Effect of Warmed Humidified CO2 on Peritoneum During Laparotomy

Forty patients undergoing open colorectal surgery will be recruited in this randomized controlled trial.

The study group will receive warmed (37°C), humidified (98% RH) carbon dioxide. The delivered gas will be defined by the United States Pharmacopeia and National Formulary, which requires impurity of less than 200 parts per million, including water vapour. This medical grade CO2 will be warmed to 37°C and humidified to 98% RH using humidification system. The sterility of the system will be assessed regularly as per protocol.

The control group will receive no gas insufflation into the open laparotomy wound. This is current standard practice for all patients undergoing open laparotomy for colorectal resection.

The device that will be used for insufflation of sterile, humidified, warmed CO2 is the Fisher & Paykel's HUMIGARD (Fisher & Paykel Healthcare Ltd, Auckland, New Zealand).

It consists of a bacterial filter and a humidification chamber filed with 180mL sterile water, positioned on a humidifier controller that includes an integrated temperature and flow sensor. The outlet of the humidification chamber is connected to a thermally insulated 2.5m-long heated insufflation tube that maintains temperature and humidity of the gas to its outlet. The warm and humidified CO2 enters a gas diffuser (ST300DF VITA-diffuserTM, Cardia Innovation AB, Stockholm, Sweden) consisting of a 25cm-long polyvinylchloride tube (inner diameter of 2.5mm) with polyurethane foam at its end. The cylindrical polyurethane foam tip diverts the gas jet in multiple directions via the many small paths inside the foam. The gas is thus uniformly distributed and the large diffuser surface area greatly reduces the velocity of the outflow. Thus the system delivers humidified CO2 at 100% relative humidity and 37C to the surgical wound. The gas diffuser will be positioned inside the open abdominal wound cavity (in the right cranial quadrant) at a depth of approximately 4cm from the skin as soon as the abdominal wall retraction has been done. The insufflation of warm humidified CO2 will then start and continue until the abdominal wall retractors are removed and abdominal wall is commenced to be closed.

Calculation of Power: The investigators estimated sample size of 40 patients for 80% power using the literatures' reported standard deviation of levels of 3-chlorotyrosine (which is one of the study's primary biochemical markers of inflammation)

ANALYSIS OF BIOCHEMICAL AND MOLECULAR MARKERS: Where acquired, samples of the human tissue obtained (above) will be homogenised and assigned to biochemistry and molecular analyses. Total RNA will be extracted using a commercial kit, converted to cloned DNA and then probed for various pro-inflammatory genes. Where a change in gene regulation is noted, the investigators will assess the corresponding change in protein level using a combined approach consisting of multiplex ELISA to quantify changes in protein levels and further confirmation with Western blotting using corresponding specific antibodies.

STATISTICAL ANALYSIS: Statistical analysis will be performed using SPSS for Windows version 18.0 GradPack (IBM, New York, USA). Non-parametric continuous variables will be tested using Mann-Whitney U tests and parametric continuous variable will be tested using t-test/ANOVA. Categorical variables will be tested using Fisher exact test.

OUTCOME AND STUDY END POINT:

The study will involve both clinical and laboratory based work, and the outcomes are as follows.

• Laboratory based work:

From each patient, 4 samples will be taken and hence 160 samples will be analysed.

From each sample, the investigators will analyse the activation of pro-inflammatory cells (polymorphs, macrophages), level of messenger RNA.

The investigators will analyse level of (pro)inflammatory cytokines-- IL1,2,6,9,10, and TNF.

The investigators will assess the relationship between time (duration of operation) and the inflammatory markers.

The study will aim to prove that prove that as duration of operation increase, the extent of in inflammation the intestine's surface increases, and that this process can be mitigated by using humidified warmed carbon dioxide gas.

• Clinical based work:

The study will see whether use of humidified, warmed carbon dioxide gas results in:

• Better core body temperature control
• Less postoperative pain
• Shorter hospital stay
• Less risk of complications, including wound infection, anastomotic leaks.

Inclusion criteria

• Adults above age 18.
• Elective patients.
• Pathologies: colorectal carcinoma, polyposis syndromes, diverticular diseases, prolapses, and patients with inflammatory bowel disease undergoing elective resection.
• For colorectal carcinoma, all patients whether they are having curative or palliative surgery will be included.
• Patients undergoing open elective colectomy, with or without stoma formation/ bowel anastomosis.

Exclusion criteria

• Patients undergoing acute surgery (emergency surgery).
• Patients undergoing Laparoscopic colectomy (multiport, single incision and also hand assisted) as all these patients receive heated humidified CO2.
• For COPD patients, the exclusion criteria would be patients: (1) On home oxygen, (2) Type 2 respiratory failure (CO2 retainers) (3) FEV1<1L, or FEV1/FVC <50% of predicted