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People over 65 years of age are 3.5 times more likely to have surgery. Aging results in a progressive decline in the functional reserve of all organs; the rate at which function diminishes is highly variable between individuals.
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- Cardiovascular
- Decreased arterial elasticity:
- Increased afterload
- Left ventricular hypertrophy
- Increased systolic blood pressure, mean arterial pressure, and pulse pressure
- Autonomic imbalance:
- Increased vagal tone
- Decreased sensitivity of adrenergic receptors
- Decreased baroreceptor reflex
- Fibrosis of the conducting system and loss of sinoatrial node cells
- Sclerosis/calcification of valves
- High incidence of diastolic dysfunction
- Respiratory
- Decreased lung tissue elasticity (due to reorganization of collagen and elastin):
- Early collapse of small airways and overdistension of alveoli (V/Q mismatch)
- Increased residual volume (total lung capacity unchanged)
- Increased closing capacity
- Decreased arterial oxygen tension
- Loss of alveolar surface area (increased anatomic and physiologic dead space)
- Increased V/Q mismatch
- Increased chest wall rigidity leading to increased work of breathing
- Blunted response to hypercapnia, hypoxia, and mechanical stress
- Decreased protective reflexes (coughing and swallowing) increasing the risk for aspiration
- Increased pulmonary vascular resistance and pulmonary arterial pressure
- Blunted hypoxic pulmonary vasoconstrictive response
- Renal
- Decreased renal mass:
- Mostly renal cortex secondary to decreased functioning glomeruli
- Progressive decline in creatinine clearance
- Increased risk of perioperative acute renal failure
- Decreased renal blood flow:
- Decreases 10% every decade of aging
- Serum creatinine unchanged due to loss of muscle mass
- Decreased tubular function:
- Altered sodium balance, urine concentrating ability, and drug excretion
- Increased risk for dehydration and electrolyte abnormalities
- Decreased renin–aldosterone system resulting in impaired potassium excretion
- Neurologic
- Decreased brain mass, particularly the cerebral cortex (frontal lobes)
- Cerebral blood flow decreases 10–20%, although autoregulation stays intact
- Decreased neurotransmitter synthesis: GABA, serotonin, dopamine, norepinephrine, and acetylcholine system
- Variable degrees of cognitive function decline, especially short-term memory
- Decreased general anesthesia (MAC) and local anesthetic requirements
- Gastrointestinal
- Decreased liver function secondary to reduced liver mass and hepatic blood flow:
- Reduced biotransformation
- Decreased albumin production
- Decreased plasma cholinesterase
- Delayed gastric emptying
- Increased gastric pH
- Musculoskeletal
- Reduced muscle mass; atrophic skin; frail veins
- Increased body fat; total body water decreases
- Arthritis can affect various joints that can complicate positioning
- Degenerative changes of the cervical spine; intubation potentially more difficult
- Endocrine/metabolic
- Atrophy of endocrine glands leading to impaired hormone function:
- Insulin, thyroxine, growth hormone, testosterone
- Blunted neuroendocrine stress response
- Decreased heat production and alteration in hypothalamic temperature-regulating center increases risk of hypothermia
- Age-related pharmacologic effects
- Increased body fat and decreased total body water:
- Higher plasma concentration of water-soluble drugs
- Lower plasma concentration of fat-soluble drugs
- Reduced clearance secondary to decreased hepatic and renal function
- Altered protein binding:
- Reduced albumin affects binding of acidic drugs (opioids, barbiturates, benzodiazepines)
- Increased α1-acid glycoprotein affects binding of basic drugs (local anesthetics)
- Pharmacodynamic changes:
- Drug effects may be intensified due to decreased number of available receptors
- Reduced anesthetic requirement (or MAC)
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- Perform a thorough history and physical examination and determine appropriate preoperative testing (based on clinical correlate)
- Assess optimization of preexisting conditions such as CAD, ...