Continuous Bupivacaine Infusion Following Colonic Surgery

Patients undergoing abdominal surgery will be randomized to one of two groups.

Group 1: Wound perfusion with bupivacaine, plus patient controlled analgesia (PCA)

Group 2: Wound perfusion with placebo solution (isotonic saline) plus patient controlled analgesia (PCA)

All patients will be premedicated with IV midazolam up to 5 mg. On arrival to the operating room, a fluid bolus of 10 ml/kg/h will be administered before induction of anesthesia.

Those randomized to local wound perfusion will receive the local anesthetic or placebo via the ON-Q pain management system. At the end of surgery a catheter will be positioned in the subcutaneous layer of the wound, leaving via a separate stab incision. The wound closure will then be completed.

A loading dose of local anesthetic solution, 20 ml lidocaine 1% plus 20 ml bupivacaine 0.5%, or, the same amount of placebo will be injected into the wound before the patient leaves the operating room. Thereafter bupivacaine 0.5% alone or placebo will be injected continuously into the wound at a flow rate of 2 ml/h for 24 hours.

Subcutaneous oxygen tension (PsqO2) will be evaluated intraoperatively with a polygraphic-type tissue oxygen sensor positioned within a subcutaneous, saline filled Silastic® tonometer inserted into the patients' upper arm after induction of anesthesia.

Postoperative pain relief will be maintained by patient-controlled analgesia (PCA) with morphine (2mg bolus, 6-minute lock-out) and with local anesthetic wound perfusion.

Patients will be given supplemental oxygen via a face mask at a rate of 2 L/min. Additional oxygen will be given as necessary to maintain an oxygen saturation > 95%.

An observer blinded to group assignment will perform all the postoperative evaluations.

Patient chart review will be undertaken to screen for evidence of surgical wound infection. The presence of infection will be determined by review of the attending surgeon's documentation in the patient's chart.