| Objective:Severe acute pancreatitis(SAP) is a kind of serious systemic disease,which with sudden onset,many complications,and high mortality(20-40%).The main reason is it can cause multiorgan distress syndrome(MODS) at the early stage,such as the failure of lung,kidney,heart and liver.Among them,acute lung injury(ALI) is the most common complication of SAP,a considerable number of patients may exacerbate into acute respiratory distress syndrome(ARDS),which is the major cause of death in the early stage of SAP.In this research we factitiously induced rats'SAP by animal experiment.Without any pretreatments on SAP rats,we investigated the incidence and degree of lung injury during the evolution process of SAP for clinical diagnosis and therapy.Methods:Healthy male Sprague-Dawley(SD) rats,with weight ranging from 250g to 300g,were randomly divided into eight groups,and every group had 30 rats.The SAP model was induced by retrograde infusion of biliopancreatic duct with 3.5% sodium taurocholate solution at 0.1ml/100g in SD rats.The sham operation group was only done exploratory laparotomy. 1,3,6,9,12,18 and 24 hours after modeled every rat was killed to be tested:2 ml blood was taken from the celiac artery to make blood gas analysis.5 ml blood was taken from heart to test the content of serum amylase and the concentration of protein.Took the pancreas and the superior lobe of right lung,the tissues were fixed with 10% fomaldehyde solution to be made paraffin wax slices.Took the middle lobe of right lung for measuring the lung wet/dry weight ratio.The inferior lobe of right lung was made to be homogenate to measure the myeloperoxidase(MPO) activity.Clamped the bronchus of the right lung,done bronchial intubation,infused 3 ml sterile saline into main bronchus, collected the irrigation solution to test the protein content. Results:The pathological chang and pathological damage score of pancreas:there was no chang in SO group.Interstitial edema,inflammatory cell infiltratiion,hemorrhage and necrosis were observed in SAP groups,and the injury became worse with time.The pathological damage score was increasing over time,the score of group SAP was obviously higher than group SO(P<0.05),and it was significantly different between each time point within SAP group(P<0.05).The pathological chang and pathological damage score of lung:there was no chang in SO group.Inflammatory cell infiltratiion,interstitial and alveolar edema,hemorrhage and necrosis were observed in SAP groups and the injury became worse with time.The pathological damage score was increasing over time,the score of group SAP was obviously higher than group SO(P<0.05),and it was significantly different between each time point within SAP group(P<0.05).The mortality of rats and the incidence of lung injury of each time point in SAP group:the incidences respectively were 0%,0%,6.7%,20.0%,40.0%,70.0% and 90%;the incidence of lung injury in group SAP 1 hour was 63.3%.Results of serum amylase:the concentration of serum amylase in group SO was (596.9±248.13)U/L. The results in SAP group was obviously higher with time,which were obviously higher than group SO(P<0.05),and it was significantly different between each time point within SAP groups except group 9h compared with12h(P<0.05).Results of artery blood gas analysis:postoperatively,the pressure of oxygen in SAP group was declining,except 1 hour of SAP group,there were statistical differences between SO group and SAP group(P<0.05).The pressure of carbon dioxide at 1h,3h,6h,9h and 12h after operation was decreasing,but at 18h and 24h it was increasing.Except 1 hour of SAP group,there were statistical differences between SO group and SAP group, the difference within 1h,3h,6h,9h and 12h of SAP group was statistically significant (P<0.05).The wet and dry weight ratio of lung:the ratio of group SO was (3.397±0.22);the ratios at 1h,3h,6h,9h,12h,18h and 24h after operation were decreasing,except 1 hour of SAP group,there were statistical differences between SO group and SAP groups. (P<0.05).Results of pulmonary permeability index:the result of SO group was (112.64±18.50);the results at 1h,3h,6h,9h,12h,18h and 24h after operation were gradually decreasing,the results of group SAP were obviously higher than group SO(P<0.05),and it was significantly different between each time point within SAP groups except group 18h compared with 24h(P<0.05).The activity of myeloperoxidase(MPO):the result of SO group was (7.08±1.34)μ/g,the results at 1h,3h,6h,9h,12h,18h and 24h after operation were decreasing,the results of group SAP were obviously higher than group SO(P<0.05),and it was significantly different between each time point within SAP groups(P<0.05).Correlation analysis:the pathological damage score of pancreas was positively correlated with the pathological damage score of lung(r=0.945,P<0.01),the activity of MPO of lung was positively correlated with the pathological damag score of lung (r=0.946,P<0.01),the wet and dry weight ratio of lung was positively correlated with the pathological damag score of lung (r=0.879,P<0.01),pulmonary permeability index was positively correlated with the pathological damag score of lung(r=﹣0.859,P<0.01)。Conclusions:1 In our investigation the incidence of lung injury in group SAP 1 hour was 63.3%,the mortality of rats in group SAP 24 hour had reached 90%,which responded the SAP feature of many complications and high mortality.2 The pathological damage score of pancreas was positively correlated with the pathological damage score of lung,in other words as the severe acute pancreatitis grew worse,the degree of lung injury of rats was gradually increasing.3 The MPO level of lung tissue was obviously rising after operation,and the activity of MPO of lung was positively correlated with the pathological damag score of lung,so,excessive activation and accumulation of neutrophilic in lung tissue is the important characteristics of APALI,the activity of MPO could accurately reflect the accumulation degree of neutrophils,could reflect the extent of the damage by tissue inflammation.4 The wet and dry weight ratio of lung and the pulmonary permeability index were important indicators which reflected the oedema,oozy and vascular permeability of lung,were sensitive and objective indexs of acute lung injury.5 In artery blood gas analysis,the pressure of oxygen in SAP group was progressively declining,corresponded the feature of obstinate hypoxemia of ALI,but early could not use it to assess the damage degree of lung and adjust the treatment.The pathophysiological variation of PaCO2 in the early stage of SAP was respiratory alkalosis,and in the advanced stage was respiratory acidosis.
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