The Association Between Minor Brain Injuries and Level of Anesthesia Detected by a New EEG Based Tool, to Delirium and Post-operative Cognitive Dysfunction After Cardiac and Non-cardiac Surgery - a Proof of Concept Study

Detailed Summary

As the population ages and medical progress is made, many elderly patients that previously would not have been candidates for surgery are now undergoing operations. In this group of older patients, brain dysfunction after anesthesia and surgery is well recognized and categorized into two distinct clinical entities; Post-operative cognitive delirium (POD) and post-operative cognitive dysfunction (POCD). Delirium is an acute and fluctuating deterioration in attention accompanied by either a change in cognition or arousal and is often diagnosed by criteria established in the Confusion Assessment Method (CAM). Delirium can present as hypoactive (decreased alertness, motor activity and anhedonia), as hyperactive (agitated and combative) or as mixed forms. Age and the type of operation are the major risk factors. Post-operative cognitive dysfunction (POCD) is a term used to describe subtle changes in cognition, such as memory and executive function. The most commonly seen problems are memory impairment and impaired performance on intellectual tasks. In severe cases, it can lead to inability to perform daily living functions. It was previously found that the presence of cognitive dysfunction 3 months after non-cardiac surgery was associated with an increased mortality. The mechanisms leading to cognitive impairment after anesthesia and surgery are not yet fully clear. The risk factors are related to patient characteristics, type of operation and anesthetic management. Despite its limitations over-anesthesia as monitored by BIS was at-least correlative with POD. Therefore it is hopeful that an even more precise evaluation of the level of anesthesia will improve POD prediction (and thereby prevention) even further. On the other hand the measure of depth of anesthesia by itself does not provide sufficient prediction for POCD. In POCD a major role has been assigned to hippocampal damage. The investigators have recently demonstrated that temporary hippocampal interruptions are manifested by interhemispheric desynchronization, which are recognized by our new algorithm, which monitors electrophysiological markers of attention and of perception. The investigators have developed a unique algorithm for analyzing EEG based on the concept of monitoring perception and attention and their interhemispheric synchronization. The aims of this proof of concept study are: (i) to find-out whether interhemispheric desynchronization of attentional processes is associated with POCD; (ii) to find out whether the level of anesthesia, is linked primary to POD and secondary to POCD.

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