Abstract Background and objectives Postoperative delirium is common in critically ill patients and is known to have several predisposing and precipitating factors. Seasonality affects cognitive function which has a more dysfunctional pattern during winter. We, therefore, aimed to test whether seasonal variation is associated with the occurrence of delirium and hospital Length Of Stay (LOS) in critically ill non-cardiac surgical populations. Methods We conducted a retrospective analysis of adult patients recovering from non-cardiac surgery at the Cleveland Clinic between March 2013 and March 2018 who stayed in Surgical Intensive Care Unit (SICU) for at least 48 hours and had daily Confusion Assessment Method Intensive Care Unit (CAM-ICU) assessments for delirium. The incidence of delirium and LOS were summarized by season and compared using chi-square test and non-parametric tests, respectively. A logistic regression model was used to assess the association between delirium and LOS with seasons, adjusted for potential confounding variables. Results Among 2300 patients admitted to SICU after non-cardiac surgeries, 1267 (55%) had postoperative delirium. The incidence of delirium was 55% in spring, 54% in summer, 55% in fall and 57% in winter, which was not significantly different over the four seasons (p= 0.69). The median LOS was 12 days (IQR = [8, 19]) overall. There was a significant difference in LOS across the four seasons (p= 0.018). LOS during summer was 12% longer (95% CI: 1.04, 1.21; p= 0.002) than in winter. Conclusions In adult non-cardiac critically ill surgical patients, the incidence of postoperative delirium is not associated with season. Noticeably, LOS was longer in summer than in winter.

Abstract Background The effect of regional analgesia on perioperative infectious complications remains unknown. We therefore tested the hypothesis that a composite of serious infections after colorectal surgery is less common in patients with regional analgesia than in those given Intravenous Patient-Controlled Analgesia (IV-PCA) with opiates. Methods Patients undergoing elective colorectal surgery lasting one hour or more under general anesthesia at the Cleveland Clinic Main Campus between 2009 and 2015 were included in this retrospective analysis. Exposures were defined as regional postoperative analgesia with epidurals or Transversus Abdominis Plane blocks (TAP); or IV-PCA with opiates only. The outcome was defined as a composite of in-hospital serious infections, including intraabdominal abscess, pelvic abscess, deep or organ-space Surgical Site Infection (SSI), clostridium difficile, pneumonia, or sepsis. Logistic regression model adjusted for the imbalanced potential confounding factors among the subset of matched surgeries was used to report the odds ratios along with 95% confidence limits. The significance criterion was p < 0.05. Results A total of 7811 patients met inclusion and exclusion criteria of which we successfully matched 681 regional anesthesia patients to 2862 IV-PCA only patients based on propensity scores derived from potential confounding factors. There were 82 (12%) in-hospital postoperative serious infections in the regional analgesia group vs. 285 (10%) in IV-PCA patients. Regional analgesia was not significantly associated with serious infection (odds ratio: 1.14; 95% Confidence Interval 0.87‒1.49; p-value = 0.339) after adjusting for surgical duration and volume of intraoperative crystalloids. Conclusion Regional analgesia should not be selected as postoperative analgesic technique to reduce infections.