Hypothermia in the intensive care unit after surgery: a registry based retrospective cohort study.

Background: Hypothermia is common in patients admitted to the ICU after surgery; however, its relationship with postoperative outcomes has not been fully explored. This study investigates the association between postoperative hypothermia in the ICU and patient mortality. Methods: Retrospective cohort study using the Australian and New Zealand Intensive Care Society adult patient database. Postoperative noncardiac surgical ICU admissions between 2018 and 2023 were included. Hypothermia was defined as temperature <36°C. The lowest temperature recorded within the first 24 hours of ICU admission was used. The primary outcome was in hospital mortality with secondary outcomes including ICU mortality rate, length of stay and ICU readmission rates. Descriptive and multivariable logistic regression models were used to investigate the relationship between postoperative temperature and mortality. Results: Of 425,648 postoperative admissions to the ICU, 165,111 (38.8%) experienced hypothermia within 24 h of their admission. Patients with hypothermia had higher hospital mortality rates of 4.3%, compared with 2.1% in the normothermia group (adjusted odds ratio 1.34; 95% confidence interval 1.28-1.39). Mortality rates increased with lower temperatures with the 32-32.9°C group experiencing the highest mortality rate (adjusted odds ratio 3.03; 95% confidence interval 2.30-4.00). ICU readmission rates and hospital and ICU length of stay were similar between groups. Conclusions: In this retrospective cohort study we report that ostoperative hypothermia in the ICU setting is common in Austrailia and New Zealand and was associated with an increased mortality rate. Early recognition and prevention of hypothermia in the intensive care setting may be a modifiable risk factor to reduce mortality for this patient cohort.