RADOX' Reduced Abdominal Distension and Oxygen Delivery

Design pilot study, single arm controlled study Hypothesis Deep neuromuscular blockade provided intraoperatively for patients undergoing laparoscopic colorectal surgery will have an increase in oxygen delivery as measured by haemodynamic data using oesophageal doppler. Secondary hypotheses Deep muscular blockade will provide the same surgical operating conditions at lower abdominal inflation pressures. The patients will experience less pain postoperatively due to less forced distension of the peritoneum demonstrated by less analgesic requirements. Patients will therefore spend less time in recovery and be able to mobilise earlier.Participants and Recruitment Patients will be assessed in preassessment clinic by a clinical nurse specialist for eligibility and provided with a patient information sheet. On the morning of planned surgery patients eligible who wish to be included in the study will be consented for the study in accordance with the International GCP guidelines by the anaesthetic researcher, and given a form to sign.

Sample size We estimate that 30- 40 participants will be required to demonstrate and statistical significance. Our unit carries out approximately 4 laparoscopic colorectal resections per week. Assuming that 30% of patients may not consent to participation or will not meet inclusion criteria we predict it will take less than 6- 12 months to enrol the necessary number of participants.

Preoperatively Participants will already be on the standardised Enhanced Recovery Programme. Intraoperatively An oesophageal Doppler probe will be inserted orally or nasally (standard practice in our unit for haemodynamic monitoring) to titrate fluids using stroke volume optimisation protocol (as per normal practice). Cardiovascular variables (heart rate, stroke volume, blood pressure and corrected flow time) will be collected prior to commencing surgery to provide baseline data set and throughout the procedure in accordance with routine observations under anaesthesia, which will together calculate oxygen delivery. Abdominal pressure will be measured continuously during insufflation and maintenance of the pneumoperitoneum (as per standard practice). Abdominal insufflation pressure will be gradually reduced as low as possible but ensuring the same standard of surgical access and operating conditions. Following completion of surgery the neuromuscular blockade will be reversed using a standardised dose of sugammadex 4mg/ kg according to the manufacturers guidelines according to neuromuscular monitoring returns a double burst stimulus to normal.

Postoperatively Immediately in the recovery area analgesia will be provided in accordance with enhanced recovery guidelines. Morphine Sulphate will be titrated to effect and a patient controlled analgesia pump given to the patient, which records quantity and demands of morphine used. .The standard enhanced recovery pathway will then be continued until discharge home.

Outcome measures Data collection for the primary endpoint will be collected from the haemodynamic data captured in theatre using the anaesthetic chart recording and oesophageal doppler. Data for the secondary endpoints will be pain scores in recovery and at 4 hours post operatively. Other secondary endpoints will be collected as standard by the Enhanced Recovery Nurse. These will include: length of operation, time spent in recovery area after surgery, time taken until mobilisation.