62: Geriatric Anesthesia

Published on 06/02/2015 by admin

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CHAPTER 62 Geriatric Anesthesia

Gurdev S. Rai, MD

1 What is geriatric anesthesia and why is it important?

image Geriatric anesthesia is defined as providing anesthetic care for patients older than 65 years old.
image The geriatric population of the United States exceeds 35 million people, 12% of the total population. This population accounts for 33% of all surgical procedures performed in the United States.
image Geriatric patients consume 50% of the U.S. Federal Health Care Budget.
image Their population is expected to double by the year 2050.

2 What are the overriding characteristics and principles governing age-related physiologic changes as they relate to anesthesia in geriatrics?

Basal function of most organ systems is relatively unchanged by the aging process per se, but the functional reserve and ability to compensate for physiologic stresses is reduced. However, because of the diversity of this population, it is difficult to predict the extent of age-related physiologic changes and reduction in functional reserve for any particular individual.

3 Review age-related changes to the cardiovascular system

image Age-related wall thickening and stiffening of large elastic arteries reduces their compliance and increases afterload on the heart. These vascular changes can occur in the absence of atherosclerosis or hypertension and are independent predictors of mortality.
image Increased afterload (e.g., from hypertension) produces ventricular hypertrophy, leading to increases in wall stress, myocardial oxygen demand, and risk of ischemia.
image Diastolic dysfunction secondary to ventricular remodeling minimizes the ability to adjust stroke volume in response to changes in intravascular volume and tone.
image Stroke volume becomes more dependent on atrial preload for adequate end-diastolic volume.
image The atrium dilates as a result of impaired outflow secondary to ventricular remodeling, making the elderly more prone to atrial fibrillation. Fatty infiltration and fibrosis of myocardium manifests in conduction abnormalities and decreased heart rate variability.
image Down-regulation of β-adrenergic receptors magnifies the decreased ability of the heart to reach maximal cardiac output acutely in response to stress.

4 Describe age-related changes to the pulmonary system

image Restrictive pulmonary changes are noted as increased thoracic stiffness increases the work of breathing and decreases maximal minute ventilation.
image Closing capacity surpasses functional residual capacity by age 65 years, increasing the risk of atelectasis.
image Decreased cough reflex, ciliary clearance, and compromised swallowing mechanics increase risk of perioperative aspiration and pneumonia.
image There is a centrally mediated decrease in ventilatory response to hypoxia and hypercapnia.
image Exposure time to environmental, genetic, and social factors increases the prevalence of lung diseases and further exaggerates the changes noted previously.

5 Discuss age-related changes to the nervous system

image There is overall cerebral atrophy, decreased complexity of neuronal connections and decreased synthesis of neurotransmitters, increased fibrosis of peripheral sympathetic neurons, and impairment of cardiovascular reflexes.
image Decreased skeletal muscle innervation (and atrophy) results in decreased strength and fine motor control.
image There is increased sensitivity to all anesthetic agents.

6 How is baseline renal function impaired in the elderly?

There is progressive decrease in glomerular filtration rate (GFR) because of a decrease in renal blood flow and renal mass and diminishing tubular dysfunction, impairing sodium homeostasis and the ability to respond to acid loads. Under normal circumstances these have no real clinical implications other than subclinical hyponatremia. However, in the face of surgical stress, the failure to adapt to acute volume changes can lead to hemodynamic instability. Therefore meticulous attention needs to be paid to intraoperative fluid and electrolyte management in the elderly population.

7 How does serum creatinine change with aging?

Despite progressive decreases in GFR, because of an overall decrease in muscle mass in the elderly, serum creatinine should remain normal or decrease.

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