Abstract: Objective To evaluate the effects of ketamine on perioperative serum cytokine levels in patients undergoing orthotopic liver transplantation (OLT). Methods Twenty patients undergoing OLT were randomly divided into ketamine group (n=10) and control group (n=10). Patients in ketamine group were given intravenous bolus injection of ketamine at 0.25 mg/kg followed by ketamine infusion at 0.5 mg·kg-1·h-1 until the end of operation except in the anhepatic phase, whereas the control group received saline of the same amount. Arterial blood samples were obtained at the start of surgery (T1), 5 min before the anhepatic phase (T2), 5 min before recirculation (T3), 15 and 60 min after recirculation (T4, T5), and 0, 4 and 24 h after operation (T6, T7, T8). Serum levels of tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6) and IL-10 were measured by ELISA. Results Serum TNF-α, IL-6 and IL-10 levels increased significantly during anhepatic phase as compared with the baseline level (T1) (P<0.05), and the changes were especially obvious in IL-6 and IL-10. The levels of the cytokines kept rising after recriculation and reached the peak level at T5(P<0.05), followed then by rapid decline and still maintaining higher levels than the preoperative ones 24 h after operation. The levels of TNF-α in ketamine group between T2 and T7 were significantly lower than that in the control group, and the IL-6 level between T2 and T5 were also significantly lower in ketamine group. Serum IL-10 level did not show any significant difference between the two groups. Conclusion Ischemia and reperfusion injury of the liver and surgical stress induce pro- and anti-inflammatory cytokine responses during liver transplantation, in which event IL-6 and IL-10 are more sensitive than TNF-α. Ketamine can inhibit the production of TNF-α and IL-6 but not IL-10.