Peri-Anesthetic Imaging of Cognitive Dysfunction

Overview

Recent data suggests that anesthetics can have prolonged effects on gene expression, protein synthesis and processing as well as cellular function in ways that the investigators are only beginning to understand, especially in the very young and the elderly. Within moments to days of emerging from anesthesia - cardiac or non-cardiac - some patients experience mild to very severe disorientation and changes in memory and thinking ability without apparent cause. For the vast majority of patients, this Post-Operative Cognitive Dysfunction (POCD), generally subsides, but for some with "diminished cognitive reserve" - especially the elderly, those with less education or prior CNS events such as stroke or early dementia - changes in memory and executive function may persist. If prolonged for more than three months, POCD has been linked to an increased risk of death. In 1-2% of elderly patients, the problem may ultimately continue for more than a year, leading to a loss of ability to care for themselves and early demise. Though this may seem like a small percentage, seniors will comprise up to 40% of the 50-75 million surgical procedures performed annually over the next 20-30 years. This amounts to 70,000 - 200,000 elder affected, and for them and their families, the cost of POCD in longer-term care, lost wages, and extended suffering will remain very high.

For more than 160 years, "modern" anesthesia has provided immense benefit to patients of all ages. However, over the past several years, concern has been growing that for patients at the extremes of age, some anesthetic agents may harbor subtle, previously minimally examined, serious neurotoxic effects which can cause lasting decline in the function of the central nervous system (CNS). For the elderly, these effects may manifest in lasting post-operative deterioration of memory and the capacity for normal information processing that can result in the inability to perform the activities of daily living (ADLs) with eventual early demise. Unfortunately, even though our ability to evaluate anesthetic risk has grown asymptotically for virtually every organ system, the brain remains neglected. And even though we know a good deal about effect sites for general anesthetic agents, we still have an incomplete understanding of the potential toxic effects of anesthetics on the brain. Therefore, employing a human surgical model (endoscopic prostatectomy), we propose a pilot study of 15 otherwise neurologically intact, ASA I - III, males, 65+ year of age. After pre-enrollment screening (MMSE \& BDI) and standard pre-op evaluation, subjects will undergo both anatomic and functional MRI studies plus a battery of neurocognitive tests (NCT) at two time points approximately 2-3 weeks apart prior to surgery. These pre-op studies will establish both a "non-surgical control" for the study as well as a baseline for post-op studies. 2-3 weeks after surgery, MRI and NCT will be repeated. The study aims to determine if MRI can demonstrate changes in the CNS pre-op vs post-op that relate to anesthesia and surgery and how those changes might correlate with NCT over the same interval.