Observation Of Acute Lung Injury After Aspiration Of Human's Gastric Juice In Rats

Objective The purpose of study was to effects of human's gastric juice(pH=2.3)in rats on aspiration acute lung injury, and to explore possible mechanism. Methods Twenty seven male rats were anesthetized and randomly divided into three groups of 9 each: in group A only incision of trachea and paracentesis of femoral artery/vein; in group B HCL (pH=2.3) was instilled into the lungs; in group C natural gastric juice (pH=2.3).The volume of fluid instilled into the lungs was 0.8ml/kg into group B and group C. PetCO2 and Respiratory Rate (RR)was supervised before and 30min, 1h, 2h, 3h and 4h after aspiration. The level of plasma IL-8 was measured at 1h and 4h after aspiration. And blood gas was measured at 4h after aspiration. The animals were killed 4h after aspiration. The wet/dry weight ratio of right intermediate lobe was measured,and the pathological changes of right lungs were observed at 4 hours after aspiration. Operating alveolar wash, LPI that the levels of total protein of bronchoalveolar lavage fluid (BALF) /serumal protein from left lung were calculated, and total WBC, PMN/WBC, MPO and the level of IL-8 in BLAF were detected. Results (1)Respiratory Rate increased dramatically in group B and C after aspiration(P<0.05),but PetCO2 remained in normal lever (P>0.05).(2)PaO2 decreased dramatically in group B and C, especially in group C (P<0.05). (3) Compared with group A , W/D ratio and total protein content in group B and group C were significantly raised And lung permeability index(LPI) was dramatically increased in group C (P<0.05). (4)The levels of IL-8 dramatically higher in plasma at 1h, 4h after aspiration and in BALF at 4h after aspiration than those in group A and in group B (P<0.05).Compared with group A, Total leukocyte was increased in group B and group C(P<0.05).And PMN/WBC and the levels of MPO in group C were higher than those in group A and group B (P<0.05). (5) In group C, the correlations between PMN/WBC and the levels of IL-8 in BALF and plasma at 4h after aspiration, contents of MPO in BLAF were 0.756,0.796,0.726 (P<0.05). (6)Light microscope examination: In group A there was no significant or slightly change, with a few neutrophils. In group C damages were most serious finding extensive morphologic lung damage: hemorrhage, edema, infiltration of PMN, proteinaceous exudates. Degree of injury in group B was less than that in group C. (7)Electron microscope observation: The continuities of capillary basement membrane in group C were abscised, the cells of capillary endothelium were swelling, endothelial cells'intercelluar space were widen, typeâ…¡alveolar cell microvilli were seriously destroyed and become fewer, even disappeared. Typeâ…¡alveolar cell laminated body were empty. The microstructure of group B was lightly destroyed and degree of injury was between group A and group C. Conclusion The damage after aspirating human's gastric juice was more serious than that of HCL (pH=2.3).To acute lung injury of aspirating gastric juice, IL-8, PMN and MPO were involved in inflammation, and Increased levels of MPO and IL-8 were responsible for function of PMN, this inflammatory reaction was more weighty than that after aspirating HCL.