Abstract: Objective To evaluate the clinical analgesic effect of different doses of dexmedetomidine(DEX) mixed with ropivacaine in hip surgery in children.Method 60 children aged 2-8 years(inclusive) were selected with developmental dysplasia of the hip(DDH) diagnosed,who needed open reduction of hip joint and osteotomy of pelvis and femur.Ultrasonicguided lumbar plexus block combined with general anesthesia was used.According to the composition of local anesthetics,children were randomly divided into three groups:simple 0.2% ropivacaine group(R group),0.2% ropivacaine+0.5μg/kg DEX group(0.5DEX group) and 0.2% ropivacaine+1μg/kg DEX group(1DEX group).The dosage of sufentanil used during operation,the dosage of sufentanil used in Post anesthesia care unit(PACU),postoperative Children's Hospital of Eastern Ontario Pain Scale(CHEOPS),intraoperative hypotension,bradycardia,postoperative excessive sedation,nausea and vomiting were observed. Result There was no significant difference in general information,operation time,intraoperative bleeding volume and blood transfusion rate among the three groups（P>0.05）.The dosage of sufentanil used during operation and the scores of CHEOPS 12 and 24 hours after operation in 0.5DEX group and 1DEX group were significantly lower than those in R group(P<0.05),but there was no significant difference between the two DEX groups（P>0.05）.There was no significant difference in the dosage of sufentanil used in PACU,intraoperative hypotension,bradycardia,postoperative excessive sedation,nausea and vomiting among the three groups（P>0.05）.Conclusion A certain dose of DEX combined with ropivacaine for lumbar plexus block provides better postoperative analgesia than ropivacaine alone in children undergoing hip surgery,and there is no obvious dose dependent effect and no obvious side effects.

Key words: dexmedetomidine, lumbar plexus block, ultrasound guidance, children