Perioperative brain functioning: Effects of anesthesia on neurometabolism, cognition and sleep-wake timing

This dissertation focuses on perioperative brain functioning. PART I examines cerebral glucose metabolism. We show that patients with preoperatively elevated glucose concentrations in the cerebrospinal fluid also have elevated cerebrospinal fluid polyol concentrations. We also observe that people with diabetes mellitus have higher levels of polyols in the cerebrospinal fluid compared to people without diabetes mellitus. We also show that polyols increase during surgery and remain elevated for at least two days despite only modest and short-term perioperative increases in plasma glucose.
PART II focuses on the effects that anesthesia and surgery exert on postoperative brain functioning. We show that patients with diabetes mellitus are at increased risk for short-term postoperative neurocognitive disorders (pNCD). We systematically review the existing literature on the role of intraoperative hypotension in the development of pNCD and find no conclusive association. Furthermore, we study the effects of surgery and anesthesia on diurnal sleep-wake patterns. We observe a perioperative diurnal phase shift associated with decreased subjective sleep quality, supporting the notion that sleep and sleep-wake rhythms can be negatively affected by surgery and anesthesia.
Part III focuses on tools for identifying pNCD. We examined the predictive value of intra-individual reaction time variability for postoperative delirium, but found that it is not an independent predictor for the development of postoperative delirium. Finally, we contrast cognitive screening tools for diagnosing pNCD with the gold standard (neuropsychological testing). We show that the two tests used are not reliable in diagnosing pNCD and should not be used for this purpose.