Abstract:Objective To observe the effects of combining intravenous pump infusion of different doses of dexmedetomidine on acute and chronic pain, sedation, analgesic use, and adverse drug reactions in patients undergoing ropivacaine caudal block anesthesia for anorectal surgery. Methods A total of 96 patients scheduled for elective anorectal surgery in the Department of Anorectal Surgery, Xi'an Affiliated Hospital of Shaanxi University of Chinese Medicine from July 2021 to July 2023 were selected. According to a random number table method, patients were divided into Group A (n=32), Group B (n=32), and Group C (n=32). All three groups underwent ultrasound- guided caudal block anesthesia. Group A received an intravenous pump infusion of 50 mL of 0.9% sodium chloride injection. Group B received an intravenous pump infusion of dexmedetomidine 0.5 μg/kg (diluted to 50 mL with 0.9% sodium chloride injection). Group C received an intravenous pump infusion of dexmedetomidine 1 μg/kg (diluted to 50 mL with 0.9% sodium chloride injection). The mean arterial pressure (MAP), heart rate, sedation status, and pain status at different time points were compared among the three groups. The use of analgesic drugs and adverse drug reactions were recorded. A 6-month postoperative follow-up was conducted to record the incidence of chronic post- surgical pain (CPSP). Results The time effect, between-group effect, and interaction effect on intraoperative MAP and heart rate levels at different time points were statistically significant in all three groups (P<0.01). Pairwise comparisons showed that the fluctuations in MAP and heart rate levels in Group C were smaller than those in Group A and Group B, respectively (P<0.05). The time effect, between-group effect, and interaction effect on postoperative Visual Analogue Scale (VAS) scores at rest and during movement were statistically significant in all three groups (P<0.01). The VAS scores of Group C were lower than those of Group A and Group B, respectively (P<0.05). The time effect, between- group effect, and interaction effect on postoperative Ramsay Sedation Scal (RSS) scores were statistically significant in all three groups (P<0.01). Pairwise comparisons showed that the RSS scores of Group C were higher than those of Group A and Group B, respectively (P<0.05). There was a statistically significant difference in the time to first postoperative analgesic administration among the three groups (P<0.05); Group C was superior to Group B and Group A (P<0.05), and Group B was superior to Group A (P<0.05). There was a significant difference in the number of postoperative analgesic administrations among the three groups (Z=33.912, P<0.01). No significant difference was observed in the total incidence of adverse drug reactions among Group A, Group B, and Group C [31.25% (10/32) vs 18.75% (6/32) vs 31.25% (10/32), χ²= 1.688, P=0.430]. There was a statistically significant difference in the incidence of CPSP at 6 months postoperatively among Group A, Group B, and Group C [19.35% (6/31) vs 3.13% (1/32) vs 0, χ²=9.915, P=0.007]. Compared with Group A, Group C had a lower incidence of CPSP (P<0.05). Conclusion Compared with a low dose, a high dose of dexmedetomidine combined with ropivacaine caudal block can maintain stability in MAP and heart rate levels during anorectal surgery better, provide better postoperative sedation, have a significant effect on postoperative acute pain, prolong postoperative analgesia duration, and result in less CPSP.