Diurnal variations in recovery times after general anaesthesia in children

Background: Circadian rhythms coordinate almost all physiological functions and are implicated in major disease development. Even though circadian rhythms have a major impact on human health, little is known about how they affect general anaesthesia. The purpose of this study was to understand if the time of day affects the length of time a child needs to achieve readiness for discharge after general anaesthesia for brain MRI. Methods: A retrospective analysis over a 3 yr period (2013-5) on the length of stay in the postanaesthesia care unit (PACU) before discharge was performed for children (age <18 yr) undergoing brain magnetic resonance imaging as outpatients. PACU duration was correlated to either morning vs afternoon or to time clusters for discharge times (<9 AM, >9 AM <12 PM, >12 PM <3 PM, >3 PM <6 PM, >6 PM). Results: Data from 2340 procedures in children, with median age [inter-quartile range (range)] of 4.7 [2.3-7.25 (0.5-17.8)] yr were available for analysis. The length of stay in the PACU significantly increased over the course of the day with an observed maximum increase of 18 or 19 min (<9 AM vs >6 PM) in children older than 3 or 5 yr, respectively. Subgroup analysis suggested time of day dependent PACU time increase was independent of sex, co-medications, or obstructive sleep apnoea. Conclusion: The time of day significantly affects PACU recovery times in children of both genders having brain imaging under general anaesthesia. Children younger than 3 yr might not be affected. Further validation of these findings may guide future strategies to reduce discharge times.