Development of an Extracorporeal Perfusion Device for Small Animal Free Flaps

BackgroundExtracorporeal perfusion (ECP) might prolong the vital storage capabilities of composite free flaps, potentially opening a wide range of clinical applications. Aim of the study was the development a validated low-cost extracorporeal perfusion model for further research in small animal free flaps.MethodsAfter establishing optimal perfusion settings, a specially designed extracorporeal perfusion system was evaluated during 8-hour perfusion of rat epigastric flaps followed by microvascular free flap transfer. Controls comprised sham-operation, ischemia and in vivo perfusion. Flaps and perfusate (diluted blood) were closely monitored by blood gas analysis, combined laser Doppler flowmetry and remission spectroscopy and Indocyanine-Green angiography. Evaluations were complemented by assessment of necrotic area and light microscopy at day 7.ResultsECP was established and maintained for 8 hours with constant potassium and pH levels. Subsequent flap transfer was successful. Notably, the rate of necrosis of extracorporeally perfused flaps (27%) was even lower than after in vivo perfusion (49%), although not statistically significant (P = 0,083). After sham-operation, only 6% of the total flap area became necrotic, while 8-hour ischemia led to total flap loss (98%). Angiographic and histological findings confirmed these observations.ConclusionsVital storage capabilities of microvascular flaps can be prolonged by temporary ECP. Our study provides important insights on the pathophysiological processes during extracorporeal tissue perfusion and provides a validated small animal perfusion model for further studies.

背景：体外灌注（Extracorporeal Perfusion, ECP）可延长复合游离皮瓣（composite free flaps）的活体储存能力，有望拓展其临床应用范围。本研究旨在开发一种经过验证的低成本体外灌注模型，用于小型动物游离皮瓣的后续研究。方法：在确定最优灌注参数后，对特制体外灌注系统进行评估：先对大鼠腹壁皮瓣进行8小时体外灌注，随后行显微游离皮瓣（microvascular free flap）移植。实验对照组设置为假手术组（sham-operation）、缺血组（ischemia）与体内灌注组（in vivo perfusion）。通过血气分析（blood gas analysis）、联合激光多普勒血流仪（laser Doppler flowmetry）与反射光谱法（remission spectroscopy）、吲哚菁绿血管造影术（Indocyanine-Green Angiography）对皮瓣及灌注液（perfusate，稀释血液）进行实时监测。在术后第7天，通过坏死面积评估与光学显微镜检查完成补充评估。结果：本研究成功建立并维持了8小时的体外灌注，期间钾离子浓度与pH值保持稳定。后续皮瓣移植手术均顺利完成。值得注意的是，体外灌注组皮瓣的坏死率（27%）甚至低于体内灌注组（49%），但该差异未达到统计学显著性（P=0.083）。假手术组仅6%的皮瓣区域发生坏死，而8小时缺血组的皮瓣坏死率高达98%。血管造影与组织学检查结果验证了上述观察结果。结论：临时体外灌注可延长显微游离皮瓣的活体储存能力。本研究为体外组织灌注过程中的病理生理机制提供了重要见解，并开发了一种经过验证的小型动物体外灌注模型，可供后续研究使用。