• Aging correlates with a physiologic decline and increase in prevalence of disease.
• Care of geriatric patients is growing in number and need and will continue to do so; it is important for the anesthesia provider to understand the accompanying physiology/pathophysiology that results with age.

• Neurologic system
  • Cerebral blood flow (CBF) and volume decrease due to a combination of reduced cerebral metabolism and cerebral vascular changes including atherosclerosis, decreased vessel wall compliance, and vessel narrowing.
  • Short-term memory, learning, and information processing decrease.
  • Temperature regulation is impaired; there is decreased autonomic vasomotor control and sensitivity to changes.
• Cardiovascular system
  • Systolic blood pressure (SBP) and diastolic blood pressure (DBP) increase due to decreased atrial and vessel elasticity (1) [A]; there is a resultant widened pulse pressure.
  • Atrial contraction becomes increasingly important due to impaired diastolic filling (2) [A].
  • Resting and maximum heart rate (HR) decrease due to a reduction in beta-adrenergic responsiveness and cardiac contractility; the general rule is maximum HR = 220–age.
  • Left ventricular end-diastolic volume (LVEDV), left ventricular end-systolic volume (LVESV), and stroke volume increase due to myocardial structural changes (contractility, hypertrophy, and enlargement).
  • Resting and exercise cardiac output (CO) remain normal due to Frank–Starling mechanisms (2) [A].
  • Valves thicken and calcify
  • Maximal oxygen consumption (VO₂) decreases due to loss of body muscle mass, vascular structural changes, and gas exchange systems (3) [A].
  • Baroreflexes become impaired due to reduced arterial compliance leading to impaired mechanical transduction of arterial pressure changes and reduced cardio-vagal neural outflow.
• Pulmonary system
  • Oxygen gas exchange is impaired due to increased ventilation/perfusion imbalances; lower PaO₂ baseline values and normal SpO₂% are seen.
  • Carbon dioxide excretion is normal
  • Hypercapnic and hypoxic respiratory responses are impaired; there is also a reduced ability to handle congestive heart failure (CHF), infection, and obstruction.
  • Total lung capacity (TLC) is normal (4) [A]; residual volume (RV) can increase by 50%; vital capacity (VC) can decrease by 50–75% due to decreased chest wall compliance combined with air trapping.
  • Functional residual capacity (FRC) increases due to stiffer, ossified thoraxes by ~3% per decade (decreased compliance, increased outward forces. Closing volume (CV), however, decreases to a greater extent and leads to airway closure, atelectasis, and V/Q shunting.
  • FEV₁ decreases by 20–40 mL/year; forced vital capacity (FVC) decreases in males >females; results in increased breathing energy expenditure (up to 20%) due to changes in small peripheral airways and reduced chest wall compliance.
  • Respiratory muscle strength, cough, and ciliary function decrease.
• Hepatic system
  • Hepatic mass and blood flow decrease due to cell loss and reduction in the number of mitochondria with a compensatory increase in hepatocyte and mitochondrial size to preserve function.
  • Drug metabolism decreases
• GI system
  • Esophageal function and emptying decrease
  • Gastric motility, acid secretions, and absorption decrease (calcium, iron, zinc, folic acid, B12)
  • Colonic muscle contraction and rectal perception decrease
• Renal system
  • Renal mass, tubular mass, renal blood flow, creatinine clearance, and glomerular filtration rate decrease (1% per year after age 30) due to atrophy of afferent and efferent arterioles, generalized sclerosis, and comorbid disease (primary renal failure, atherosclerosis).
  • Drug clearance decreases
  • Sodium, potassium, hydrogen ion concentration, and vascular volume usually have no change.
• Immunologic system
  • Risk of infection increases due to impaired immune function secondary to decreased functional competence of NK cells, granulocytes, macrophages, impaired phagocytosis and chemotaxis-impaired cytokine production, T and B cell deficits, and increased number of autoantibodies.
• Endocrine system
  • Insulin resistance increases; insulin secretion becomes impaired; FBS and cortisol remain normal.
  • Thyroid hormone regulation decreases; T4 stays normal.
  • Testosterone, estrogen, and growth hormone decrease.
• Musculoskeletal system
  • Muscle mass, strength, and power decrease
  • Bone mineral density decreases
  • The increase in weight and decrease in body water/lean body mass lead to an increase in body fat%. Fat-soluble drugs (fentanyl, benzodiazepines) have an increased volume of distribution (V_D). Water-soluble drugs (ethanol, digoxin, gentamicin) have a decreased V_D (5) [A].
• Integumentary system
  • Connective tissue elasticity, moisture, and skin sensation decrease.
  • Collagen cross-linking increases and causes tissue fragility. This increases the risk of pressure ulcers and skin breakdown.

