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Controlled Oxygenated Rewarming of Cold Stored Liver Grafts by Thermally Graduated Machine Perfusion Prior to Reperfusion

The quality of cold‐stored livers declines with the extension of ischemic time, increasing the risk of primary dys or nonfunction. A new concept to rescue preserved marginal liver grafts by gentle oxygenated warming‐up prior to blood reperfusion was investigated. Porcine livers were preserved by cold storage (CS) in modified HTK‐solution for 18 h. Some grafts were subsequently subjected to 90 min of controlled oxygenated rewarming (COR) by machine perfusion with gradual increase of perfusate temperature up to 20°C or simple oxygenated machine perfusion in hypothermia (HMP) or subnormothermia (SNP). Graft viability was assessed thereafter by 4 h of normothermic blood reperfusion ex vivo. Endischemic tissue energetics were significantly improved by COR or SNP and to a notably lesser extent by HMP. COR significantly reduced cellular enzyme loss, gene expression and perfusate activities of TNF‐alpha, radical mediated lipid peroxidation (LPO) and increase of portal vascular perfusion resistance upon reperfusion, while HMP or SNP were less protective. Only COR resulted in significantly more bile production than after CS. Histological injury score and caspase 3‐activation were significantly lower after COR than after CS. Oxygenated rewarming prior to reperfusion seems to be a promising technique to improve subsequent organ recovery upon reperfusion of long preserved liver grafts.