Turning Down Ileus: Does Intraoperative Warm Humidified CO ₂ Improve Return of Bowel Function After Open Colorectal Surgery?

BackgroundPostoperative ileus (POI) remains one of the most common and costly complications following open colorectal surgery, prolonging hospital stay and delaying recovery despite the widespread adoption of Enhanced Recovery After Surgery (ERAS) protocols. Warm humidified carbon dioxide insufflation (WHCI), delivered intraoperatively at 37°C and near-100% humidity, has emerged as a promising adjunct to preserve peritoneal physiology in open surgery. By maintaining normothermia, reducing tissue desiccation, attenuating systemic inflammation, and supporting tissue oxygenation, WHCI may directly address several mechanisms implicated in the pathogenesis of POI.PurposeTo outline the physiological rationale for WHCI in open abdominal surgery and introduce a multicentre randomised controlled trial designed to determine whether WHCI accelerates return of bowel function following open colorectal surgery.Research DesignPerspective article incorporating a narrative review of existing evidence and the protocol overview of a forthcoming multicentre, single-blinded randomised controlled trial.Study SampleThe proposed trial will enrol 264 adults (132 per arm) undergoing elective or emergency open colorectal surgery across three Monash Health hospitals (Dandenong, Monash Medical Centre, and Casey), with randomisation stratified by urgency.Data Collection and AnalysisThe primary outcome will be the proportion of patients regaining bowel function (passage of flatus or stool) within 72 hours postoperatively, assessed at 24-hour intervals. Secondary outcomes include length of stay, readmission, return to theatre, postoperative nausea and vomiting, and use of oral Gastrografin follow-through. Sample size calculations anticipate a reduction in POI from 30-35% to 15%, with α = 0.05 and 80% power, allowing for 10% attrition.ResultsExisting evidence from open colorectal, cardiac, and orthopaedic surgery demonstrates reductions in peritoneal mesothelial injury, lower postoperative C-reactive protein, improved wound and core temperature, and reduced intra-wound particulate contamination. However, no adequately powered trial has yet evaluated whether these physiological benefits translate into faster return of bowel function.ConclusionsWHCI is a physiologically grounded, low-risk, and low-cost intraoperative adjunct that may directly address several mechanisms implicated in the pathogenesis of POI. If validated by the proposed trial, WHCI could redefine perioperative best practice and extend the thermoregulatory standards of laparoscopy into open surgery.