Effect of warm humidified insufflated carbon dioxide on wound bacterial load in open elective gastrointestinal surgery: a pilot investigation.

INTERVENTION: Patients will be randomly allocated to receive CO2 insufflation during their surgical procedure or standard care (Surgery without any additional intervention). The CO2 will be delivered into the open peritoneal cavity by the Fisher and Pykel HumigardTM surgical humidification system throughout the duration of the surgery (from incision to surgical close). The HumigardTM surgical humidification system creates a local atmosphere of CO2 heated to 37oC at 100% relative humidity which is thought to decrease airborne contamination, reduce bacterial growth and decreased heat loss during surgery. Intervention arm ‐ Consented patients undergoing Whipples procedure at Auckland City Hospital will receive insufflated CO2 in the surgical wound throughout the procedure. The Humigard TM device will be set up and operated by the consultant surgeon and the surgical team in the operating theatre. Swabs will be taken at time of incision, 1 hour, 2 hours and at surgical wound close. These swabs will be analysed for bacterial growth and compared against the patients how did not receive CO2. At time of incision and closure, 2 6mm skin biopsies will be taken along the incision line. This is to determine wound edge tissue response. A research nurse will be present throughout the procedure and will assist in sample collection and Humigard maintenance. All patients will be followed by a research nurse at 30 days over the phone to assess if there has been any surgical site infection. CONDITION: gastrointestinal surgery PRIMARY OUTCOME: To quantify the number of bacteria present in the open surgical wound as determined by taking swabs for qPCR. SECONDARY OUTCOME: Bacterial load as determined by taking swabs during surgery for culture of wound specimens (colony forming units). Wound edge tissue response as determined by analysis of 6mm tissue biopsies. These are taken at time of main abdominal incision and after 2 hours of surgery. Each biopsy will be either immediately fixed or frozen for tissue analysis. Analysis may include: gene expression arrays, immunohistochemistry, histology, protein profiles, metabolite and lipid profiles, cytokine and other appropriate laboratory investigations to measure the response of the skin edge to different gaseous environments. INCLUSION CRITERIA: 1. Scheduled to undergo upper gastrointestinal surgical procedures longer than 120 minutes involving an open midline laparotomy incision. 2. Able to give informed consent 3. Male or female between 18 and 65 years of age 4. HbA1c less than 49 mmol/mol