Postoperative analgesia of continuous wound catheters and ultrasound guided rectus sheath catheters for colorectal surgery.

Group I: " Wound catheter continuous infusion group (CWCs) 30 patient": wound catheter was inserted before closure of wound. Technique: Two multi-orifice catheters were implanted by the surgeon into the subcutaneous layer on both sides of the surgical incision. The catheters were embedded into the wound to a length of approximately 6 - 10 cm and secured to the skin. A loading dose 10 mL of 0.25% bupivacaine was infused through each catheter just before closure of the incisional site. Analgesia was maintained by infusing 0.25% bupivacaine at a rate of 4 mL/h through two catheters (2 mL/hour per catheter) through electric infusion pump for 48 hours. Group II: "Rectus Sheath Catheters group (RSCs) 30 patient": Rectus sheath catheters were inserted bilaterally by the aid of ultrasonography at the end of surgery. Technique: The upper abdomen was prepared with 2% betadine, then the rectus muscle is imaged with a sheathed ultrasound probe in a longitudinal orientation above the level of the umbilicus. The probe was broadband (5-12MHz), 50 mm foot-print , linear array with an imaging depth of 4-6 cm. At first ultra-sonography probe identified the lina alba, then it was moved laterally to demonstrate the main body of the rectus abdominis muscle and the posterior rectus sheath, then 18G Tuohy needle was introduced few millimeters from the probe using an in plane technique at an angle of approximately 45 degrees to the skin just below the costal margin. The ultrasound allowed identification of the rectus muscle and posterior rectus sheath and fascia transversalis (two hyperechoic railway-like lines deep to it ). The needle tip was advanced to the desired position between the rectus muscle and the underlying posterior rectus sheath then 20 mL bupivacaine 0.25% (loading dose) were injected creating a space for the rectus sheath catheter to be introduced, causing hydro-dissection of the rectus muscle away from the posterior rectus sheath, and 4-8 cm of catheter was left in this space. The catheter depth at the skin is usually 12-15cm. To avoid interference with the surgical field the rest of the catheter was tunneled laterally. The same was repeated on the other side. Analgesia was maintained by injecting 10 ml bupivacaine 0.25% on each side every 6 h in the first 24 h postoperatively then every 12 h in the second 24 h to maintain analgesia. The catheters were removed after 48 hours post-operative.