Background
Currently vascularized composite allografts (VCA) are cold preserved (4°C) until transplantation. This process is time limited, as the tissue has to be revascularized within 4–6 hours to minimize ischemia reperfusion (IR) injury. Normothermic perfusion was proposed as an alternative method of preservation in solid organ transplantation Method helps to avoid complications associated with cold preservation and maintains tissue viability without inducing IR injury Using this method, previous investigators demonstrated its potential to prolong swine forelimb allograft survival up to 24 hours (4,5) In this study, we aimed to test this system on human forearm allografts
Methods
Five human forearms were procured from brain-dead adult donors under tourniquet control. Following elbow disarticulation, the brachial artery was cannulated. The limb was flushed with heparinized saline and connected to a temperature controlled (30–33°C) ex situ perfusion system (Figure) for 24 hours. The perfusate consisted of plasma and red blood cells with a target hemoglobin (Hb) concentration of 4–6 g/dL. Muscle biopsies (flexor carpi radialis) were obtained at 0, 12, and 24 hours
Results
Average warm ischemia time was 76 minutes Average arterial systolic pressure was 93±2 mmHg, perfusion flow 310 ± 20 mL/min (∼6–8% of the donor’s estimated cardiac output), and vascular resistance 153 ± 16 mmHg/mL/min. Perfusate had an average pH of 743 ± 004 , pCO2 32 ± 1 mmHg, pO2 317 ± 18 mmHg, and Hb 48 ± 04 g/dL Electrolytes (sodium, potassium, chloride) remained within a physiologic range Lactate started to increase steadily throughout the experiment; however, neuromuscular electrical stimulation revealed ongoing contraction throughout the experiment H&E staining showed mild fatty infiltration on some myocytes at 24 hours There was minimal change in fiber size, likely due to variation in age and gender between donors Muscle architecture was preserved at the end of 24 hours perfusion
Conclusions
All limbs remained viable after 24 hours of near-normothermic ex situ perfusion as evidenced by ongoing neuromuscular stimulation While no assumptions can be drawn about the long-term function of the extremity, this approach could help extend VCA transplantation to a wider geographic area It also has the potential to circumvent complications associated with cold preservation.