The Effect of Humidified, Warmed CO2 during Open Colorectal Surgery on Body Temperature and Postoperative Pain: A Randomized Controlled Trial

Background: Open abdominal surgery exposes the intestine to negative ventilation (20 °C; 0-5% RH), which given the large surface area of the peritoneum, can facilitate the loss of body heat. This study examined whether warmed, humidified CO2 (WHCO2) can reduce heat loss and decrease postoperative pain. Methods: A randomized controlled trial was performed at a tertiary colorectal unit (Concord Repatriation General Hospital, The University of Sydney, Australia). The study group received WHCO2 at a rate of 10L/ min. The control group did not receive any insufflation during the operation. Patients were over 18 years of age undergoing elective open colorectal operations. Core body temperature measurements were made every 15 minutes with a trans-esophageal probe. Postoperative pain was assessed via (1) the duration of use of patientcontrolled analgesia (PCA) and (2) the total oral morphine equivalent daily dose (oral MEDD). Results: In total, 39 patients were recruited in the study, with 20 receiving WHCO2. There was no difference in the core body temperature between the WHCO2 and control groups (36.1 vs. 35.9 °C; P=0.35). There was also no remarkable dissimilarity in the percentage of the operating time when the core body temperature dropped below the lower limit of normal, namely 35.8 °C (28.4 vs. 35.8 %; P=0.51), or fell below the level of hypothermia, i.e., 35°C (7.7 vs. 13.4 %; P=0.50). No differences in postoperative PCA duration and MEDD were noted between the WHCO2 and control groups. Conclusion: We conclude that WHCO2 neither affected the core body temperature during open colorectal surgery nor the postoperative pain experienced.