Objective:To evaluate the effect of intravenous infusion of lidocaine on pulmonary gas exchange function during acute lung injury in septic rats.Methods:Thirty clean-grade healthy male Sprague-Dawley rats, aged 2-3 months, weighing 220-280 g, were divided into 3 groups ( n=10 each) using a random number table method: control group (C group), sepsis group (S group) and lidocaine group (L group). Model of acute lung injury in septic rats was prepared by intraperitoneal injection of LPS 10 mg/kg in S and L groups, the equal volume of normal saline was injected in group C, lidocaine was injected at a loading dose of 10 mg/kg via the tail vein at 1 min after LPS injection and then continuously infused for 3 h at a rate of 10 mg·kg -1·h -1, and the equal volume of normal saline was given instead in C and S groups. Rats were sacrificed at 24 h after LPS injection, blood samples from the abdominal aorta were collected for blood gas analysis, and the oxygenation index (OI), alveolar-arterial oxygen difference (A-aDO 2) and respiratory index (RI) were calculated. Then the chest was immediately opened, and the left lung tissues were then immediately removed to determine the levels of tumor necrosis factor-α (TNF-α), heme oxygenase-1 (HO-1) and reactive oxygen species (ROS) (by enzyme-linked immunosorbent assay). The right upper lung tissues were removed for microscopic examination of the alveolar structure and pulmonary edema with a light microscope. The right lower lung tissues were also removed to observe the vascular endothelial structure with a transmission electron microscope. Results:Compared with group C, the levels of A-aDO 2, RI, TNF-α, HO-1 and ROS were significantly increased, the PaO 2 and OI were decreased ( P<0.05), and no significant change was found in PaCO 2 in group S and group L ( P>0.05). Compared with group S, the PaO 2, OI and HO-1 were significantly increased, the levels of A-aDO 2, RI, TNF-α and ROS were decreased ( P<0.05), and no significant change was found in PaCO 2 levels in group L ( P>0.05). The pathological damages of the lung tissues were significantly attenuated in group L when compared with group S. Conclusions:Intravenous infusion of lidocaine can improve pulmonary gas exchange function during acute lung injury in septic rats.