Fig. 1

Lactic acid comparison between two groups with different infusion speeds of sufentanil (Red line: The infusion rate of sufentanil is less than 1.88 µg/kg h; Blue line: The infusion rate of sufentanil is greater than 1.88 µg/kg h). Blood lactate levels were measured at 10 min and 2 h, 4 h, and 8 h after surgery, we found that lactic acid values in both groups peaked at 4 h after surgery and then declined. The rate of lactic acid decline was significantly faster in the group with a higher sufentanil dosage than in the lower group. The difference was statistically significant (P < 0.05)