The Application And Value Of TcPO₂ In Evaluating The Degree Of Lower Extremity Ischemia Reperfusion Injury Of Rabbits

Objective: In the model of rabbit ischemic reperfusion, variation in different periods of superoxide dismutase（SOD）, malondialdehyde（MDA） and pathological form, which combined transcutaneous oxygen pressure（TcPO₂） to clear the correlation between TcPO₂ and the previous three. Finally, we investigate the value of TcPO₂ in reflecting the degree of lower limb ischemia reperfusion injury. for the purpose of using TcPO₂ to inspect the degree of lower extremity ischemia reperfusion injury and providing laboratory basis.Materials and methods: The 24 New Zealand rabbits were randomly divided into 4 groups with 6 in each: sham group（ group A）.ischemia 4H observation group（group B）, group C as ischemia 6h observation group, D group is ischemia 8h observation group. Obtaining 2ml blood from auricular vein preoperatively, the right inguinal region skinned and attained value of TcPO₂ from quadriceps preoperatively, experimental group with inguinal incision method, exposing and separating the right femoral artery. microvascular clipping and make sure the distal segment of occlusion without beating, then suturing. retesting TcPO₂ values in the place. In the experimental group, we restored the blood supply at certain point, which resulted in ischemia reperfusion injury. 4H after the recover of the blood supply, TcPO₂ value was obtained at the same place with getting 2ml blood. The sham group only exposing femoral artery, obtaining 2ml blood after 12 H.Other interventional measures was same as experimental groups. All the animals were sacrificed and obtained ipsilateral femoral quadriceps muscle for pathological examination（HE stain）, venous blood centrifuged under 5000 rpm for 10 minutes at room temperature, ELISA was used to detect the SOD and MDA. Comparing the variation of TcPO₂ which obtained from different groups with SOD, MDA and the pathological examination results to get a comprehensive analysis in order to assure varieties of TcPO₂ in ischemia reperfusion injury.Results: With time extension, TcPO₂ in ischemic lower extremity reduced. In group B, the indexes compared with the preoperative ones decreasing significantly（P<0.05）.The observed value in group C was lower than that in group B（P<0.05）.When the period of ischemia lasts up to 8h, TcPO₂ reflect the microcirculation oxygen had nearly approached to the level where artery was completely blocked, but not equivalent. Except the sham group, The SOD and MDA in each group were significantly changed compared with the preoperative（P<0.05）.SOD in the group B was significantly reduced and the MDA was increased. TcPO₂ was positively correlated with SOD（r=0.820, P<0.05）, and negatively correlated with MDA（r=0.986,P<0.05）. Postoperative pathological examination showed skeletal muscle fiber morphology is normal in sham group. Cells in group B with mild swelling and degeneration. cytoplasm’s transparency were slightly increases. However, there is no obvious necrosis. the changes of cytoplasm’s transparency in group C were more obvious, with the cells’ size changes, morphological disorders, karyopyknosis, pyknosis, karyorrhexis. In the group D, the histological changes were more obvious, and the muscle fibers showed patchy necrosis. However, there was no significant change of laboratory indexes and pathological changes in the sham group. The area under the ROC curve of TcPO₂ was 0.993, and the diagnostic threshold should be selected at the level of 8.5mmHg for the sake of high specificity and sensitivity.Conclusion:1) TcPO₂ can quickly and accurately reflect the pathological changes of the skeletal muscle fibers in the process of ischemia reperfusion injury on lower extremity, besides the process is easy and non-invasive. 2) TcPO₂ can be used to evaluate the prognosis of lower extremity ischemia reperfusion injury in rabbits: TcPO₂ lower than 8.5mmHg may indicate the occurrence of irreversible cell damage.