Transversus Abdominis Plane (TAP) Block for Postoperative Analgesia After Laparoscopic Colonic Resection

Overview

Laparoscopic (key-hole) large bowel resection is a minimally invasive procedure when compared to open large bowel resection, but is still associated with a significant amount of pain and discomfort. Analgesia is commonly provided by a multi-modal technique involving varying combinations of paracetamol, Non steroidal anti-inflammatory drugs (NSAIDs), regional analgesia and oral or parenteral opioids. While epidural analgesia is considered the gold standard for open colo-rectal procedures it can be associated with significant complications and may delay hospital discharge in laparoscopic procedures. Opioids are associated with an increased incidence of nausea, vomiting and sedation and reduced bowel motility which can also prolong recovery. Transversus Abdominis Plane (TAP) block is a technique which numbs the nerves carrying pain sensation from the abdominal wall and provides effective and safe analgesia with minimal systemic side effects. Their perceived benefits are thought to relate to reduced opioid consumption and therefore reduced opioid side effects. The investigators believe ultrasound guided TAP blocks will reduce pain and morphine consumption with a resultant improved patient satisfaction, earlier return of bowel function and earlier hospital discharge. The key research question the investigators are trying to answer is whether TAP block provide better pain relief than local anaesthetic infiltration of the laparoscopic port sites. Both techniques are currently being used in our hospital and a retrospective audit demonstrated better analgesia and lower consumption of morphine in the TAP block group.The differences were not statistically significant as the number patients in the audit were not large enough.The investigators are hoping that this study will demonstrate that the difference is real by recruiting the necessary number of patients into each group (36 per group)

Summary of Study Design The study will be a double blind randomised controlled trial with patients undergoing laparoscopic right hemicolectomy or laparoscopic high anterior resection randomly allocated into two groups, with the study group receiving bilateral TAP blocks followed by a morphine PCA and the control group receiving local anaesthetic infiltration of the laparoscopic port sites and specimen extraction site and a morphine PCA. A double blind design was chosen to eliminate patient and observer bias in reporting of pain scores. The presence of the control arm will ensure that any difference observed will be due to the effect of sensory nerve block due to the TAP block than due to the systemic effect of the injected local anaesthetic. The null hypothesis will be that there is no difference between the groups in the amount of morphine consumed by the patients during 48 hours after the operation. We chose this measurement as an objective but indirect measurement of efficacy of TAP block and pain relief thus received. Measurement of pain with various scoring methods are reliable only when concurrent reduction in consumption of pain killers are demonstrated. Recruitment and randomisation: All patients meeting the inclusion criteria will receive a patient information leaflet and an invitation letter to participate in the study during the pre-assessment visit. We aim to recruit 72 patients (36 patients per group). Informed consent will be taken by one of the investigators on the morning of the surgery, if the exclusion criteria are not applicable. Patients will be allotted consecutive participant numbers starting from one. Patients will be randomly allocated into either the study group and a control group. Randomisation will occur by using computer generated random numbers. Group allocation will be kept in a consecutively numbered, opaque, sealed envelope in the controlled drugs cupboard in theatre-6 anaesthetic room of Churchill hospital.Once patient has consented, the anaesthetist will open the corresponding numbered envelope and perform bilateral TAP blocks after induction of general anaesthesia, if the patient is in the study group the surgeons will infiltrate the port sites with local anaesthetic at the end of the procedure if the patient is in the control group. Blinding: The study group will receive bilateral TAP blocks with 20mls 0.25% bupivacaine on each side and the skin punctures on either sides will be covered with a small plaster. Patients in the control group will receive subcutaneous infiltration of the laparoscopic port sites and specimen extraction site with equivalent amount bupivacaine at the end of the procedure and small plasters will be stuck on either flanks approximately where the skin punctures for TAP block will be made. The assessor of pain scores and morphine doses (Recovery nurse \& Colo-rectal house officer) and the patient will be blinded to group allocation. Patient: Plasters will be stuck on flanks of all the patients both study and control group so that patient will not know if they have received TAP block. Recovery nurse: During handover to recovery the anaesthetist and scrub nurse will not mention about group allocation. Colo-rectal house officer: The house officers( Junior Doctors) who will be following up in the ward will not present in the operating theatre, so they will be blinded The study duration will be from induction of anaesthesia until the patients are medically fit for discharge from hospital. No extra visits other than routinely required for the surgical procedure is expected.