Abstract: Extended Normothermic Ex-Situ Limb Perfusion Preserves Limbs Viable and Functional Up to 44 Hours

Abstract

INTRODUCTION: Ischemia and reperfusion injury remains one of the major limiting factors for the success of both replantation and vascularized composite allotransplantation. Compared to cold storage of preserved/procured organs, normothermic ex-situ perfusion is a novel approach that prolongs viability of the limb by maintaining physiologic cellular metabolism avoiding the deleterious effects of both hypoxia and cooling. This study aims to develop an ex-situ normothermic limb perfusion protocol to preserve the viability and function of amputated limbs for over 24 hours. METHODS: A total of 23 swine limbs were perfused using an oxygenated colloid solution at 38°C containing washed RBCs. The first 13 limbs were used to optimize the perfusion protocol. The subsequent 5 limbs (Group A) were perfused for 12 hours and the following 5 (Group B) as long as muscle contractility/peripheral perfusion were present. Electrolytes were balanced by partial perfusate exchanges. Limb viability was compared in the 2 groups by muscle contractility, compartment pressure, tissue oxygen saturation, indocyanine green (ICG)-angiography and thermography. RESULTS: Perfused limbs were able to retain physiological parameters and function for 12 hours in group A and up to 44 (24–44) hours in group B. Limbs in group A had lower final weight increase (0.54%±0.07 VS 14.11%±16.27) (p=0.008) and compartment pressure compared to group B (16.23 ± 7.10 VS 24.75 ± 7.79) (p=0.175). Final myoglobin and CK mean values were lower in group A compared with group B (875 ± 291.4 ng/mL VS 1010.6 ± 323.6 ng/mL and 53344 ± 14850.34 U/L VS 71881 ± 20475 ng/mL). In group B thermography and tissue oxygen saturation were significantly higher than in group A (respectively 35.37 ± 0.69°C VS 33 ± 1.44°C (p0.01) and 69.31 ± 9.3% VS 58.69 ± 8.4% (p=0.048)). Contractility and ICG-angiography were comparable in the two groups. CONCLUSION: The normothermic perfusion protocol has the potential to significantly impact outcomes in limb replantation and transplantation. Our results suggest that limbs in the 12-hours perfusion group retain better physiologic parameters at the end-point. However, the continuous optimization of the protocol allowed to maintain limb’s function and preserved peripheral perfusion for up to 44 hours.