Use of Brain Wave Monitoring During Surgery to Reduce Postoperative Cognitive Dysfunction

This research study is being done to determine if indices derived from monitoring brain wave activity while under general anesthesia will predict the likelihood of post-operative cognitive dysfunction in patients over 60 years old.

Postoperative cognitive dysfunction (POCD) occurs in 30-40% of older adults after undergoing surgical procedures. POCD be subtle, such as a formerly avid reader unable to read for comprehension, to more overt, such as the inability to perform self-care. This deterioration in cognitive function leads to increased mortality, premature departure from the labor market and economic hardship. With 25 million people over the age of 60 undergoing surgical procedures annually in the United States and most of them living long into their 8th decade, prevention of POCD is an important public health issue. The causal mechanism of POCD remains unclear, though older patients who receive general anesthesia are at increased risk relative to younger patients. While the association between age and POCD is not fully understood, several normal, age-related changes to brain anatomy and physiology may explain the increased susceptibility. These include decreased brain volume, notably in the prefrontal cortex, cortical thinning and altered neurotransmitter function. Taken together, these changes decrease the anesthetic requirements for older patients to achieve a similar anesthetic state and make them susceptible to overdosing of anesthetic agents. This is supported by studies using electroencephalography (EEG) to measure cerebral cortical activity which have demonstrated profound age-related differences for patients receiving general anesthesia. Older patients are more likely to develop burst suppression, an EEG pattern associated with an excessive anesthetic state. Currently, a major limitation in the field is the absence of studies that have used raw EEG data to examine the association between the dosing of anesthetic agents and POCD in older patients. Although prior studies have used EEG-derived depth of anesthesia indices to explore this association, these indices have been shown to be an unreliable measure of anesthetic state in older patients. Thus, the question of whether an excessive anesthetic state in this population causes POCD remains unanswered. The investigators will recruit 100 adults over 60 years of age who undergo elective surgery under general anesthesia with EEG monitoring. A brief neurocognitive test battery will be conducted before surgery, 3-7 day post-surgery, and 3 months post-surgery to assess the association between EEG suppression and POCD. In this study, the investigators hypothesize that the duration of EEG suppression is associated with POCD.