CLoWI Versus PCA Morphine for Pain Control After Major Abdominal Surgery

Major intra-abdominal surgery represents one of the commonest groups of surgical procedures performed both worldwide and within Singapore. Common general surgical conditions requiring major intra-abdominal surgery include intestinal pathologies such as cancer, ischaemia, infection, haemorrhage and perforation.

Major surgery within the abdominal cavity is associated with significant complications which may be life threatening with an associated hospital mortality rate of as high as 20% for emergency surgery. Importantly, the recovery from this type of major surgery often entails significant pain and discomfort for the patient during healing of the abdominal wound and internal organs from tissue trauma associated with these surgical procedures.

Recent developments in major intra-abdominal surgery have demonstrated the importance of the early surgical recovery period where common postoperative complications including pain, chest infection, intestinal ileus and delerium are not only associated with prolonged hospital stay but are harbingers of poor long term surgical outcomes. Current recommendations for perioperative management of patients undergoing major intra-abdominal surgery stress the importance of high quality perioperative care to minimise these sequelae. Key features of these recommendations are to provide a pain free postoperative surgical recovery with minimal nausea and vomiting to facilitate early mobilisation and functional recovery from surgery.

Patient controlled analgesia (PCA) with opioids is the first line analgesia therapy currently used in the immediate post-operative period following major abdominal surgery. PCA with opioids has some inherent disadvantages that include side-effects of opioids such as nausea, vomiting, prolonged ileus, dizziness, hallucination and respiratory depression with the need for supplementary oxygen. This is most pertinent in elderly patients who are more prone to these side-effects in addition to being more likely to have difficulties in understanding how to use the PCA and so are more vulnerable to inadequate pain control. Consequently, there may be a delay in resuming mobility and discharge from hospital.

Continuous local wound infusion (CLoWI) with Ropivacaine that is delivered into the extraperitoneal plane via an ON-Q® (Halyard) infusion pump has been shown to be an effective analgesia post-operatively. The use of CLoWI negates the side-effects of opioids and furthermore, the small portable pump allows early ambulation with no requirement for supplementary oxygen. Previous published research has demonstrated the benefits of continuous local wound infusion with local anaesthesia in terms of postoperative analgesia and surgical recovery However, there are no randomized controlled trials comparing PCA versus continuous local wound infusion alone; this study will be the first randomised controlled trial to compare PCA (Morphine) with CLoWI-LA (Ropivacaine).

The local anaesthetic drug to be used for the wound infiltration system is Ropivacaine. Its mechanism of action involves inhibiting sodium influx through sodium-specific ion channels in the peripheral nerve axonal cell membrane, in particular, the voltage gated sodium channels. When the influx of sodium is interrupted, an action potential cannot arise and the conduction of a pain signal is inhibited. The local anaesthetic will be administered via 2 catheters that will be placed under direct vision by the surgeon at the time of wound closure.

Ropivacaine 0.5% will be infused at a rate of 4mls/hour (2mls/hour in each catheter) for a total of 4 days. It is currently in clinical use within our hospital as a routine method of providing postoperative analgesia following major abdominal surgery.