Ischemia Time in Extremity Allotransplantation: A Comprehensive Review

In response to the widespread occurrence of limb loss and the transformative potential of extremity vascularized composite allotransplantation (VCA), we examine the impact of warm and cold ischemia duration on limb survival and functional recovery. Our insights into warm ischemia are largely derived from relevant literature on replantation and revascularization. Studies indicate that achieving reperfusion within 5 to 6 hours of warm ischemia is critical for limb survival, and within 3 hours for curbing significant functional deficits. For limbs preserved in static cold conditions, as is standard practice in VCA, reperfusion should be attained within 10 to 12 hours of cold ischemia. However, our analysis exposes a lack of data on extremity functional recovery following cold ischemia, particularly in humans or large animal models. This underscores a gap in the literature that could guide clinical ischemia management in VCA if addressed. We anticipate optimal functional recovery between 3 and 6 hours of cold ischemia, as supported by outcomes in rats. Prolonged ischemia times are also associated with graft rejection, posing unique challenges to VCA. Tissues exhibit diverse responses, with muscle and nerve being highly susceptible to ischemic damage, and skin acquiring heightened immunogenicity. Ischemia management emerges as a focus for future policy and research initiatives. On the horizon, exploring updated transplantation protocols, vascular shunts, stabilizing perfusion solutions, and subnormothermic machine perfusion could mitigate ischemic damage and enhance clinical outcomes in extremity VCA.