• Brain weight: 15% decrease
• Blood volume contraction: 20–30%
• Liver volume: 24% decrease
• Renal mass: 20% decrease

• Neurologic diseases
  • Cerebrovascular accident (CVA) risk doubles each decade after age 55 (10-year probability of CVA in men is 5.9% at age 55, 13.7% at age 70, and 22.3% at age 80).
  • Dementias may be the result of genetic, autoimmune, infectious, vascular, or traumatic brain/neuronal damage. 10% of those aged 65 and older and 20% of those aged 80 and over have some form of dementia.
  • Increased incidence of glaucoma, cataracts, macular degeneration, and presbyopia. 4% of those aged 65 years and 16% of those aged 85 have visual impairment.
  • Hearing loss may cause social isolation and contribute to paranoid ideation. 20% of those aged 50 and 90% of those aged 80 have hearing loss.
• Cardiovascular diseases
  • Hypertension (HTN) is often treated with antihypertensives. These drugs can have side effects including orthostasis, urinary frequency, dehydration, and fatigue. Prevalence is 44% at age 40 and 65% at age 70.
  • Arrhythmias. Treatment with antiarrhythmic medications, anticoagulation, and implantable pacemakers (5) [A]. Prevalence is 2% at age 60 and 10% at age 80.
  • Coronary artery disease (CAD) from plaque/cholesterol buildup can decrease coronary blood flow. Symptoms include substernal chest pain (33%), dyspnea (20%), weakness, malaise, worsening CHF, syncope, arrhythmia, or confusion. Prevalence is 20% at age 55 and 30% at age 75.
  • CHF symptoms include dyspnea and chest pain. Treatments with digoxin and diuretics have anesthetic implications. Prevalence is 22% at age 60 and 70% at age 80.
  • Valvular disease from thickened and calcified valve tissue may develop. Symptoms range from asymptomatic to dyspnea to fatigue. Treatment includes anticoagulation and valvular replacement. Prevalence is 40% at age 75–85 for mild disease and 13% for severe disease.
• Pulmonary diseases
  • Obstructive sleep apnea (OSA) from blockage of the soft palate during sleep can result in increased work of the diaphragm/lungs and brief apneic episodes. Symptoms include fatigue, snoring, headaches, and HTN. Prevalence of sleep-disordered breathing is up to 30% in the elderly.
  • Chronic obstructive pulmonary disease (COPD) may result from years of smoking. Prevalence is 20–40% in those aged >65.
  • Respiratory failure from coexisting disease (pneumonia, left ventricular failure) is more likely. Increased work of breathing on top of their baseline may increase.
  • Extubation may be delayed due to decreased ventilatory responses to hypoxia and hypercarbia, maximal breathing capacity, VC, cough strength, and clearance of secretions, as well as increased air trapping and V/Q mismatch.
• Immunologic diseases
  • Cancer increases with age due to uninhibited cell growth with tumor formation and/or distant metastasis. Symptoms include weight loss, fever, chills, night sweats, and new onset back pain. Prevalence is 1% at age 50 and 4% at age 85.
  • Infectious response may be impaired.
• Endocrine diseases
  • Diabetes is associated with large and small vessel disease. Prevalence is 10% at age 50 and 20% over age 75.
• Musculoskeletal diseases
  • Osteoarthritis increases presentation to the OR for joint replacements. Prevalence increases from 27% at age 70 to 44% at age 80.
  • Osteoporosis may result in an increased incidence of fractures. Prevalence in women over 50 is 4% and 44% at 80.

• Neurologic relevance. Postoperative cognitive dysfunction (POCD) is common in the elderly. At 3 months after surgery, the incidence of POCD was 9.9% in patients >60 years old versus 2.8% for the control group.
• Cardiac relevance. Increased risk of arrhythmias, HTN, hypotension; induction time can be affected (inhalational agents can have an increased onset, and intravenous agents a decreased onset time).
• Pulmonary relevance. Increased risk of pulmonary edema, pneumonia, aspiration (impaired cough and mucociliary clearance).
• Hepatic relevance. Impaired metabolism requires a decreased dosage of induction agents (e.g., propofol and inhalational agents); results in prolonged effects of opioids, benzodiazepines, local anesthetics, and neuromuscular blocking drugs.
• Renal relevance. Low muscle mass decreases serum creatinine values. A "normal" value may be abnormal. Drug excretion may be impaired resulting in prolonged half-life (t_1/2); fluid balance may be impaired.
• GI relevance. Increased risk of aspiration due to impaired gastric emptying and esophageal motility.
• Musculoskeletal relevance. Weakness, prolonged recovery, poor mobility, increased risk of DVT, pneumonia, and decubitus ulcers.

• Respiratory Physiology
• Diabetes Mellitus
• Coronary Artery Disease

Stephen Dechter , DO

Bruce Vrooman , MD