The WIPPET Study

The aim of this study is to determine whether infiltration and then continuous infusion of the wound with local anaesthetic reduces pain after caesarean section. Secondary outcomes include the effect on the need for opioid pain killers (e.g. morphine) and recovery after caesarean section. Currently the common methods used for post-caesarean pain relief include opioid pain killers (intravenous and oral), non-steroidal anti-inflammatory drugs, paracetamol and epidural analgesia. Opioids have unwanted side effects such as drowsiness, nausea and vomiting, itchiness and constipation, and pass to the newborn in breast milk. Epidural analgesia requires an indwelling epidural catheter and has infection risks, as well as being labour intensive. Numerous studies have looked at the effectiveness of local anaesthetics administered by infiltration and/or infusion as a means of postoperative analgesia after abdominal surgery. Several demonstrated a clear benefit to this approach, while others found no advantage. Two studies of wound infusion following caesarean delivery showed a reduced need for opioid painkillers but the new local anaesthetic levobupivicaine has not yet been studied for wound infusion. Recently, two wound infusion catheters have been developed to aid local anaesthetic infusion to surgical wounds. Information on absorption of local anaesthetics into the blood after wound infiltration is limited. Bupivicaine is the most widely used local anaesthetic. A study determined venous bupivicaine levels follwing total abdominal field block but this regimen did not inlcude continuous infusion. The effects of repeated ropivacaine instillation into the wound has been assessed and unbound ropivacaine concentrations were below the toxic range, however accumulation was noted. An alternative to bupivucaine and ropivicaine is levobupivicaine which has a better side effect profile than bupivicaine. There is no information about its absortion after wound instillation. A second aim of this study would be to determine venous levobupivicaine concentraions resulting from wound infiltration and a 24 hour postoperative period of irrigation by infusing through a wound catheter.