The Influence Of Extracorporeal Membranous Oxygenation On Small Bowel From Porcine Controlled Donors After Cardiac Death And Early Allograft Function After Intestinal Transplantation

Currently,live donations,donors of brain death(DBD)and donors of cardiac death(DCD)are the three major sources of donor organs,and DCD is considered to be the most promising donor source among them.In recent years,with the rapid increase in the number of patients waiting small bowel transplantation,DBD has been difficult to meet the demand of clinical small bowel transplantation.So far,live donations can only be used for segmental intestinal transplantation,which has rarely been carried out at home and abroad.Therefore,DCD will be the major source of donor organs for intestinal transplantation.Moreover,controlled DCD(CDCD)as a subclass of DCD,with specific warm ischemia time and good maneuverability,has the potential to be the primary source of donor organs for intestinal transplantation.In contrast with liver and kidney,intestinal mucosa is extremely vulnerable to injury resulting from ischemia and ischaemia-reperfusion injury.DCD inevitably experiences warm ischemia,cold ischemia and ischemia-reperfusion injury stages.When the intestinal graft is harvested from DCD,the infectious-related mortality is higher and the absorptive function is lower.Therefore,seeking a method which can limit,correct or even reverse the injuries induced by warm ischaemia,has a vital significance to improve the prognosis of intestinal transplantation patients and broaden the resource of donor.In order to reduce warm ischaemia injury,satisfied results are obtained by means of protecting liver and kidney graft from DCD using extracorporeal membrane oxygenation(ECMO)in some transplantation centers at home and abroad.ECMO is a temporary artificial extracorporeal support of the respiratory system and/or cardiac system,which can directly oxygenate and remove carbon dioxide from blood and maintain organ perfusion effectively.Regional perfusion by ECMO is an emerging technique for improving the quality of grafts and expanding the donor pool from DCD.At present,ECMO has not been applied in the field of small bowel from DCD,which makes it necessary for us to carry further theoretic discussion.Therefore,to assess the effect of extracorporeal support on small bowel from DCD and intestinal function after transplantation,we firstly establish a porcine model of CDCD and investigate the changes of hemodynamics and arterial blood gas,and then establish the orthotopic segmental small bowel transplantation model.This research can provide the basis for the clinical application of ECMO in the field of small bowel transplantation and is significant to broaden the resource of intestinal donors.Part ? Establishment of a porcine model of controlled donors of cardiac deathObjectives:To establish a porcine model of controlled donors of cardiac death(CDCD)and investigate the changes of hemodynamics and arterial blood gas.Method:Ten domestic crossbred pigs were anesthetized and ventilated with 100%oxygen.Once all baseline data were taken,atracurium(lmg/kg)was administered and the ventilator was discontinued while the animal was under deep anesthesia to establish the porcine CDCD model.Meanwhile,heparin(150-200U/kg)was administered after discontinuation of the ventilator.The time to death and the changes of blood pressure,heart rate,average blood press and arterial blood gas were monistored every 5 minutes until cardiac death.Result:The time to death was approximately(17.4±3.37)min.Within 5 minutes of removal of the ventilator,there was a hyperdynamic period.Systolic blood pressure and heart rate quickly increased to 118.5±10.4 and 108.2±4.94 respectively.Then blood pressure,heart rate rapidly reduced until the heart cardiac arrest.Moreover,the PaO2 quickly dropped to 17.4±3.13 mmHg.The blood gases throughout the apneic time showed a rapid hypercapnia and acidosis.Conclusion:A new swine CDCD model,simulating three stages of "withdrawal of ventilation,systemic anticoagulation and determination of death",which can be used in studies related to organ transplantation was successfully established.Part ? The influence of extracorporeal membranous oxygenation on small bowel preservation in a porcine model of controlled donors after cardiac deathObjectives:To evaluate the effect of extracorporeal membranous oxygenation(ECMO)on the small bowel preservation in a porcine model of controlled donors after cardiac death(CDCD).Method:Thirty domestic crossbred donor pigs were divided in to 5 groups.The first group served as live donations(LD)group,the second group served as the DCD group,and the remaining three