ORIGINAL ARTICLES Warming and Humidification of Insufflation Carbon Dioxide in Laparoscopic Colonic Surgery A Double-Blinded Randomized Controlled Trial Tarik Sammour, MBChB,* Arman Kahokehr, MBChB,* Julian Hayes, FRACS,† Mike Hulme-Moir, FRACS,‡ and Andrew G. Hill, MD (Thesis), FRACS* Objective: We aimed to test the hypothesis that warming and humidifi- cation of insufflation CO 2 would lead to reduced postoperative pain and improved recovery by reducing peritoneal inflammation in laparoscopic colonic surgery. Summary Background Data: Warming and humidification of insufflation gas is thought be beneficial in laparoscopic surgery, but evidence in pro- longed laparoscopic procedures is lacking. Methods: We used a multicenter, double-blinded, randomized controlled design. The Study Group received warmed (37°C), humidified (98% RH) insufflation carbon dioxide, and the Control Group received standard gas (19°C, 0% RH). Anesthesia and analgesia were standardized. Intraoperative oesophageal temperature was measured at 15 minutes intervals. At the conclusion of surgery, the primary surgeon was asked to rate camera fogging on a Likert scale. Postoperative opiate usage was determined using Morphine Equivalent Daily Dose (MEDD), and pain was measured using visual analogue scores. Peritoneal and plasma cytokine concentrations were mea- sured at 20 hours postoperatively. Postoperative recovery was measured using defined discharge and complication criteria, and the Surgical Recovery Score. Results: Eighty-two patients were randomized, with 41 in each arm. Groups were well matched at baseline. Intraoperative core temperature was similar in both groups. Median camera fogging score was significantly worse in the Study group (4 vs. 2, P = 0.040). There were marginal differences in pain scores, but no significant differences were detected in MEDD usage, cyto- kine concentrations, or any recovery parameters measured. Conclusion: Warming and humidification of insufflation CO 2 does not attenuate the early inflammatory cytokine response, and confers no clinically significant benefit in laparoscopic colonic surgery. (Ann Surg 2010;251: 1024 –1033) I n laparoscopic surgery, the abdominal wall is distended using pneumoperitoneum to provide room for instrument insertion and tissue dissection. Carbon dioxide (CO 2 ) is used almost universally as the insufflation gas of choice. 1 This is commonly delivered as defined by the United States Pharmacopeia and National Formulary, which requires impurity of less than 200 parts per million, including water vapor. 2 Medical grade CO 2 is supplied as a compressed liquid in cylinders with a release temperature of approximately -90°C. 3 In the absence of active conditioning, the gas is passed through the insufflator and tubing apparatus raising its temperature to that of the room (19°C–21°C) with a relative humidity approaching 0% at the point of entry into the peritoneal cavity. 4 Despite several advances in technique, little has changed with this aspect of laparoscopic practice since it was established by Kurt Semm in the 1960s. 5 The effect of this continuous flow of cool, dry carbon dioxide on the peritoneal microenvironment has probably been under-estimated, 6–9 and there is evidence that it causes structural, morphologic, and biochemical injury to the peritoneal mesothelium. 3,10 –14 How much of this effect relates to intrinsic properties of CO 2 , and how much is due to the desiccative effect of the gas is debated 15,16 ; but there is some evidence that conditioning of insufflation gas by warming and humidification may be beneficial in this regard. 12,17–19 The clinical benefits have also been investigated. Proponents have argued that warming and humidification may reduce the incidence of intraoperative hypothermia, reduce postoperative pain and analgesia use, and improve postoperative recovery. 20 –26 How- ever, results have been conflicting. 27,28 Two meta-analyses have recently been published, and while they were able to demonstrate some significant benefits, conclusions were limited by the inclusion of mainly unblinded (or inadequately blinded) studies, and hetero- geneity in surgical indication. 29 –31 In addition, most trials did not control for the use of an external patient warming device (such as a warming blanket), and were conducted for laparoscopic procedures of relatively short duration. 29 There have not been any randomized controlled trials evaluating the use of warming and humidifica- tion in a prolonged laparoscopic surgical procedures such as colonic surgery, where it might be expected the effects would be most pronounced. We aimed to design and execute a prospective, double- blinded, randomized controlled trial to test the hypothesis that warming and humidification of insufflation gas during laparoscopic colonic surgery would lead to reduced postoperative pain and improved recovery by reducing peritoneal inflammation. METHODS Participants The study population included all New Zealand citizens and permanent residents residing within the catchment area of the 3 District Health Boards serving Auckland city (Auckland District Health Board DHB, Waitemata DHB, and Counties Manukau DHB). All patients undergoing elective laparoscopic colonic resec- tion for any indication and at any of the 3 public hospitals between April 2008 and June 2009 were screened for inclusion. Exclusion From the *Department of Surgery, South Auckland Clinical School, University of Auckland, Auckland, New Zealand; †Department of Surgery, Auckland City Hospital, Auckland, New Zealand; and ‡Department of Surgery, North Shore Hospital, North Shore City, New Zealand. Supported by the Surgeon Scientist Scholarship administered by the Royal Australasian College of Surgeons (to T.S.); The Ruth Spencer Fellowship administered by the Auckland Medical Research Foundation (to A.K.). Humidifiers and blinding covers were provided on loan to the hospitals from Fisher and Paykel Healthcare Limited, Auckland, New Zealand. Fisher and Paykel Healthcare limited were not in any way involved in study design, data collection, data analysis, or results write-up. Reprints: Dr Tarik Sammour, MBChB, Department of Surgery, South Auckland Clinical School, Private Bag 93311, Middlemore Hospital, Otahuhu, Auck- land, New Zealand. E-mail: tsammour@middlemore.co.nz. Copyright © 2010 by Lippincott Williams & Wilkins ISSN: 0003-4932/10/25106-1024 DOI: 10.1097/SLA.0b013e3181d77a25 balt6/z7c-aos/z7c-aos/z7c00610/z7c5016-10a wasifk S4 5/4/10 19:59 Art: SLA201842 Annals of Surgery • Volume 251, Number 6, June 2010 1024 | www.annalsofsurgery.com AQ: 1 AQ:4 Double-blinded RCT investigating warmed (37°C), humidified (98% RH) CO 2 versus standard insufflation gas in laparoscopic colonic surgery. Eighty-two patients were randomized. Median camera fogging score was worse in the study group. There were marginal differences in pain scores, but no differences in intraoperative temperature, opiate usage, cytokine concentrations, or recovery parameters.