Comparison of efficacy and safety of lateral-to-medial continuous transversus abdominis plane block with thoracic epidural analgesia in patients undergoing abdominal surgery: A randomised, open-label feasibility study

BACKGROUND We recently described a lateral-to-medial approach for transversus abdominis plane (LM-TAP) block, which may permit preoperative initiation of the block. OBJECTIVE Our objective was to evaluate the feasibility of continuous LM-TAP blocks in clinical practice in comparison with thoracic epidural analgesia (TEA). DESIGN A randomised, open-label study. SETTING University Hospital, London Health Sciences Centre, London, Ontario, Canada from July 2008 to August 2012. PATIENTS Fifty adult patients undergoing open abdominal surgery via laparotomy were allocated randomly to receive preoperative catheter-congruent TEA or ultrasound-guided continuous bilateral LM-TAP block for 72 h postoperatively. Reasons for noninclusion were American Society of Anesthesiologists physical status more than 4, known allergy to study drugs, chronic pain/opioid dependence, spinal abnormalities or psychiatric illness. INTERVENTIONS In the TEA group (n=24), patient-controlled epidural analgesia was maintained using bupivacaine 0.1% with hydromorphone 10mgml1 after establishment of the initial block. In the LM-TAP group (n=26), ultrasoundguided LM-TAP catheters were inserted on each side preoperatively after a bolus of 30 ml of ropivacaine 0.5% (20 ml subcostal and 10 ml subumbilical injections on both sides). Analgesia was maintained with an infusion of ropivacaine 0.35% at a rate of 2 to 2.5 ml h^-1 through each catheter, along with rescue intravenous patient-controlled analgesia. MAIN OUTCOME MEASURES The primary outcome was pain score on coughing 24 h after the end of surgery. Secondary outcomes were pain scores from 24 to 72 h, intraoperative and postoperative opioid consumption, time to onset of bowel movement and side effect profiles. RESULTS Mean [95% confidence interval (95% CI)] pain scores at rest ranged from 1. 7 (0.9 to 2.5) to 2.3 (1.1 to 3.4) in TEA vs. 1.5 (0.7 to 2.2) to 2.2 (1.3 to 3.0) in LM-TAP (P=0.829). The dynamic pain scores ranged from 2.9 (1.5 to 4.4) to 3.8 (2.8 to 4.8) in TEA vs. 3.3 (2.4 to 4.3) to 3.8 (2.7 to 4.9) in LM-TAP (P=0.551). The variability in pain scores was lower in the LM-TAP group than in the TEA group in the first 24 h postoperatively. Patient satisfaction and other secondary outcomes were similar. CONCLUSION Continuous bilateral LM-TAP block can be initiated preoperatively and may provide comparable analgesia to TEA in patients undergoing laparotomy. CLINICAL TRIALS REGISTRY not registered because registration was not mandatory at the time of starting the trial.