Introduction: The usefulness of hypothermic machine perfusion and normothermic machine perfusion as preservation methods prior to liver transplantation has been reported, but is controversial. We have reported the usefulness of subnormothermic ex vivo liver perfusion (SELP) at temperatures around 20℃ to 25℃, and recently we have examined the optimal conditions for perfusion time in subnormothermic oxygenated machine perfusion, but the comparison between subnormothermic machine perfusion and perfusion at other temperatures has not been examined. We evaluated organ status during machine perfusion in pigs, and investigated the optimal temperature.

Method: Ten F1 pigs (body weight: 27-32 kg) were induced to cardiac arrest by bilateral thoracotomy, and their livers were removed after 20 minutes of warm ischemia. The removed livers were kept cold for 2 hours and then perfused. Perfusion was performed for 120 minutes with oxygenated Krebs-Henseleit buffer using a machine (CMP-X07W, developed by Asahikawa Medical University and Chuo Seiko Co.), which is capable of monitoring portal and arterial pressure. The group was divided into two groups according to perfusion temperature: subnormothermic perfusion group (n=5) and hypothermic perfusion group (n=5). Bile production, liver enzymes, and inflammatory cytokines were measured and the sinusoidal space, using tissue specimens taken from liver grafts, was measured at 30, 60, 90, and 120 minutes after the start of perfusion.

Results: LDH was significantly lower in the hypothermic perfusion group than in the subnormothermic perfusion group at all times. AST, ALT and IL-1β were not significantly different. The hepatic sinusoidal space was significantly greater in the hypothermic perfusion group at 30 minutes. Bile production was significantly lower in the hypothermic perfusion group at all time points.

Conclusion: Although the superiority of subnormothermic perfusion over hypothermic perfusion could not be demonstrated in this investigation, the causal relationship between organ status during perfusion and reperfusion injury is still being elucidated and requires further investigation.