We previously reported that short oxygenated warm perfusion before cold storage (CS) had improved the graft viability of rat livers from donors after cardiac death (DCD). In this study, we investigated the effectiveness of short-term oxygenated subnormothermic perfusion for different durations after CS in a rat DCD model, and investigated the effects of 30-min subnormothermic perfusion for DCD livers in pigs.Methods
In Study 1: We used an isolated rat liver perfusion system. The grafts were retrieved from Wistar rats 30min after cardiac arrest (thoracotomy), preserved in CS for 6h, and perfused with oxygenated subnormothermic (23-26°C) Krebs-Henseleit buffer for different durations (0, 30, 60, and 90min). After that, 15min incubation at 23-26°C, the grafts were reperfused under normothermic condition for 60min as a model of liver transplantation (0, 30, 60, and 90min groups; n=5 in each). In Study 2, landrace pigs (25-30kg) were randomly allocated into three types of groups (n = 5 per group): heart-beating (HB) graft, transplanted after a 4-h period of cold storage (CS); DCD graft, retrieved 20min after apnea induced cardiac arrest (respiratory withdrawal) and transplanted after a 4-h period of CS; and subnormothermic ex vivo liver perfusion (SELP) graft, retrieved in the same manner as the DCD graft but perfused with a subnormothermic oxygenated Krebs-Henseleit buffer (21-25°C, 10-15cmH2O) for 30min in the simplified dripping manner, without a machine perfusion system, after the 4-h period of CS, and subsequently transplanted.Results
In Study 1, performing SELP groups significantly improved portal flow volume (P <0.05), and bile production (P <0.05), decreased liver enzymes (P <0.05), and increased tissue ATP (P <0.01) compared to DCD group. In the histological examinations, additional SELP ameliorated tissue deterioration, preserved the parenchymal structure, and decreased apoptosis compared to DCD group (P <0.01). In Study 2, the survival rate in the SELP group was significantly better than that in the DCD group (P = 0.0016). In the histological examination, preserved structure of the parenchyma was observed in the SELP group, and SELP significantly decreased apoptosis compared to DCD group (P <0.0001).Conclusion
Even 30min of subnormothermic perfusion after CS recovered DCD livers from ischemia-reperfusion injury and might improve the viability of the grafts. Although 30min SELP was not sufficient to improve the survival rate as a level of HB group and to prevent primary graft non-function completely, this simple technique has the potential to expand the donor liver pool.