Background Alleviation of microcirculation disorders in severe acute pancreatitis(SAP)can improve survival rates,and low molecular weight heparin(LMWH)is well known to have potent ameliorative effect On microcirculation disorders caused by anti-coagulant activity.The aim of this study was to investigate the effects of LMWH on pancreatic microcirculation in SAP in rats.Methods SD rats were randomly divided into 3 groups:sham operation(S)group,SAP group,and LMWH treatment (LT)group.The concentrations of serum amylase,tumor necrosis factor-alpha(TNF-α),endothelin-1(ET-1),pancreatic ultrastructure were examined at 24 hours after the models were set up in each group.Results Compared with S group,the concentration of serum amylase,ET-1,and TNF-α in SAP group were significantly increased(P<0.001);After LMWH treatment,the concentration of serum amylase,ET-1,TNF-α were decreased significantly compared with SAP group(P<0.001,0.01,0.001,respectively).On electron microscopy,the microthrombosis in LT group was significantly less than that in SAP group.The 3-day survival rate in SAP group(25.0%) was significantly lower than that in S group(100.0%,P<0.05)and in LT group(87.55,P<0.05).Conclusions The disorder of pancreatic microcirculation may be involved in the inflammatory response of rats with SAP.LMWH can effectively improve the survival rate of SAP,and alleviate the severity of microcirculation disorders through its antithrombin effects and down-regulate the levels of serum ET-1 and TNF-α.