| Objective:The purpose of the present study was to determine the effects of epinephrine on survival of a cross-area axial flap on the lower back of rat.We inducted epinephrine diluted with saline by 1:400 000 saturation to the right stem of the flap.The mechanism of delaying flap with epinephrine were approached to understand its effects on the whole delayed survival of skin flaps thoroughly so as to provide the rationale for its clinical use.Method :126 male Wister rats(supplied by Department of experimental animal in Nanhua University)weighing 220-250 grams were subdivided into three groups:delayed by operation( Group A),delayed by local iuducting epinephrine (Group B),control group dealed with inducting saline (Group C). Pentobarbital was injected intraperitoneally to anesthetize animal,with the dose of 45mg/kg.The flap was designed at the lower back of rat,with the size of 5cm×1cm,crossing the middle area for 2.5cm and including stem of iliac branch from iliolumbar artery.First,the superior and inferior extremity of flaps in Group A were discissioned as designed; the flap was left to the panniculus carefully lest the vessels were destroyed; then the flap was sutured where discissioned after hemostasis. In Group B, the flap was based on the left iliac branch,and the epinephrine diluted with saline by 1:400 000 saturation was inducted subcutaneouly nearby the right iliac branch,once a day.The flap in control group was dealed with saline at the stem.Next,the cross-area flap was left at the time formerly mentioned and sutured where discissioned, based on the left iliac branch. Flaps in each group delayed were cut at 1,3,7,14 days respectively to examine the survival area, the density of micrangium and quant of lactic acid ,the expression of VEGF and perfusing the body with the mixed liquor of gelatin and lead oxide, finally to compare the survival of the falps delayed by epinephrine with operation and discuss the mechanism.Results:1,By macroscopic observation,the flaps survived appeared soft,ruddy,bleeding when acupunctured; the necrosis appeared stiff, black, non-bleeding.7 days after the second operation, the necrosis areas in epinephrine-delayed group and surgical delay group was less than the control, dropsy of tissue was lighter,at the distant part.2,The longer of delaying time,the higher survival rate in epinephrine-delayed group and surgical delay group. Delaying for 7 days, the survival rate was 78.17±1.29%,78.82±1.36%respectively and in 14 days delayed group, the survival rate was 90.13±0.82%,91.42±1.53%.While in control group, the survival rate was no more than 50%.3,The median line of flap was dyed with Hematoxylin and eosin(HE).After delayed for 7days, the density of micrangium was increased in epinephrine-delayed group and surgical delay group, equally matched the 14 days delayed group and obviously higher than the control group.4,In surgical delay group, the quant of lactic acid increased peaking after delayed for 3 days,then fell-off. In epinephrine-delayed group, the quant of lactic acid was highest immediately after injection,then kept steady after 7-14days.5,Immunohistochemical staining demonstrated that there was flavo- granules and active expression of VEGF at the epidermis, the dermis, the hair-follicle, the sebaceous glands, the sweat gland, the fibroblast cell in epinephrine-delayed group and surgical delay group。While in the control group,the expression of VEGF was less active.6,In 14-delayed epinephrine group and surgical group,after perfusing the body with the mixed liquor of gelatin and lead oxide,we found that vasodilatation and ramus anastomoticus in median line area obviously ,but in the control group,there was little diversify. Conclusion: The experimental model was selected as cross-area axial flap on the lower back of rats. Epinephrine local injected repeatedly played the same part as operation in delaying flaps,which caused vasoconstriction,resulting in disorder of internal environment, ischemia and hypoxia,finally resulted in vasodilatation ,ramus anastomoticus in median line area and increasement of survival rate.
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