Anesthesia for Alzheimer Disease

ALZHEIMER DISEASE

Preoperative Considerations

Neurodegenerative diseases often lead to demen-tia. Along with a loss of gray matter, elderly patients have altered pharmacokinetic and phar-macodynamic responses to many drugs that are used to induce and maintain anesthesia or seda-tion. Alzheimer disease (AD) is the most common neurodegenerative disease, causing approximately 40% to 80% of all cases of dementia, with a preva-lence of approximately 20% in patients older than age 80 years. The disease is characterized by a slow decline in intellectual function. Progressive impairment of memory, judgment, and decision-making and emotional lability are hallmarks of the disease. Late in the course of the disease, severe extrapyramidal signs, apraxias, and aphasia are often present. Although some degree of brain atro-phy is normal with advancing age, patients with AD usually show marked cortical atrophy with ventricular enlargement; the pathological hall-marks of AD seen at necropsy include neurofi-brillary tangles that contain the phosphorylated microtubular protein tau and neuritic plaques composed of the peptide β-amyloid.

Anesthetic Considerations

Anesthetic management of patients with moder-ate to severe AD is often complicated by disori-entation and uncooperativeness. New onset oftemporary cognitive impairment is frequent in elderly patients and often persists for 1–3 days following surgery. Such patients require repeated reassurance and explanation. Legally incompe-tent patients cannot provide informed consent for anesthesia or surgery. Premedication is usually not given, and only small doses are used. Centrally acting anticholinergics, such as atropine and sco-polamine, may contribute to postoperative con-fusion. Glycopyrrolate, which does not cross the blood–brain barrier, may be the preferred agent when an anticholinergic is required.

Laboratory studies have shown that anesthetic agents are increasingly associated with neuronal injury and cell death The outcome implications of general anesthesia in both the elderly and small children are currently the subject of much inves-tigation and debate. Apoptotic neurodegenera-tion has been linked to the use of GABA receptor modulators and N-methyl-d-aspartic acid recep-tor antagonists, of which both mechanisms are used by common general anesthetics. Moreover, increased β-amyloid production is associated with both anesthetic exposure and AD. Consequently, there are concerns that anesthetic exposure may worsen dementia in the patient with AD; however, definitive conclusions regarding the risk of anes-thetic toxicity in the patient with AD are not yet available.