Retrospective Comparison of “Single” and “Double” Transversus Abdominis Plane Blocks for Intraoperative Anesthesia in Open Unilateral Inguinal Hernia Repair
Background: Transversus abdominis plane (TAP) and ilioinguinal/iliohypogastric (II/IH) nerve blocks have been described as analgesic adjuncts for inguinal hernia repair, but the efficacy of these techniques, individually or together, in providing intraoperative anesthesia is not known. We tested the hypothesis that the combination of TAP and II/IH (Double) would result in greater accordance between preoperative anesthetic plan and actual anesthetic technique provided when compared to TAP alone (Single).
Methods: With IRB approval and waiver of informed consent, we retrospectively reviewed the electronic medical records of consecutive unilateral open inguinal hernia cases performed by a single surgeon over 2 years. Patients who received a block for intraoperative analgesia were divided into Single or Double groups based on the regional anesthesia procedure notes. For the primary outcome, McNemar's test of paired proportions was used to compare actual anesthetic plan with preoperatively-documented anesthetic plan for each group. As a secondary subgroup analysis of patients who planned to receive Monitored Anesthesia Care (MAC) with block, log-linear analysis was used to identify factors associated with conversion to general anesthesia (GA).
Results: 187 open inguinal hernias were performed from October 2012 to July 2014. Based on inclusion/exclusion criteria, 51 patients with similar characteristics were included in analyses (32 Single and 19 Double). There was no difference in overall use of GA (Single=21/32 vs. Double=8/19; p=0.101). For Single, there was a statistically significant change in anesthetic plan preoperatively to intraoperatively (p=0.045) while there was no change for Double (p=0.564). Dose was an influencing factor with 3 of 4 MAC to GA conversions in the Single group associated with a lower, "analgesic" dose of local anesthetic. In contrast, 3 patients in the Double group who received the same “analgesic” dose successfully received MAC.
Conclusions: Offering both TAP and II/IH blocks for patients having open inguinal hernia surgery may ensure greater accordance between preoperative anesthetic plan and actual anesthetic technique provided. For TAP block anesthesia, higher doses of local anesthetic may be associated with lower likelihood of MAC to GA conversion unless both TAP and II/IH blocks are performed.