Intervention Of Continuous Venovenous Hemodiafiltration On Endotoxin-induced Acute Lung Injury Of The Piglets

PrefaceAcute Lung Injury(ALI) and Acute Respiratory Distress Syndrome(ARDS),two intensive forms of hypoxemic respiratory failure,may be secondary to shock,trauma, sepsis,and so on.The mortality rate ranged from 40%to 70%.Continuous Blood Purification(CBP) is a medical technique,which was developed quickly in recent thirty years.Many results from researches supported that CBP can clean out inflammatory and anti-inflammatory cytokines,stabilize hemodynamics,and has effects on Multiple Organ Dysfunction(MODS).ObjectivesTo investigate if continuous venovenous hemodiafiltration(CVVHDF) can play a better effect on improving respiratory function,hemodynamics,Hematological parameters, cytokine releasing and pathological damages of the endotoxin-induced acute lung injury of the piglets.Methods:18 healthy piglets of either sex,8-10kg weight,were randomly divided into three groups:control group(n=6),heparin-intervened singly group(n=6) and CVVHDF-intervened group(n=6).All animals were anesthetized,intubated and mechanically ventilated in supine position.A number of physical parameters were documented after baseline observation,all the piglets were injected intravenously endotoxin(E.coli O11:B4) 0.15 mg/kg within 30 minutes.As soon as modified oxygenation index(PaO₂/FiO₂) was＜300 and Pulmonary compliance declined 30% from the baseline,the animals of CVVHDF-intervened group received CVVHDF and heparin intravenously continuously to keep active coagulation time(ACT) 180s-250s for six hours.The animals of heparin-intervened group received heparin intravenously to keep ACT 180s-250s.All the animals were monitored for six hours and then were killed with a bolus infusion of 10 ml KCL.Measurements of hemodynamics(HR, MABP,PCCI,SVRI,EVLWI);blood gas(PaO₂/FiO₂,P(A-a)O₂,PaCO₂);respiratory parameters(RR,Cdyn,Rrs) and cytokine levels(TNF-α,STNF-â…¡) were recorded at baseline(Ba),onset of ALI(A0h),two hours after ALI(A2h),four hours after ALI(A4h), six hours after ALI(A6h) respectively.Immediately after the animals were killed,one block(0.5-1cm³) of tissue in right low part of the lung was got to calculate wet-to-dry(W/D) lung weight measurement,a little block of tissue in the left low part of the lung was fixed by immersing into a 10%formaldehyde solution.Within two weeks,four blocks(0.5-1 cm³) including nondependent and dependent sites were obtained and embedded in paraffin,then cut into sections and were subsequently stained with hematoxylin and eosin.All the sections were examined in light microscopy and scored using a quantitative scoring system.Statistical analysis of the data was performed by using the Stata 7.0 software.Results1.Respiratory parameters:After endotoxin was given,the PaO₂/FiO₂ and dynamic lung compliance(Cdyn) of every group began to decrease gradually,but the breath rate(RR),Alveolar-toarterial oxygen difference(P(A-a)O₂) and respiratory way resistance(Rrs) increased. Every parameter did not vary statistically among three groups at baseline and onset of acute lung injury.Four hours later from the onset of the acute lung injury,RR and P(A-a)O₂ of CVVI-IDF-intervened group improved,the differences were significant statistically compared with the other two groups.After six hours,the PaO₂/FiO₂,Cdyn and Rrs of the CVVHDF-intervened group improved,the differences were significant statistically compared with the other two groups.There was no statistical difference between controlled group and heparin-intervened group.No statistical difference of PaCO₂ can be found among three groups during the experiment. 