Peri-operative circadian rhythms & sleep

The circadian timing system (CTS) generates diurnal rhythms of ~24 hours to adapt human physiology to the day-night cycle. In this capacity, it also regulates the sleep-wake rhythm. Good sleep and a well-synchronized CTS are fundamental in human health. As a result, the CTS and sleep also play a vital role in patients undergoing surgery during the peri-operative phase. Part I of this thesis examines how surgery and anaesthesia affect the CTS and sleep-wake rhythm in the peri-operative phase. We found that surgery/anaesthesia cause a phase advance of the CTS and sleep quality reduction. The effect was stronger in later chronotype (i.e. owls, or evening persons), and was found in adults, but not in children. Part II covers how the CTS of patients and the time-of-day of surgical procedures influences clinical outcomes. After-hours surgery was associated with a higher incidence of mortality and morbidity. Additionally, post-induction hypotension, a common intra-operative complication, was more frequent in morning surgery than in afternoon surgery. Lastly, in Part III, we tried to improve sleep and reduce CTS disturbance in both non-surgical and surgical hospitalised patients admitted in the hospital. The sleep quality of non-surgical patients improved after implementation of a multicomponent sleep-improving intervention, but the same bundle of interventions did not affect surgical patients’ sleep. As surgical patients are more at-risk for CTS- and sleep disturbance and better sleep would improve postoperative recovery, more work remains to be done.