Diseases of Aging

Aging produces progressive accumulation of molecular damage and physiologic deterioration across all organ systems, fundamentally altering how elderly patients respond to surgical stress and anesthetic agents. The aging brain experiences cell loss and reduced neuroplasticity, diminishing cerebral perfusion and neurotransmitter function, which increases vulnerability to postoperative delirium and cognitive decline. Cardiovascular changes include arterial stiffening from elastin fragmentation and collagen cross-linking, forcing the heart to compensate through left ventricular hypertrophy and increasing the risk of diastolic dysfunction and ischemia. The respiratory system becomes mechanically compromised as the chest wall stiffens and lung tissue loses elastic recoil, causing closing volume to approach tidal volume and predisposing elderly patients to atelectasis and progressive hypoxemia. Renal function declines through senile hypofiltration and tubular dysfunction, eliminating the capacity to maximally concentrate or dilute urine and leaving patients highly susceptible to dehydration and fluid overload. Body composition shifts unfavorably with loss of muscle mass and intracellular fluid while total body fat increases, reducing the central volume of distribution for water-soluble drugs while prolonging effects of lipid-soluble drugs. Frailty represents a critical state of reduced physiologic reserve that impairs the ability to withstand surgical stress and doubles or quadruples perioperative mortality risk. Geriatric syndromes including delirium, falls, incontinence, and dementia are phenotypic expressions of frailty and strong predictors of postoperative complications. Anesthetic management requires substantial dose reductions across all drug classes: minimum alveolar concentration for volatile anesthetics decreases approximately 6% per decade, induction agents require up to 50% dose reduction, and midazolam needs 75% reduction due to prolonged effects and delirium risk. Meperidine must be avoided entirely because its active metabolite normeperidine accumulates and strongly precipitates delirium. Perioperative care demands comprehensive preoperative assessment incorporating frailty evaluation, nutritional status, functional capacity using Activities of Daily Living, and cognitive screening with tools like the Mini-Cog. Intraoperative management emphasizes strict goal-directed fluid therapy since elderly patients tolerate neither hypovolemia nor hypervolemia well, careful positioning to prevent skin breakdown, and precise temperature control as shivering dramatically increases metabolic demand. Postoperative prevention of delirium relies on multicomponent nonpharmacologic interventions including sleep optimization, reorientation strategies, early mobilization, and restoration of sensory aids. Pain assessment requires specialized approaches for cognitively impaired patients, with particular vigilance against agonist-antagonist opioids due to their high delirium risk.