groups were submitted to different periods of normothermic extracorporeal support(1,3 and 5 hours).The changes of graft appearance and arterial blood gas during extracorporeal support were recorded.Pathology,electron microscope,energy metabolism,cell apoptosis and tight junction protein expression level of intestinal mucosa and the level of plasma i-FABP,D-lactic acid,IL-6 and TNF-a were evaluated in normal,cardiac death and at the end of extracorporeal support,respectively.Result:The normothermic extracorporeal support could quickly restore graft blood supply and oxygenation,correct hypoxemia and acidosis.One hour extracorporeal support could improve the energy status in intestine of DCD.Although the histologic damage and apoptosis of El group had no significant difference with those of LD and DCD groups(P>0.05)5 the level of intestinal mucosa tight junction protein were decreaseed(P<0.05),and plasma i-FABP,D-lactic acid,IL-6 and TNF-a were increased progressively(P<0.05).With the extension of extracorporeal support,the intestinal mucosa damage degree,intestinal permeability and inflammation were gradually increasing,and the content of ATP in intestinal mucosa reduced gradually.Conclusion:The normothermic extracorporeal support for 1 hour in DCD could improve the energy status in intestine,which may increase the viability of the bowel.However,the damage degree of intestinal mucosa was increased and the viability of small bowel also reduced gradually with the prolonging of support timePart ? The influence of extracorporeal membranous oxygenation on early allograft function after intestinal transplantation in a porcine modelStudy 3.1 Establishment of a porcine model of orthotopic segmental small bowel transplantationObjectives:To improve vascular reconstruction and partial surgical techniques,establish a porcine model of orthotopic segmental small bowel transplantation.Method:Fourteen domestic crossbred pigs were divided into half donors and half receptors.The superior mesenteric vessels were freed and the distal ileum was harvested as graft.After irrigation and preservation,the small bowel was transplanted by end to end anatomosis of the superior mesenteric arteries and veins,and then the intestinal continuity was restored through a side-to-end of 20 cm from the proximal graft and end-to-end of distal enteric anastomoses,with the proximal part of the graft brought out as a stoma for the purpose of graft monitoring.Result:There were '/cases of transplantation,6 of which succeeded with a success rate of 85.7%.The average time of donor operation was(100±9.4)min,and the time of recipient operationwas(172±23)min,the average warm ischemia time was(0.3±0.1)min,the average cold ischemia time was(96±10.8)min,the total time for vascular anastomosis was(27.6±2.8)min.Conclusion:It is an ideal pig model for certain investigating of small bowel preservation,with a higher success rate and fewer complications.Study3.2 The influence of extracorporeal membranous oxygenation on early allograft function after intestinal transplantationObjectives:To evaluate the effect of extracorporeal membranous oxygenation(ECMO)on early allograft function after intestinal transplantation.Method:Thirty domestic crossbred pigs underwent small bowel transplantation with the method of study I.The experiment designed the groups as part II.Pathology,electron microscope,energy metabolism,cell apoptosis and tight junction protein expression level of intestinal mucosa and the level of plasma i-FABP,D-lactic acid,endotoxin,IL-6 and TNF-a were evaluated according to the experimental protocol.To evaluate the intestinal absorption function,the D-xylose absorption test and maltose absorption test were performed at day 7 after the transplantation.Result:Among the groups underwent extracorporeal support,the histologic damage,apoptosis and plasma i-FABP,D-lactic acid,endotoxin,IL-6 and TNF-a of E1 group had no statistically significant differences with the LD group,but were obviously lower than those of DCD group(P<0.05)and the secondary was the E3 group.There were no significant differences between the E5 and DCD groups(P>0.05).In contrast with DCD group,the intestinal absorption function was improved significantly in E1 and E3 group(P<0.05),while the E5 group had no statistically significant differences with the DCD group(P>0.05).Conclusion:Extracorporeal support for short time played a protective role in the small bowel from DCD,of which 1 hour may be the best supporting time.The protective role of ECMO may be partially mediated by the activation of caspase-3 protein during ischemia reperfusion.No protective role for the graft was found for 5 hours of extracorporeal support.