A study investigating whether the administration of local anaesthetic solution via an interpleural catheter improves pain relief after liver resection surgery

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It is not known from published data how to best provide postoperative pain relief for patients who undergo major liver surgery. Many institutions that specialise in hepatobiliary surgery like Austin Health use intravenous morphine in addition to regional techniques such as an epidural or an interpleural catheter to provide postoperative analgesia. Research however shows that after patients undergo major liver surgery, there are significant disturbances in the clotting system of the body. This may increase the risk of bleeding complications. For this reason many institutions now consider epidural catheters to be unsafe in this setting because of the increased risk of epidural haematoma with the devastating neurological complication of spinal cord compression and paraplegia. At Austin Health, the standard accepted practice in providing postoperative analgesia after liver surgery is intravenous morphine, either alone or in combination with an interpleural catheter. An interpleural catheter is a small tube that is placed between the linings layers of the lungs by the anaesthetist at the end of the operation. A solution of local anaesthetic is infused continuously into the interpleural space, which then numbs the nerves that supply the skin over the surgical wound, reducing postoperative pain. Interpleural catheters have been shown to be effective in the management of pain following thoracic and upper abdominal surgery with minimal risks. However, no study has investigated whether the routine use of interpleural catheters after liver surgery is advantageous over morphine alone. The theoretical advantages of using an interpleural catheter is that it may result in less morphine being used, thereby reducing morphine related complications such as respiratory depression, sedation, nausea, vomiting and itch. However an interpleural catheter may not improve pain at all, therefore its use may be an unnecessary intervention that can be associated with uncommon complications such as infection, local anaesthetic toxicity and rarely a punctured lung. These questions have never been investigated in any scientific way before; therefore this study will help answer these questions and make a valuable contribution to caring for patients undergoing liver surgery. The purpose of this study is to compare whether the use of an interpleural catheter together with morphine provides better postoperative pain relief than just morphine alone. The provision of postoperative analgesia and the management of the patient in the postoperative period will not be changed or modified in any way as per the current postoperative guidelines and practices for analgesia after liver surgery. Patients undergoing suitable liver surgery will be invited to participate in the study. They will be approached after consenting for surgery in the hepatobiliary or anaesthetic outpatient clinics. All patients will have a general anaesthetic and surgery performed according to the usual practice of their caring clinicians. All patients will receive intravenous morphine together with simple analgesic adjuvants such as paracetamol. This is standard practice at Austin for all patients undergoing liver resection. Consenting patients will then be randomised into 2 groups. One group will receive an interpleural catheter with an infusion of local anaesthetic solution, the other group will not. Both techniques are considered standard practice at many centers that specialise in hepatobiliary surgery, including Austin Health. The main study aim will be to collect data from the patient’s postoperative records and assess there level of pain and how much morphine each group uses. These are standard parameters and observations routinely recorded in the patients records. We will use standard statistical tests to analyse the differences between the two groups of patients. The primary end-point will be pain on movement during the first 24 postoperative hours. Other end points will be cumulative 24 hour morphine consumption, with sufficient subjects being enrolled to find a 25% difference in morphine use between the two groups. Other end-points to be measured at 6, 12, 24 and 48 hours and will include patient rated scores for pain, nausea and itchiness, nurse-rated sedation score, and cumulative morphine doses. These are standard parameters and observations recorded for all patients. Subjects will be asked to rate their satisfaction with their postoperative analgesia on a qualitative scale at the completion of the trial. All patients will be managed by the Austin Health acute pain service guidelines, in accordance with standard practices for morphine and interpleural catheter based regimes.

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