183Application of ultrasound-guided single caudal block in neonates : Objective To explore the application value of ultrasound-guided single caudal block in neonates. Methods 50 neonates with anal atresia were randomly divided into two groups: Group C and Group U. Single Caudal block was performed after general anesthesia iduced by sevoflurane in both groups.The rate of successful block, the time of block operation, the adjustment times of puncture and the rate of failure, the complications of block and the CRIES pain scores within 6 hours after the operation were recorded. Results Compared with group C, the rate of successful block was higher in group U (100% vs 84%, P<0.05), the times of puncture was lower in group U (1.48±0.51 vs 2.12±0.72, P < 0.001), but the time of block operation was longer in group U (3.23±0.84 vs 1.84±0.69, P < 0.001).The scores of the CRIES scale within 1 hour after surgery was lower (P<0.05).Conclusion Application of ultrasound-guided single caudal block in neonates can improve the success rate of block, reduce the times of puncture, and improve postoperative pain scores.