Abstract: AIM: To observe the effects of cyclooxygenase-2 (COX-2) inhibitors on the levels of inflammatory factors, nerve damage-related factors and antioxidant factors, as well as pain and delirium scores in the plasma of elderly patients with orthopaedic surgery, to clarify the role of COX-2 inhibitors in the prevention and treatment of POD and explore its possible mechanism.  METHODS: Eighty patients undergoing elective hip arthroplasty were randomly divided into parecoxib sodium group (P group, n=40) and control group (C group, n=40). Group C was injected with the same volume of normal saline at the same time point, and the preoperative cognitive function was screened 1 d (T0) before surgery by MMSE scale. The occurrence of POD was determined by CAM-CR scale score 1 d before operation (T0), 1 d after operation (T4), 3 d after operation (T6), 5 d after operation (T7). 1 d before surgery (T0), 12 h after surgery (T3), 1 d after surgery (T4), 2 d after surgery (T5). VAS scale score was used to observe the pain degree 30 min before anesthesia (T1), 1 h after surgery (T2), 1 d after surgery (T4). Central venous blood was collected from internal jugular vein 3 days after operation (T6), and the contents of inflammatory factors (IL-6 and IL-10) nerve injury related factors (S-100β protein, NSE, BDNF) and antioxidant factors (HO-1) were determined by ELISA.RESULTS: There were no significant differences in general condition, MMSE score and inflammatory factors, nerve damage-related factors and antioxidant factors between 2 groups at T1 (P>0.05). At T2 and T4, IL-6, S-100β and NSE in group P were lower than those in group C, while IL-10, BDNF and HO-1 were higher than those in group C (P<0.05). At T6, s-100 β and NSE in group P were lower than those in group C, BDNF was higher than those in group C (P<0.05), and there were no significant differences in IL-6, IL-10 and HO-1 between the two groups (P>0.05). There were no significant differences in VAS and CAM-Cr scores between the two groups at T0 (P>0.05). VAS score of group P was lower than that of group C at T3, T4 and T5 (P<0.05). At T4, T6 and T7, the CAM-CR score of P group was lower than that of C group, and the POD incidence of P group was lower than that of C group (P<0.05). CONCLUSION: COX-2 inhibitor (Parecoxib) can relieve postoperative pain in elderly patients, reduce postoperative plasma inflammatory factors and nerve injury related factors, increase antioxidant level and reduce the incidence of POD. The mechanism of POD reduction may be related to its anti-inflammatory, analgesic and antioxidant effects.

Key words: COX-2 inhibitor, Postoperative delirium, HO-1, Oxidative stress