Effect of Sedation on Cognitive Performance in the Elderly

Overview

The main goal of this study is to allow the anesthesiologist to make a more informed decision about the anesthetic requirement of a person prior to starting anesthesia. The preliminary data collected in this study will support a larger investigation aimed at gaining a better understanding of anesthetic susceptibility in general and in the elderly population which appears to be at greater risk for Postoperative Cognitive Dysfunction (POCD) POCD is a short-term decline in cognitive function (especially in memory and executive functions) that may last from a few days to a few weeks after surgery. In rare cases, this disorder may persist for several months after major surgery. POCD is distinct from emergence delirium. It occurs most commonly in older patients and those with pre-existing cognitive impairment. POCD is common in adult patients of all ages at hospital discharge after major non-cardiac surgery, but only the elderly (aged 60 years or older) are at significant risk for long-term cognitive problems. The body's inflammatory response to surgery likely plays an important role, at least in elderly patients. Investigators also postulate that a relative 'anesthetic overdose' may be a significant risk factor. Hence, being able to make a better judgment on the dose needed for an individual is extremely important.

Central nervous system (CNS) function is affected by sedation and anesthesia. This is evident from the desired clinical effects of sedative and anesthetic drugs. Recent evidence suggests that disruption CNS function may be prolonged and result in unwanted cognitive effects in predisposed individuals. Investigators know that there is a considerable pharmacokinetic (onset, distribution and elimination) and pharmacokinetic variability of neurotropic drugs even with in persons within a certain age and weight group. What the investigators do not know, is how to predict or quantify an individual's susceptibility to sedation and anesthesia and, more importantly, the potential cognitive susceptibility of an individual's brain to these drugs. Auditory functional imaging is a well validated task. It can be applied as a short (5 minute) test. Investigators know (preliminary data) that the size of the brain activation area changes after sedation. Investigators now postulate that this change reflects a disruption of neuronal integration in the brain and that this change may be an objective measure of the cognitive effects of sedation for an individual. As supportive data for an R-01 grant application the investigators propose to enroll 20 elderly subjects by public advertisement and quantify the effects of sedation with midazolam on auditory activation (auditory fMRI) and cognitive performance (mini Mental State exam and complex reaction time).