Efficacy of Transversus Abdominis Plane (TAP) Block Techniques: A Comparison Between Intraoperative Surgeon Administration by Direct Visualization vs Image Guided Administration by Anesthesiologist, a Prospective Randomized Controlled Trial

Purpose: To demonstrate that TAP blockade administered by the surgeon during surgery is as effective as when placed as a separate procedure by an anesthesiologist under ultrasound guidance by head to head randomized comparison controlling for medication, concentration volume and location.

Introduction:

The transversus abdominis plane (TAP) block is a regional anesthesia technique where local anesthetic is injected into the neurovascular plane between the transversus abdominis and internal oblique muscles. The ventral rami of the segmental thoracolumbar nerves course through the TAP before innervating the anterolateral abdominal wall. The TAP block has been shown to provide postoperative analgesia following abdominal surgery. Prospective randomized trials have demonstrated analgesic efficacy of TAP block and cadaveric studies have shown reliable dye spread from T9-L1 (iliac crest to the costal margin) , although the spread is dependent upon the technique of injection, single versus multiple injections. The TAP block is an intermuscular plane block i.e., needle placed in the plane between the internal oblique and transversus abdominis muscles. The sensory fibers located in this plane is too small to be visualized by ultrasound or localized by nerve stimulation. The TAP block may be performed in patients under general anesthesia since nerve localization is not necessary. This block has a number of advantages which include technical simplicity, high analgesic effectiveness, opioid sparing, long duration of effect, up to 36 hours, minimal side effects in comparison to that associated with neuraxial analgesia (e.g., hypotension, motor blockade). TAP block has successfully been incorporated in enhanced recovery after surgery (ERAS) protocols to reduce postoperative pain, reduce post op narcotic requirement, provide earlier return of bowel function and reduce length of stay. However multiple techniques for placement of the block have been described, in differing locations and with differing agents to analgesia after a variety of procedures. Historically the block has been placed based on anatomic land marks in the triangle of Petit guided by the sensation of the administrator. The safety and anatomic reliability of this approach has been questioned. Currently the block is frequently placed by an anesthesiologist under ultrasound guidance. Recently there have been published reports of surgeons placing TAP blocks intraoperatively guided by palpation and direct visualization, both open and with laparoscopic visualization . It is currently the practice in the division of colon and rectal surgery to use a standardized method for placing a TAP block after open and laparoscopic abdominal colon and rectal cases as part of our ERAS protocol requiring minimal time and cost limited to the cost of the medication. The authors hypothesize that TAP block administered by the surgeon is as effective as when administered by an anesthesiologist under ultrasonic guidance controlling for medication, volume, concentration and location of placement.

Methods: This study is a randomized trial with a placebo control arm to confirm effectiveness of the block its self, as TAP block is fully adopted as standard practice throughout abdominal surgery. Consecutive patients 18 years old or greater with intellectual capacity to consent, who are scheduled to undergo elective open or laparoscopic abdominal surgery by the division of colorectal surgery, will be offered inclusion in the study. Choice of open versus laparoscopic procedure is at surgeons discretion based on the patient's condition, diagnosis and best practice. Those patients whose procedure begins laparoscopically who require conversion to laparotomy will be noted and included in the open group. Exclusions will include patients who have allergies to the medications, patients with a preoperative addiction to narcotics or chronic pain syndromes requiring chronic medication, or whose anatomy or procedure precludes placement of the block.

Consenting patients will be randomized to receive administration of a TAP block either intraoperatively by the surgeon by direct palpation and/or visualization or by an anesthesiologist under ultrasound guidance. Secondary randomization will assign 1/4rd of both arms to receive placebo. In treatment arm cases Marcaine 0.25% with epinephrine 1:200,000 in a volume in ccs equal to the patients weight in Kg will be delivered. Those assigned to placebo will receive an equivalent volume of saline. In all cases the block will be placed at the conclusion of the case; for the surgeon, prior to closure of the abdomen, for the anesthesiologist after skin closure but prior to emergence from general anesthesia.