Intraoperative body temperature and emergence delirium in elderly patients after non-cardiac surgery: A secondary analysis of a prospective observational study

BACKGROUND: Emergence delirium (ED) is a kind of delirium that occured in the immediate post-anesthesia period. Lower body temperature on post-anesthesia care unit (PACU) admission was an independent risk factor of ED. The present study was designed to investigate the association between intraoperative body temperature and ED in elderly patients undergoing non-cardiac surgery. METHODS: This study was a secondary analysis of a prospective observational study. Taking baseline body temperature as a reference, intraoperative absolute and relative temperature changes were calculated. The relative change was defined as the amplitude between intraoperative lowest/highest temperature and baseline reference. ED was assessed with the confusion assessment method for intensive care unit at 10 and 30 min after PACU admission and before PACU discharge. RESULTS: A total of 874 patients were analyzed with a mean age of 71.8 ± 5.3 years. The incidence of ED was 38.4% (336/874). When taking 36.0°C, 35.5°C, and 35.0°C as thresholds, the incidences of absolute hypothermia were 76.7% (670/874), 38.4% (336/874), and 17.5% (153/874), respectively. In multivariable logistic regression analysis, absolute hypothermia (lowest value <35.5°C) and its cumulative duration were respectively associated with an increased risk of ED after adjusting for confounders including age, education, preoperative mild cognitive impairment, American Society of Anesthesiologists grade, duration of surgery, site of surgery, and pain intensity. Relative hypothermia (decrement >1.0°C from baseline) and its cumulative duration were also associated with an increased risk of ED, respectively. When taking the relative increment >0.5°C as a threshold, the incidence of relative hyperthermia was 21.7% (190/874) and it was associated with a decreased risk of ED after adjusting above confounders. CONCLUSIONS: In the present study, we found that intraoperative hypothermia, defined as either absolute or relative hypothermia, was associated with an increased risk of ED in elderly patients after non-cardiac surgery. Relative hyperthermia, but not absolute hyperthermia, was associated with a decreased risk of ED. REGISTRATION: Chinese Clinical Trial Registry (No. ChiCTR-OOC-17012734).