Continuous Transversus Abdominis Plane (TAP) Block for Open Radical Prostatectomy. A Double Blind Randomized Study.

Open prostatectomy is a surgical procedure performed by urologists to excise the prostate. This is achieved by a 10-cm vertical incision starting below the umbilicus and reaching the pubic area. Patients are hospitalized for 3-4 days: one of the criteria for safe discharge includes Visual Analogue Scale (VAS) for pain below 3 at rest. For postoperative pain control, patients receive patient-controlled opioid analgesia (PCA) with morphine. The average amount of morphine used in the first 24 h varies between 30 and 50 mg. Although this technique is widely used, side effects (sedation, ileus, pruritus) are commonly encountered with opioid administration. Thus alternative analgesic techniques such as epidural analgesia and wound infiltration have been used with some success. However adverse events have also been reported with these techniques (lower limb motor block with epidural; infection wound infiltration).

In the last 10 years, a new technique, the transversus abdominis plane (TAP) block, which anesthetizes the thoracolumbar nerves (intercostal, subcostal and first lumbar nerves), has been described. The thoracolumbar nerves provide sensory innervation to the anterolateral abdominal wall. The traditional technique for TAP blocks is performed with a blunt needle in the Triangle of Petit. The latter is delineated caudally by the iliac crest, posteriorly by the latissimus muscle and anteriorly by the external oblique. Two distinct pops can be felt as the needle crosses the fascial extensions of the external oblique and the internal oblique muscle, respectively. Thus the second pop usually signifies that the needle tip has reached the TAP. Although the traditional technique has been used to provide postoperatively analgesia for bowel surgery, hysterectomy and Cesarian Section, the position of the Triangle of Petit varies greatly thus making it difficult to palpate in obese patients. In 2007, there was a study describing an ultrasound-guided technique for TAP blocks: these authors advocated using ultrasonography to locate the TAP along the mid-axillary line above the iliac crest. This ultrasound-guided technique has been subsequently used to provide postoperative analgesia for laparoscopic cholecystectomy, appendicectomy and Cesarian Section. This technique has been shown to spare opioids in the postoperative period therefore facilitating an accelerated discharge and superior pain relief.

In our institution, the TAP block, either as a single shot or as a continuous catheter infusion, is used for abdominal and urological surgery when epidural blockade is not feasible.