Acellular Vs.cellular Perfusates For Short-term Ex Vivo Lung Perfusion

Background and ObjectiveAfter decades of development,lung transplantation has become a common treatment for end-stage lung diseases.However,the shortage of donor lungs has not been improved.Meantime,a large number of marginal lungs are wasted because they cannot be effectively repaired and evaluated.This situation leads to the death of a large number of patients because they are unable to obtain suitable donor lungs.In order to save marginal lungs and improve the status of donor lung insufficiency,Ex Vivo Lung Perfusion technology came into being.In 2001,Professor Steen,a pioneer of Ex Vivo Lung Perfusion,first proposed an Ex Vivo Lung Perfusion strategy called "Lund Protocol".It has been widely used by the medical academic circles for reference,and some research groups have successively introduced "Toronto Protocol" and "OCS Protocol" which are differentfrom Lund protocol.Although there are many differences among the three protocols,the difference of perfusion fluid is currently the focus of debate,and whether red blood cells need to be added into the perfusion fluid has become the core issue.Lund protocol formulated by Steen team aims to simulate the physiological perfusion environment faced by donor lungs after lung transplantation in vitro as much as possible,so as to ensure a more comprehensive and authentic evaluation of lungs quality.Adding red blood cells to perfusion fluid is not only able to increase the similarity between lung perfusion in vitro and physiological perfusion in vivo,but also make the monitored blood gas results and perfusion parameters more accurate.In order to prolong the perfusion time and increase the chance of repair,the Toronto team removed the red blood cells in the perfusion fluid and believed that the red blood cells had potential hemolysis risk during the long-term perfusion,which would cause damage to the donor lungs.The "OCS Protocol " selected a perfusion solution similar to the "Lund Protocol" and achieved the same ideal perfusion effect.In order to determine the advantages and disadvantages of perfusion fluid,a 2-hour short-term perfusion strategy was adopted in this study to compare the effects of mixed whole blood perfusion fluid,mixed red blood cell perfusion fluid and cell-free perfusion fluid on donor lung quality after ex vivo lung perfusion,including differences in oxygenation function,anaerobic metabolism,pulmonary vascular resistance,pulmonary vasodilation function,lung compliance and pulmonary edema degree,in order to provide basis for improving short-term ex vivo lung perfusion strategy.MethodsFifteen donor pigs with an average weight of 30kg(27-33kg)were randomly assigned to the following three groups:(1)whole blood group,(2)RBC(red blood cell)group,(3)acellular group(n=5 in each group).Donor pigs received general anesthesia and median sternotomy,and blood was collected and donor lungs were removed.The blood collected in the red blood cell group was washed by the autotransfusion system to obtain concentrated red blood cells,and the blood collectedin the whole blood group was stored at low temperature without special treatment.Three groups of donor lungs were perfused with whole blood perfusate,red blood cell perfusate and cell-free perfusate respectively for 2 hours in vitro.Blood gas was measured at 0h,0.5h,1h and 1.5h respectively,and perfusion parameters were recorded at the same time.Stop mixing oxygen into the perfusion fluid at 1hour and50 minutes,and measure arterial blood gas and perfusion parameters after 10 minutes.Then add 0.5 ml,1ml and 2ml nitroglycerin into the perfusion liquid in turn.When the resistance curve was stable,recorded the corresponding perfusion parameters respectively.After perfusion,the dry and wet weights of the upper lobe of the left lungs were measured,in order to understand the degree of pulmonary edema of donor lungs,.Results1.Perfusion resistance: There was no statistical difference in perfusion resistance among the three groups(P >0.05),but there was a significant difference in perfusion resistance at different time points(P <0.05),and there was no difference in the trend of perfusion resistance among the three groups over time(P >0.05),showing an overall growth trend.2.Pulmonary vasodilation function: There was no significant effect on the rate of perfusion resistance decline among three groups(P >0.05),and the interaction between nitroglycerin dose and group had no significant effect on the decline rate of perfusion resistance(P >0.05).Therefore,it cannot be considered that there was statistical difference in pulmonary vasodilation function among the three groups.3.Lung compliance: There was no statistical difference in lung compliance among the three groups(P >0.05),and there was no statistical difference in lung compliance at different time points(P >0.05).4.Oxygenation function: After 2 hours of perfusion,there was no statistical difference between oxygenation index and p CO2 among the three groups(P >0.05).5.Anaerobic metabolism: There was no statistical difference in the decrease rate ofglucose concentration and the increase of lactic acid concentration per unit time among the three groups(P >0.05).Time had no significant effect on the decrease rate of glucose concentration(P > 0.05),but had a significant effect on the increase of lactic acid concentration(P <0.05).There was no difference in the trend of the increase in lactic acid concentration among the three groups over time(P >0.05),showing a trend of increase after decline.6.Degree of pulmonary edema: After 2 hours of perfusion,the wet-dry ratio of the three groups was statistically different(P <0.05).The pairwise comparison showed that the degree of wet-dry ratio in the whole blood group was lower than that in the RBC group(P <0.05)and the acellular group(P <0.05),while there was no statistical difference between the RBC group and the acellular group(P >0.05).ConclusionWe suggest short-term Ex Vivo lung perfusion strategy.Perfusion fluid containing whole blood is more suitable for short-term lung perfusion in vitro than RBC perfusion fluid and acellular perfusion fluid.The advantage of whole blood perfusion may be due to the positive effects of various hormones and other components in plasma.