[Effects of acute respiratory distress syndrome induced by endotoxin on the right ventricular function in rats].

OBJECTIVE: To explore the effect of acute respiratory distress syndrome (ARDS) induced by endotoxin on the right ventricular function in rats.

METHODS: Sixty male Sprague-Dawley (SD) rats were randomly divided into normal saline (NS) control group and lipopolysaccharide (LPS) model group with 30 rats in each group. The rat model of ARDS was reproduced by intratracheal instillation of LPS 10 mg/kg after tracheotomy, and the rats in NS control group was intratracheally given the same volume of NS instead of LPS. The survival of rats in each group was observed. Right ventricular function was evaluated by echocardiography at 6 hours and 12 hours after instillation of LPS or NS respectively. Then the rats were sacrificed by bloodletting, and the right heart and lung tissue were harvested. The lung wet/dry weight (W/D) ratio was assessed. The pathological changes in cardiopulmonary tissue in rats were observed with hematoxylin and eosin (HE) strain, and the pathological score of lung injury was calculated.

RESULTS: There was no animal death in NS control group. In LPS model group, there were 3 rats dead at 6 hours, and 4 dead at 12 hours. The pathological manifestations of lung injury were found at 6 hours after instillation of LPS, and the marked pathological changes of ARDS, such as atelectasis and hyaline membranes were observed at 12 hours. There was no obvious abnormality in the lung tissue of the NS control group. Compared with the NS control group, the 12-hour lung W/D ratio and the lung injury pathological score in the LPS model group were significantly increased (lung W/D ratio: 7.69±1.02 vs. 4.14±0.48, lung injury pathological score: 8.26±2.12 vs. 1.32±0.94, both P < 0.01). Echocardiography showed that the right heart function of rats was significantly abnormal with the prolongation of LPS induction time, which showed that pulmonary arterial diameter (PAD) and right ventricular diastolic diameter (RVDd) were increased, maximum blood flow velocity of pulmonary artery (PAVmax), maximum pulmonary artery pressure gradient (PAmaxPG), pulmonary artery acceleration time (PAAT) and tricuspid annular plane systolic excursion (TAPSE) were decreased, with significant differences at 12 hours as compared with those of NS normal group [PAD (mm): 2.84±0.31 vs. 2.11±0.37, RVDd (mm): 4.18±0.71 vs. 3.17±0.40, PAVmax (mm/s): 704.00±145.13 vs. 809.59±120.48, PAmaxPG (mmHg, 1 mmHg = 0.133 kPa): 2.07±0.88 vs. 2.73±0.76, PAAT (ms): 23.80±4.87 vs. 30.01±3.02, TAPSE (mm): 2.48±0.45 vs. 3.56±0.40, all P < 0.01]. Pathological examination showed that the cardiac tissue in the LPS model group showed disorder of myocardial cells and scattered inflammatory cells at 6 hours, and cardiomyocyte degeneration, structural destruction and inflammatory cells were found at 12 hours.

CONCLUSIONS: ARDS induced by instillation of LPS at 12 hours causes right ventricular dysfunction in rats.