Protective Effect Of Vasoactive Drugs On Acute Lung Injury In Septic Shock Rabbits

Objective:This experiment established a rabbit model of septic shock. Part one:To investigate the early diagnostic markers and methods of septic shock with acute lung injury (ALI) and to evaluate the significance of surfactant protein A and surfactant protein D (SP-A and SP-D) in the early diagnosis of ALI. Part two:To evaluate the protective effects of dopamine and norepinephrine on the septic shock with acute lung injury and to explore the probable mechanism.Methods A cecal ligation and puncture procedure combined with intravenous injection of lipopolysaccharides was used to make the septic shock model,sixty three rabbits were randomly divided into 5 groups:sham operation group (group A, n=7), septic shock group (group B, n=14), dopamine treatment group (group C,n=14), norepinephrine treatment group (group D, n=14), dopamine combined with norepinephrine treatment group (group E, n=14).7 rabbits from each group were sacrificed 3 and 6 hours after septic shock, the concentration values of surfactant protein A and surfactant protein D (SP-A and SP-D) in plasma were tested by ELISA method and the morphological changes of lung tissue were performed at 3 and 6 hour. Mean arterial pressure (MAP) and heart rate (HR) were continuously recorded.Results 1.The blood pressure of all the treated rabbits falls shortly after the LPS injection and falls again after a short time going up. MAP goes down to 60% or below of the basic MAP in 2 hours, the models of septic shock in rabbits were established.2. The concentration values of SP-A and SP-D:The concentration values of SP-A and SP-D in each group were significantly increased than those in group A, (P<0.05). No significant differences in the concentration values of SP-A and SP-D in plasma were found between group B and C at 3 and 6 h, (P>0.05); in group D and E, the concentration values of SP-A and SP-D in plasma were significantly lower than those in group B at 3 h and 6 h (P<0.05).The morphological changes of lung tissue were lessened in group D and E than those in group B and C.3. Light microscopy:The alveolar structure disorder, the epithelial cells injury, the interstitial edema, a large number of inflammatory cells and red blood cells infiltration and the capillary expansion and congestion was observed in group B and C at 3 h and 6h; in addtion, the lesion of 6h is more severe than that of 3h; the injury of group C was little lessened than that in group B, and was significantly lessened in group D and E.4. Electron microscopy:In group B and C,the microvilli of type â…¡ alveolar epithelial cells irregularity and sparse was observed, and endoplasmic reticulum expanded significantly, most of mitochondria cristae disappeared and in empty bubble; the lamellar corpuscle burst, and serious degranulation; and karyopyknosis, karyorrhexis and karyolysis was observed in part of type â…¡ alveolar epithelial cells; in addtion, the lesion of 6h is more severe than that of 3h; the changes of type â…¡ alveolar epithelial cells were lessened in group D and E than those in group B and C.Conclusion The lung tissue were injured severely in septic shock model Norepinephrine can relieved the lesion of lung tissue and play a protective role.