2.Hemodynamics parameters:When the endotoxin given,mean arterial blood pressure(MABP),pulse contour cardio output index(PCCI) of animals of every group decreased;heart rate(HR), systemic venous resistance index(SVRI),external venous lung water index(EVLWI) increased.Every parameter did not vary significantly among three groups at baseline and onset of acute lung injury.After four hours of the acute lung injury,SVRI,EV-LWI of CVVHDF-intervened group improved,compared with the other two groups,the difference was significant.After six hours of ALI,the HR,MABP,PCCI of the CVVHDF- intervened group improved,compared with the other two groups,the difference was significant.There was no significant difference between controlled group and heparin-intervened group.There was no significant vary of central venous pressure(CVP) among three groups during the course of the experiment.3.Hematological parameters:There were no statistical difference found in the results of leukocyte count, erythrocyte count,platelet count,activated partial thromboplastin time(APTT), prothrombin time(PT),fibrinogen(FIB),double-dimmer(D-D) at baseline and onset of ALI among three groups.When the ALI occurred,leukocyte count decreased,but increased four hours later, no difference was found among three groups.There was no significant difference of erythrocyte count at baseline,A0h,A2h, A4h,A6h among three groups.After ALI occurred,the platelet count decreased continuously,but there was no significant difference of platelet count at baseline,A0h,A2h,A4h,A6h among three groups.The PT values of three groups at A0h,A2h,A4h,A6h were longer than those at baseline.But there was no difference among three groups.The APTT values of three groups increased continuously.At A2h,A4h,A6h the APTT values of CVVHDF-intervened group were longer than those of the controlled group,the difference was significant.At A6h,the APTT values of heparin-intervened group were longer than those of the controlled group,the difference was significant. But there was no significant difference between heparin-intervened group and CVVHDF-intervened group.After ALI occurred,the Fib decreased continuously in controlled group.But the values of the other two groups decreased within two hours after ALI occurred,at A4h, the Fib values became improved,at A6h there were significant difference between not only CVVHDF- intervened group and controlled group but also heparin-intervened group and controlled group,but there was no difference between CVVHDF-intervened group and heparin-intervened group.After endotoxin given,the D-D values increased continuously of controlled group. The values of the other two groups also increased after endotoxin given,at A2h the D-D values became improved,there were significant difference between not only CVVHDF-intervened group and controlled group but also heparin-intervened group and controlled group,but there was no difference between CVVHDF-intervened group and heparin-intervened group.4.Cytokine levels:No significant difference of TNF-αand STNF-â…¡concentrations were found at baseline and onset of ALI among three groups.When the acute lung injury occurred, the blood concentrations of TNF-αand STNF-â…¡increased.After six hours of ALI the blood concentrations of TNF-αand STNF-â…¡of CVVHDF-intervened group improved. Difference were significant between CVVHDF-intervened group and controlled group; the same outcome between CVVHDF-intervened group and heparin-intervened group (P＜0.05),but no statistical difference was found between controlled group and heparin-intervened group.5.W/D:The W/D of the CVVHDF-intervened group was lower than that of controlled group and heparin-intervened group.The difference was significant statistically,but no statistical difference was found between controlled group and heparin-intervened group.6.Pathologic examination:Pulmonary vascular congestion,alveolar hemorrhage,atelectasis,edema,necrosis and inflammatory infiltration can be found in issues of every group.The damages of the controlled group and heparin-intervened group were more serious than CVVHDF-intervened group.There was reduction of Lung injury score of CVVHDF-intervened group compared with the other two groups.However,lung injury scores did not vary significant between controlled and heparin-intervened group.But there was a tendency to less hemorrhage and thrombokinesis in the heparin group.Conclusion:1) There are respiratory,hemodynamics,coagulation disturbance and cytokine releases in piglets with acute lung injury induced by endotoxin infusion venously.2) CVVHDF has a good effect on improving the oxygenation,respiratory mechanics, hemodynamics,and lessening the pathological damages of the lung,furthermore,it is not harmful to the coagulation status of the acute lung injured piglets.3) Using of heparin may improve the local coagulation status in the lung circulation, but does not improve the respiratory function and hemodynamics.