Abstract: Objective To study the effect of dexmedetomidine combined with ropivacaine preemptive analgesia on the perioperative period pain control and serum prostaglandin E2（PGE2），β-endorphin（β-EP）in patients undergoing thoracotomy.
Methods 80 patients with thoracotomy in our hospital were randomly divided into observation group and control group，each group had 40 cases，they were anesthetized by paravertebral nerve block，the control group was given ropivacaine，the observation group was combined with dexmedetomidine，and the anesthesia induction，maintenance and postoperative analgesia were the same in two groups.The anesthesia effect between two groups were compared.
Results The dosage of fentanyl in the observation group was significantly less than that in the control group（P＜0.05）; the RS score of the observation group was lower than that of the control group at the time of extubation and after extubation 5 minutes（P＜0.05）; the VAS score，serum PGE2 and β - EP in the observation group were lower than that in the control group at after operation 2h，6h，12h and 24h（P＜0.05）.
Conclusion Dexmedetomidine combined with ropivacaine has satisfactory effect on perioperative period pain control of patients undergoing thoracotomy，which can avoid the increase of serum PGE2 and β-EP after craniotomy.

Key words: thoracotomy, dexmedetomidine, ropivacaine, preemptive analgesia