Phase IV Study of Postoperative Pain Management

Open abdominal hysterectomy is a common procedure performed for many benign and malignant gynaecological diseases and is associated with moderate to severe pain. Traditional methods for postoperative pain management include patient controlled intravenous analgesia (PCA) using morphine, epidural analgesia and spinal analgesia with opiates but recently, even local aesthetic (LA) has been used intra-abdominally and into the abdominal wall. Although epidural analgesia may be considered by some to be gold standard for pain relief following abdominal surgery, a recent publication and past experience over several years may question the use of invasive techniques for lower abdominal surgery. Thus, there is a trend towards movement from central blocks towards other non-invasive methods for pain relief.

PCA with morphine is now commonly used for management of pain following major surgery and compared to central blocks, has advantages in being relatively safe, easy to use and associated with a high degree of patient satisfaction. However, the large doses of morphine necessary to ensure adequate postoperative analgesia means that side effects such as postoperative nausea and vomiting (PONV), tiredness, pruritus, headache and constipation may be a major problem in this group of patients. Therefore, alternative techniques to reduce morphine requirements are increasingly being used. These include the use of paracetamol, non-steroidal anti-inflammatory drugs (NSAID) and recently local anaesthetics (LA). The latter have been found to result in morphine sparing by 30 - 40 % and even a reduction in postoperative nausea (PON). LA infused intraperitoneally is safe and effective and a recent study showed that using 12.5 mg/h levobupivacaine could attain adequate analgesia. Thus, efficacy of LA has been established as well as the dose. However, the method of administration of LA intraperitoneally remains unclear.

This study is designed with the primary aim of studying whether morphine consumption can be reduced postoperatively using the patient-controlled administration system for intraperitoneal LA compared to a continuous infusion, and whether this translates into improved recovery parameters or reduced side effects and improved patient satisfaction.