The relationship between surgical wound environment and physiology in laparotomy patients.

In Dunedin Hospital some general surgical teams use the F&P HumiGard™ Surgical Humidification device (Fisher and Paykel Healthcare Ltd, Auckland, NZ) as an additional method to maintain patient temperature and tissue hydration during surgery, and some surgical teams do not. Based on the inclusion criteria and patient consent we will observe and collect measurement data from 15 cases that do not use surgical humidification (control group) and 15 cases that do use surgical humidification. Participants are not randomised and receive standard care according to the surgeon’s clinical practice. HumiGard™ is to be used intraoperatively during surgery according to the surgeons standard clinical practice. The HumiGard system is comprised of a patient interface (SI400), tubing kit (ST340), humidifier (SH875), and flow control (900SH701). HumiGard™ delivers warm and moist carbon dioxide gas to the patient’s surgical site intraoperatively and is designed to keep patients warm and their surgical site moist during surgery. Data Collection Preoperative Observations Relevant demographic and clinical characteristics will be retrieved from patients' electronic medical records, including: • Date of birth, gender, ethnicity, weight, height, body mass index (BMI) • American Society of Anaesthesiology (ASA) scores and National Early Warning Score 2 (NEWS2) • Smoking, vaping, or nicotine patch usage • Medical history (e.g., diabetes, hypertension, prior abdominal surgeries, comorbidities, concomitant medications, current diagnosis, and reason for surgery) Intraoperative Observations Key surgical and patient variables will be recorded, such as: • Time of induction and operating theatre temperature at induction • Patient warming methods (if applicable) • Surgical incision length and location, time of skin incision, and retractor placement • Timing of HumiGard™ activation and deactivation (if applicable) • Core body temperature monitoring (if routinely recorded), including probe type and hourly temperature measurements from induction to the end of surgery • Systemic blood gas analysis (if conducted), noting blood draw site and final pH, pO2, and pCO2 values prior to closure • Irrigation fluid type, timing, approximate volume, and temperature used intraoperatively • Estimated blood loss, transfusion requirements (units) Postoperative Observations Standard postoperative monitoring will include: • Daily C-reactive protein (CRP) blood tests from postoperative day 1 to day 5 • Patient arrival and discharge times from the Post-Anaesthesia Care Unit (PACU) • Core body temperature (if routinely measured) upon PACU arrival and discharge • Hospital length of stay, including admission, surgery, and discharge dates/times • Documentation of known incisional surgical site infections (SSI) or ileus until discharge • Recording of adverse events (AEs), serious adverse events (SAEs), adverse device effects (ADEs), and serious adverse device effects (SADEs) from incision to discharge. Wound-related complications (e.g., seroma, hematoma, wound dehiscence, hernia, SSI) tracked up to 30 days post-operation Additional Research Procedures As part of the research component ooutside of standard hospital practice, participants will undergo: • A one-time preoperative CRP blood test before surgical incision • Non-invasive Intraoperative imaging of the surgical site at the start and end of surgery to assess tissue appearance, temperature, and oxygenation. • A patient-reported wound healing questionnaire (Bluebelle Wound Healing Questionnaire) completed 30 days post-operation