Few studies have investigated the depth of intraoperative analgesia with non-opioid anesthesia. This study evaluated whether opioid-free anesthesia can provide an effective analgesia-antinociception balance monitored by the / pain threshold index in laparoscopic radical colectomy.We enrolled 102 patients undergoing laparoscopic radical colectomy with general anesthesia. Participants were randomly allocated into two groups to receive opioid-free anesthesia (group OFA) with dexmedetomidine (loading dose with 0.6 μg·kg-1 for 10 min and then 0.5 μg·kg-1·h-1 continuous infusion) and sevoflurane plus bilateral paravertebral blockade (0.2 μg·kg-1 dexmedetomidine and 0.5% ropivacaine 15 ml per side) or opioid-based anesthesia (group OA) with remifentanil, sevoflurane, and bilateral paravertebral blockade (0.5% ropivacaine 15 ml per side). The primary outcome variable was pain intensity during the operation, as assessed by the pain threshold index with the multifunction combination monitor HXD- I. Results were analyzed using repeated measures analysis of variance and Student's t-test. The secondary outcomes were wavelet index, lactic levels, and blood glucose concentration during the operation. The visual analog scale (VAS), rescue analgesic consumption, and side-effects of opioids after surgery were further assessed.One hundred and one patients were included in the analysis. Analysis revealed that the intraoperative pain threshold index readings were not significantly different between the groups from incision to the end of the operation (P = 0.06). Furthermore, similar changes in the brain wavelet index readings were observed in the OFA and OA groups. There was no statistical difference in VAS scores between the groups (P > 0.05); however, non-opioid anesthesia did reduce the rescue analgesic consumption after operation (P < 0.05). In the OFA group, the blood glucose levels increased by 20% compared to baseline and were significantly higher than those in the OA group (P < 0.001). The incidences of postoperative nausea and vomiting, urine retention, intestinal paralysis and pruritus were not significantly different from those in the OA group (P > 0.05).This study suggests that compared to the opioid anesthesia regimen, our opioid-free anesthesia regimen achieved an equally effective intraoperative pain threshold index in laparoscopic radical colectomy. The incidence of opioid-related adverse reactions was not different between regimens, and intraoperative blood glucose levels were higher with opioid-free anesthesia.ChiCTR1900021223, 02/02/2019, Title: " Opioid-free anesthesia in laparoscopic surgery: a randomized controlled trial ". Website: hppts:// www.chictr.ogr.cn.© 2022. The Author(s).