Evaluation of the Adjuvant Effect of Dexmedetomidine on Ropivacaine for Transversus Abdominis Plane Block in Inguinal Hernia Repair: A Prospective Double-Blind Randomized Trial

<b>Background and goal of study:</b> The aim of this double-blind randomized study was to investigate the efficacy of dexmedetomidine as an adjuvant to the local anesthetic in transversus abdominis plane (TAP) block for unilateral inguinal hernioplasty. <b>Materials and Methods:</b> Eighty eligible patients were randomly allocated into ultrasound-guided TAP block with either dexmedetomidine 0.5 mcg/kg diluted to a volume of 2 mL and ropivacaine 0.5% 25 mL (DR group) or ropivacaine 0.5% 25 mL and normal saline 2 mL (R group). The primary endpoint of this study was the numeric rating scale (NRS) score during coughing 24 h postoperatively. Secondary parameters were also evaluated. <b>Results:</b> Patients in the RD group demonstrated significantly less pain at rest three, six and 12 h postoperatively as compared to patients in the R group (<i>p</i> = 0.002, 0.032 and 0.049, respectively). Significant differences between the two groups were also demonstrated for NRS scores during coughing at 3, 6 and 12 h postoperatively (<i>p</i> = 0.013, 0.035 and 0.042, respectively). Additionally, the RD group demonstrated lower intraoperative remifentanil consumption (<i>p</i> < 0.001), lower PACU morphine requirement (<i>p</i> = 0.012) and lower overall PCA morphine requirement postoperatively (<i>p</i> < 0.001). Sedation scores, the incidence of hypotension, bradycardia and the occurrence of postoperative nausea and vomiting were no different between the two groups. Finally, the incidence of chronic pain at 6 months was significantly lower in the RD group compared to the R group (5.55% vs. 25%, <i>p</i> = 0.049). <b>Conclusions:</b> Dexmedetomidine as an adjuvant to ropivacaine reduces postoperative pain scores, has opioid-sparing effects and is associated with a favorable effect on chronic pain without side effects in patients subjected to TAP block for inguinal hernia repair.