Ex-Vivo Perfusion of Limb Vascularized Composite Allotransplants: A Systematic Review of Published Protocols

Vascularized composite allotransplantation (VCA) has revolutionized restorative surgery of devastating injuries. Unfortunately, these grafts undergo significant injury during prolonged cold ischemia and subsequent reperfusion. Ex-vivo machine perfusion (EVMP) is a technique that has shown significant promise in solid organ transplant, but study of its utility in VCA has been limited. A systematic review was conducted to identify preclinical publications investigating perfusion in limb VCAs. Articles published through June 2023 were screened. 29 articles met inclusion criteria, comprising 370 VCA limbs from swine, rats, canines, and humans. EVMP was conducted under normothermic (n = 6), near-normothermic (n = 11), sub-normothermic (n = 3), or hypothermic (n = 13) conditions. While each study used a unique perfusate recipe, most were based on a premade medium. Many incorporated additives, including antibiotics and red blood cells. The duration varied from 3 to over 24 h. Multiple studies showed improved or equivalent biomarkers, histology, and outcomes for normothermic or near-normothermic EVMP (n = 4) and hypothermic EVMP (n = 8) compared to static cold storage, suggesting that EVMP may be a superior storage method to SCS. While there is no definitive evidence regarding the optimal temperature, perfusate composition, or perfusion time for VCAs, each perfusion factor should be chosen and adapted based on the individual goals of the study. This review offers a summary of the current literature to serve as an accessible reference for the design of future protocols in this field.