Pilot: Intraoperative TAP Block and Post-operative Pain Control for Minimally Invasive Hysterectomy for Endometrial Cancer

Overview

Modern postoperative pain management aims to optimizing pain relief while minimizing opiate usage. While opiates are effective for pain relief, they result in common adverse effects such as nausea, constipation, and urinary retention, and most importantly present a long-term risk of abuse and dependency. Commonly used approaches include non-opiate pain medications such as acetominophen and non-steroidal anti-inflammatory agents, as well as regional nerve blocks such as epidurals. The transversus abdominis plane (TAP) block is a fascial plane block performed by injecting local anesthetic into the plane superficial to the transversus abdominis muscle where the anterior rami of the spinal nerves course to provide sensory innervation to the abdominal wall. The injections are generally placed either subcostally or at the midaxillary line bilaterally. The TAP block has been shown to be effective in reducing pain scores and opiate usage in some randomized studies but not others in patients undergoing various abdominal surgeries. There is great variation in method of administration, sites injected, and local anesthetics used, which may in part account for the heterogeneity of trial results.

The investigators believe that the disappointing results thus far with TAP blocks in minimally invasive hysterectomy may relate to several factors. A combination of short and long-acting anesthetic agents may provide the optimal analgesic effect. Large volumes of injection may promote spread of the anesthetics for better coverage, especially as long-acting agents are known to diffuse minimally. Lastly, multiple injections may provide better coverage of the nerves that innervate the abdominal wall. The investigators also believe that laparoscopic TAP blocks, administered by the surgeon, have advantages over the more commonly used ultrasound-guided approach typically performed by anesthesiologists. The laparoscopic approach is quick, on the order of a few minutes, whereas the ultrasound approach can be time-consuming. There is also less risk of visceral injury since the injection is performed under direct laparoscopic view. There are now 2 randomized studies suggesting that the laparoscopic approach is equivalent to the ultrasound approach. An additional potential reason why most studies have been negative is that patients undergoing minimally invasive hysterectomy do not generally experience severe pain, making it more difficult to demonstrate pain reduction with any given intervention. However, the studies to date do indicate that these patients experience moderate pain and do use opiates. An intervention that markedly reduces or even eliminates opiate use would be of potential benefit. The investigators have used a TAP block technique that is performed intraoperatively by the surgeon under direct laparoscopic view. The investigators use a mixture of plain and liposomal bupivacaine injected at multiple sites and in large volume to distribute the drugs widely, potentially resulting in longer and improved efficacy. This method has not been previously studied in a randomized trial. The investigators propose to demonstrate that this technique markedly decreases opiate usage and pain scores in patients undergoing minimally invasive hysterectomy.