Association between intraoperative body temperature and postoperative delirium: A retrospective observational study

Study objective: The effect of perioperative body temperature derangement on postoperative delirium remains unclear. This study aimed to evaluate the association between intraoperative body temperature and post-operative delirium in patients having noncardiac surgery. Design: Single-center retrospective observational study. Setting: Tertiary university hospital. Patient: Adult patients who had major noncardiac surgery under general anesthesia for at least two hours be-tween 2019 and 2021. Interventions: Patients were classified into three groups according to their intraoperative time-weighted average body temperature: severe hypothermia (<35.0 degrees C), mild hypothermia (35.0 degrees C-36.0 degrees C), and normothermia (>= 36.0 degrees C) groups. Measurements: The primary outcome was the risk of delirium occurring within seven days after surgery, which was compared using logistic regression analysis. A multivariable procedure was performed adjusting for potential confounders including demographics, history of hypertension, diabetes, atrial fibrillation or flutter, myocardial infarction, congestive heart failure, and stroke or transient ischemic attack, preoperative use of antidepressants and statins, preoperative sodium imbalance, high-risk surgery, emergency surgery, duration of surgery, and red blood cell transfusion. Cox regression analysis was also performed using the same covariates. Main results: Among 27,674 patients analyzed, 5.5% experienced postoperative delirium. The incidence rates of delirium were 6.2% (63/388) in the severe hypothermia group, 6.4% (756/11779) in the mild hypothermia group, and 4.6% (712/15507) in the normothermia group. Compared with the normothermia group, the risk of delirium was significantly higher in the severe hypothermia (adjusted odds ratio, 1.43; 95% confidence interval, 1.04-1.97) and mild hypothermia (1.15; 1.02-1.28) groups. The mild hypothermia group also had a significantly increased risk of cumulative development of delirium than the normothermia group (adjusted hazard ratio 1.14; 95% confidence interval, 1.03-1.26). Conclusions: Intraoperative hypothermia (even mild hypothermia) was significantly associated with an increased risk of postoperative delirium.