Abstract: Objective To explore the effect of preemptive analgesia with oxycodone on postoperative pain and immune function in patients undergoing video assisted thoracoscopic surgery (VATS). 
Methods A total of 80 patients classified by the American Association of Anesthesiologists as Grade Ⅰ-Ⅱ who planned to receive VATS under general anesthesia were selected, and randomly divided into the experimental group (n=40) and the control group (n=40). The experimental group received intravenous injection of 0.1 mg/kg oxycodone, while the control group received intravenous injection of 0.1 mg/kg physiological saline. The visual analog score (VAS) of pain, incidence of pain-related adverse events, incidence of postoperative pulmonary inflammation, postoperative awakening time, length of hospital stay, serum CD4+, CD8+, CD4+/CD8+ ratios, and tumor necrosis factor-α （TNF- α）,C-reactive protein (CRP) and c-Fos mRNA levels were compared between two groups. 
Results With the prolongation of time, the VAS scores of visceral pain and incision pain in both groups showed a gradually increasing trend. The VAS scores of visceral pain and incision pain in the experimental group were lower than those in the control group, and there was a statistically significant difference in the interaction between groups, time points, and time points between groups (P＜0.05). The incidence of postoperative nausea, restlessness during awakening, and pulmonary inflammation in the experimental group was lower than that in the control group, and the difference was statistically significant (P＜0.05). The CD4+ in both groups showed a gradual decreasing trend, with the experimental group showing a smaller decrease compared to the control group; there was a statistically significant difference in the interaction between groups, time points, and time points between groups (P＜0.05). The changes in CD8+ were not significant in the two groups, and the CD8+ in the experimental group was lower than that in the control group. There was a statistically significant difference in the interaction between groups, time points, and time points between groups (P＜0.05). The CD4+/CD8+ ratio in both groups showed a gradually increasing trend, and the CD4+/CD8+ ratio in the experimental group was greater than that in the control group. There was a statistically significant difference in the interaction between groups, time points, and time points between groups (P＜0.05). Both TNF-α and CRP levels showed a gradual upward trend in the two groups, and TNF-α and CRP levels were lower in the experimental group than in the control group; There was a statistically significant difference in the interaction between groups, time points, and time points between groups (P＜0.05). At 15-30 min after surgery, the serum c-Fos mRNA levels in the two groups were significantly higher than those before surgery, while the serum c-Fos mRNA levels in the experimental group were significantly lower than those in the control group, with a statistically significant difference (P＜0.05). 
Conclusion The regimen of preemptive analgesia with oxycodone can regulate the levels of pain stress response proteins after surgery in patients with VATS, reduce inflammatory reactions, and also reduce the ability of patients to undergo postoperative immune suppression caused by inflammatory reactions, which is beneficial for postoperative recovery.

Key words: thoracoscopy, oxycodone, analgesia