Objective To investigate the efficacy and safety of caudal block combined with intravenous or caudal injection of dexamethasone for postoperative analgesia in patients with high anal fistula resection.

Methods A total of 63 patients undergoing high anal fistula resection were selected and randomly divided into group Ⅰ (intravenous dexamethasone+caudal block), group Ⅱ (caudal injection of dexamethasone+caudal block) and group Ⅲ (simple caudal block), with 21 cases in each group. Patients in group Ⅰ were injected 15 to 20 mL 0.5% ropivacaine intravenously and 5 mg dexamethasone intravenously; thosein the group Ⅱ were injected 15 to 20 mL 0.5% ropivacaine+dexamethasone 5 mg in sacral canal; those in the group Ⅲ were injected 15 to 20 mL 0.5% ropivacaine in sacral canal. Visual Analog Scale (VAS) was used to evaluate the degree of pain before anesthesia, immediately after the operation as well as 10, 20 minutes after the operation and immediately after the operation; the VAS scores of patients were compared at 2, 6, 12 and 24 h after leaving the room. The time of first use of parecoxib sodium and the number of users of parecoxib sodium and tramadol were recorded. The incidence of postoperative nausea and vomiting (PONV), urinary retention and hypotension were recorded.

Results There were no significant differences in VAS scores between the three groups before anesthesia, immediately after surgery as well as 10, 20 minutes after surgery and immediately after surgery (P>0.05). The VAS scores of the group Ⅲ were significantly higher than those of the groups Ⅰ and Ⅱ at 2 and 6 h after leaving the room (P < 0.05). The first use time of parecoxib sodium in the group Ⅲ was significantly shorter than that in the groups Ⅰ and Ⅱ (P < 0.05); the number of tramadol users in the group Ⅲ was significantly more than that in the groups Ⅰ and Ⅱ (P < 0.05). The incidence of PONV in the group Ⅲ was significantly higher than that in the group Ⅰ (P < 0.05). There were no significant differences in the incidence of urinary retention and hypotension among the three groups (P>0.05).

Conclusion Caudal block combined with intravenous or caudal injection of dexamethasone can enhance postoperative analgesia and prolong postoperative analgesia time in patients with high anal fistula resection. Cacral block combined with intravenous dexamethasone is more effective in preventing postoperative nausea and vomiting.