Evaluating the Adjuvant Effect of Dexamethasone to Ropivacaine in Transversus Abdominis Plane Block for Inguinal Hernia Repair and Spermatocelectomy: A Randomized Controlled Trial.

BACKGROUND: The transversus abdominis plane (TAP) block is a relatively straightforward regional technique used for postoperative analgesia in patients undergoing abdominal surgeries. Various adjuvants have been used in past to prolong the duration of action of analgesia in peripheral nerve blocks. Several studies investigating the analgesic efficacy of dexamethasone added to local anesthetic agents, such as bupivacaine, have shown promising results. However, there are few studies comparing the efficacy of dexamethasone with ropivacaine.

OBJECTIVES: To determine if the addition of dexamethasone 8 mg to ropivacaine 0.2% in a TAP block would prolong the analgesic effect when compared with ropivacaine 0.2% alone after inguinal hernia repair and spermatocelectomy.

STUDY DESIGN: A randomized, double blinded, placebo-controlled, prospective study.

SETTING: Teaching hospital.

METHODS: A total of 82 patients undergoing inguinal hernia repair or spermatocelectomy were enrolled in the study, of which 41 patients received TAP block with ropivacaine with saline, and the other 41 received ropivacaine with dexamethasone immediately following surgery. Both the proceduralist (resident) and the patient were blinded to the solution used. Visual analog pain scores (0 - 10) were obtained pre-block and immediately post block. Our primary endpoint was visual analog pain score at 12 hours, with 24 and 48-hour pain scores as the secondary endpoints.

RESULTS: The averaged pre-block pain score was 7.6 ± 1.7 in the saline group and 7.7 ± 2.2 in the dexamethasone group. There was an improvement in the pain scores from the baseline, at 12 hours after the administration of the block in both the groups. Although the dexamethasone group had a greater change in pain score (-3.2) than the saline group (-2.2), the difference between the 2 groups was not statistically significant (0.08). We did not observe significant differences in change from baseline at 24 hours and 48 hours between the 2 groups (P value = 0.74 and 0.44, respectively).

LIMITATIONS: We did not assess the total dose of analgesics used during the surgery with the assumption that the effect of intraoperative analgesics should wear off by the time we collect the 12-hour pain score. We did not control for the expertise of the provider that performed the block, as some of the providers may have been junior residents with limited experience and expertise in the area. Additionally, we were unable to include postoperative opioid consumption due to concerns of inconsistencies during patient reporting and data quality.

CONCLUSIONS: In conclusion, we could not show a statistically significant prolongation of analgesia for TAP blocks with ropivacaine when dexamethasone was added, though there was a one point drop in pain score at 12 hours post block when dexamethasone was added to the block solution. This decrease in pain scores at 12 hours may still be beneficial to patient satisfaction given the low side effect profile of dexamethasone. As ropivacaine has a lower pH than other local anesthetic agents, further well designed studies are needed to investigate the combination of this drug with more alkaline drugs like corticosteroids.

KEY WORDS: Regional anesthesia, transversus abdominis plane, dexamethasone, ropivacaine.