Low Neurophysiologic Resistance to Anesthetics as a Marker of Preclinical/Prodromal Alzheimer's Disease and Neurovascular Pathology, Delirium risk and Inattention

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Project Summary/Abstract Delirium is a syndrome of fluctuating changes in alertness and attention that occurs in up to 40% of older surgical patients (i.e. age >65. Delirium is associated with an increased risk of developing dementia, a progressive loss of thinking and memory skills that eventually results in an inability to care for oneself and to live independently. The most common cause of dementia in older Americans is Alzheimer’s disease (AD) which is associated with a progressive buildup of abnormal deposits in the brain of two proteins, tau and amyloid beta. Amyloid beta deposits typically develop in the brain for years if not decades before the start of memory deficits and other AD symptoms. Patients with these early or “pre-clinical” amyloid beta deposits, even if they appear mentally normal, are often at increased risk of developing delirium after surgery. Here, we will examine whether these amyloid beta deposits, or other “pre-clinical” changes in brain structure and activity, predispose patients to show larger than normal brain activity changes in response to anesthetic drugs given during surgery. The central idea of this proposal is that an altered (or exaggerated) brain activity responses to anesthetic drugs is a marker of an unhealthy brain, i.e. a brain with signs of “pre-clinical” AD and which is at increased risk of postoperative delirium. First we will examine whether patients with evidence of brain amyloid beta pathology (as measured by spinal fluid amyloid beta levels) have altered brain activity responses to anesthetic drugs. Second, we will use brain imaging to determine whether changes early AD-like changes in brain structure and connections are associated with altered brain activity responses to anesthetic drugs. Third, we will determine whether altered brain activity responses to anesthetic drugs are associated with increased postoperative delirium occurrence and severity. This work will help us understand mechanisms underlying postoperative delirium and AD and related dementias, and the links between them. Further, this work will provide a way for anesthesiologists (and surgeons) to use brain activity recording data already in wide use in American operating rooms to predict which patients are likely to develop postoperative delirium and/or AD, which could allow these patients to be selected for interventions to prevent these disorders.