The Effect Of Continuous Veno-venous Haemodiafiltration On Multiple Organ Functions And Soluble Mediators In A Canine Model For The Multiple Organ Dysfunction Syndrome

Objective : To find a standardized animal model that would accurately imitateclinical features of multiple organ dysfunction syndrome (MODS).Methods: The study was approved by the Animal Care and Use Committee of Xinjiang Medical University. After a 24 hour fast, 15 male beagle dogs weighting 14 to 16.3 kg were anesthetized intravenously with pentobarbital sodium (30mg/kg). Instrumentation was performed in a sterile fashion with animals fixed in the supine position. Each animal was intubated with a 9-F cuffed endotracheal tube and ventilated at a tidal volume of 15ml/kg, a respiratory rate between 20 and 25 breaths/min, a positive end-expiratory pressure level of 2～3cmH2O. A 5-F catheter with multiple holes was inserted into the right femoral artery and advanced into the abdominal aorta for measurement of arterial pressure. A 7-F polyvinyl chloride catheter was inserted into the left femoral vein for continuous infusion of pentobarbital at 2 to 4 mg/kg/h and sampling of blood. A 11-F pulmonary artery catheter sheath was inserted into the right femoral vein to provide vascular access for CVVHDF. A second 11-F pulmonary artery catheter sheath was inserted into the left jugular vein and provided the return limb of the veno-venous circuit. All catheters were placed by direct cutdown and the wounds closed surgically. All catheters were flushed with heparinized saline to prevent clotting. A 14-F silastic catheter was inserted suprapubically into the bladder. Body temperature was monitored by a rectal thermistor and kept constant around 38～39℃using a heating blanket.After line insertion, once the animals had been hemodynamically stable for 30 minutes (heart rate change and blood pressure change<10%), they were subjected to hemorrhagic shock plus resuscitation and endotoxiemia to set up MODS model. Hemorrhagic shock was produced according to the method of Wigger. The dogs underwent withdrawal of blood through the right femoral vein with a syringe. MAP maintained about 6.7～7.3kPa for an hour. Following an hour observation period, the animals were resuscitated with intravenous infusion of Ringer's solution at 2 times the shed blood volume and the shed blood to return the heart rate and blood pressure toward baseline values. After 12 hours of the resuscitation of hemorrhagic shock, Escherichia coli endotoxin (O111B4 lipopolysaccharide; Department of Microbiology, Second Military Medical University, Shanghai, China) was given via the femoral vein, in a dose of 1.5 mg/kg in 500 ml of normal saline infused over 12 hours. Symptoms and signs, survival rate, organ function parameters and pathological changes in main organs were observed in dogs.Results: The baseline mean values for MAP was 114.2±13.2 mmHg in MODS group. Note that MAP is lowest in animals receiving hemorrhagic shock, followed by a partial recovery during the next 12 hours. MAP after the start of endotoxin injection, in MODS group, was significantly lower than baseline. Mean PaO2 after the start of endotoxin injection was significantly lower than baseline. Mean PaCO2 at 21 and 24 hr after the start of endotoxin injection, in MODS group, was significantly higher than baseline.Plasma level of alanine aminotransferase(ALT)?aspartate aminotransferase(AST)?blood urea nitrogen(BUN) and creatinine(Cr) were increased and severe pathological lesions were observed in tissues of the liver and kidney .Conclusion: It was successful to reproduce the standard large animal model which was very similar in all respects to a delayed two phase MODS of human patients. The Effect of Continuous Veno-venous Haemodiafiltration on Major Organ Function and Histopathological Changes in a Canine Model for Multiple Organ Dysfunction SyndromeObjective: To study the influence of continuous veno-venous haemodiafiltration (CVVHDF) on major organ function and histopathological changes in MODS dogs.Methods : fifteen Beagle dogs were subjected to hemorrhagic shock plus resuscitation and endotoxemia to set up MODS model, then dogs were randomly divided into 2 groups: CVVHDF group (n=8) and MODS group without CVVHDF (n=7). CVVHDF was performed ahout 12 hours after endotoxin injection was finished in CVVHDF group. Blood samples were taken for evaluation of serum ALT, AST, Cr, BUN,LPS and blood gas. After a maximal observation period of 40 hours, animals were killed then liver and kidney were taken for pathologic observation.Results: The beneficial effect of CVVHDF on the hypotensive effect of MODS model, was particularly striking at 6h(T5), 9h(T6) and 12h(T7) after endotoxin injection (P<0.01). Mean PaO2 in CVVHDF groups at 3h(T4)?6h(T5)?9h(T6) and 12h(T7) after endotoxin injection was significantly higher than in MODS group(P<0.05). The levels of Cr, BUN and LPS were decreased significantly in the CVVHDF group compared with the MODS group (P<0.05). Different degrees of congestion?spotty and mass necrosis?bleeding and inflammatory cell infiltration were observed in the liver and kidney tissues.These changes were more severe in the MODS group than in the CVVHDF group.Conclusion: Our results suggest that treatment with CVVHDF effectively removed plasma LPS from the circulation, attenuated endotoxin-induced hypotension , improved arterial oxygenation and ameliorated morphologic changes of liver and kidney in dog MODS model. The Effect of Continuous Veno-venous Haemodiafiltration on Soluble Mediators in a Canine Model for the Multiple Organ Dysfunction SyndromeObjective: To study the influence of Continuous Veno-venous Haemodiafiltration (CVVHDF) on plasma cytokine levels in MODS dogs.Methods : fifteen Beagle dogs were subjected to hemorrhagic shock plus resuscitation and endotoxemia to set up MODS model, then dogs were randomly divided into 2 groups: CVVHDF group (n=8) and MODS group without CVVHDF (n=7). CVVHDF was performed ahout 12 hours after endotoxin injection was finished in CVVHDF group. Immunohistochemistry was performed to localise changes in expression of IL-6,IL-10 protein of kidney and liver tissues from dogs in MODS group and in CVVHDF group. Liver and kidney samples of the MODS and CVVHDF groups were immediately collected after the dogs were killed. Il-6 and IL-10 mRNA levels were quantified by semi-quantitative RT-PCR. IL-6 and IL-10 concentrations were measured by ELISA.Results: Serum levels of IL-6 and IL-10 were significantly decreased in the CVVHDF group at 3h(T4), 6h(T5), 9h(T6) and 12h(T7) after endotoxin injection (P<0.01), as compared with animals in the MODS group. IL-6 was detected in the ultrafiltrate, The sieving coefficients (SC) for IL-6 was 0.27±0.13. IL-10 could not be detected in the ultrafiltrate. Immunohistochemical analysis revealed the expression of IL-6 protein was lower and the expression of IL-10 protein was higher in kidney and liver tissues in the CVVHDF group compared with those in the MODS group. IL-6 mRNA levels in the MODS group were markedly higher than those in the normal control condition and the CVVHDF group (P<0.01). IL-10 mRNA levels in the CVVHDF group were statistically increased, as compared with those in the control condition and the MODS group (P<0.01)Conclusion: Our results suggest that treatment with CVVHDF effectively removed IL-6 and IL-10 from the circulation and potentially improved immunologic disorder, we postulated that there was a better clearance of IL-6 via the convective transport in CVVHDF. The removal of IL-10 by CVVHDF maybe predominantly due to adsorption rather than convective transport.