. Renal System • The kidneys lose approximately 50% of their functional glomeruli with similar decreases in renal blood flow by 80 years 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.

21. 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.

22. 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

23. 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.

24. 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.

25. 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, and metabolism and excretion of drugs.

26. 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 . These changes may increase the level of free, unbound drug in plasma with a resulting enhanced pharmacologic effect.

28. LEAN AND FAT BODY MASS • Older individuals have decreased 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.

29. CIRCULATINGBLOOD 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 gradual decline in plasma drug concentrations and a prolonged effect of anesthetic drugs.

30. BasaLMetaboLic 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.

31. 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

32. 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. • .

33. 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 to conserve sodium and excrete potassium

34. In contrast, adrenocorticotropic hormone, cortisol, catecholamine production by the adrenal medulla, and thyroid-stimulating hormone and thyroxine levels are unchanged with aging.

35. PR-EOPERATIVE EVALUATION AND ANESTHETIC CONSIDERATIONS • The prevalence of coexisting diseases increases with aging In older individuals undergoing surgery, the most common coexisting diseases are systemic hypertension, diabetes mellitus, cardiovascular disease, pulmonary disease, neurologic disease, and renal disease.

37. 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.

38. 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.

39. 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 determine coexisting 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.

40. ELECTROCARDIOGRAM • Elderly patients with a history of coronary artery disease may benefit from a preoperative 12-lead electrocardiogram (ECG) to determine the presence and location of any previous myocardial infarction, left ventricular hypertrophy, conduction abnormalities, and ST-T wave changes indicative of ischemia. If an abnormality is present, comparison with a previous ECG is needed to determine the timing of the occurrence.

41. However, in elderly patients, abnormalities on the preoperative ECG are common and of limited value in predicting postoperative cardiac complications in no cardiac 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.

42. 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 examined to rule out preoperative congestive heart failure. However, the cost-effectiveness of routine preoperative chest radiographs in elderly patients undergoing surgery has not been defined.

43. 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.

44. 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 Jess than 110 mm Hg.

45. If systemic blood pressure is consistently elevated, optimization with appropriate antihypertensive drugs preoperatively is often recommended for elective surgery.

46. 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.

47. 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.

48. Protection from Perioperative MyocardialIschemia • Postoperative myocardial ischemia is the strongest clinical predictor of adverse postoperative cardiac events in highrisk surgical patients, with most ischemic events occurring within the first 24 hours after surgery.

49. Therefore, reducing the number and duration of perioperative ischemic events by improving the myocardial oxygen supplydemand balance during surgery may potentially improve postoperative cardiac outcomes. Reduction of myocardial metabolic oxygen demand can be achieved by perioperative administration of B-blockers to decrease myocardial contractility and heart rate.

50. 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 B-blockade as evidenced by decreased circulating levels of troponin. However, in elderly patients at low risk for ischemic heart disease, this prophylactic therapy may be potentially costly and unnecessary.