A new animal model for split liver transplantation using an infrahepatic IVC graft

Porcine partial liver transplantation: a novel model of the "small-for-size" liver graft

Increasing shortage of cadaveric grafts demands the utilization of living donor and split liver grafts. The purpose of this study was to 1) define the "small-for-size" graft in a pig liver transplant model 2) evaluate pathological changes associated with small-for-size liver transplantation. Pigs were divided into four groups based on the volume of transplanted liver: (a) control group (n=4), 100% liver volume (LV) (b) group I (n=8), 60% LV (c) group II (n=8), 30% LV (d) group III (n=15), 20% LV. Tacrolimus and methyl prednisone were administered as immunosuppression. Animals were followed for 5 days with daily serum biochemistry, liver biopsies on day 3 and 5 for light microscopy, and tissue levels of thymidine kinase (TK) and ornithine decarboxylase (ODC). Liver grafts were weighed pretransplant and at sacrifice. All the recipients of 100%, 60%, and 30% grafts survived. Transplantation of 20% grafts (group III) resulted in a 47% mortality rate. Group III animals showed significantly prolonged prothrombin times (p<0.05), elevated bilirubin levels (p<0.05), and ascites. The rate of regeneration, as indicated by TK activity and graft weight was inversely proportional to the size of the transplanted graft. The severity of the microvascular injury was inversely proportional to graft size and appeared to be the survival-limiting injury. Frank rupture of the sinusoidal lining, parenchymal hemorrhage, and portal vein injury were prominent in group III animals 1 hour following reperfusion. This study established a reproducible large animal model of partial liver grafting; it defined the small-for-size syndrome in this model and described the associated microvascular injury.

Oxygen consumption, lactate metabolism, and gastric intramucosal pH in an experimental liver transplantation model

OBJECTIVE

To assess the usefulness of measuring whole-body oxygen consumption (VO2), arterial lactate concentration, and gastric intramucosal pH (pHi) as parameters for evaluating hepatic graft viability in a model of experimental liver transplantation.

DESIGN

Experimental, prospective study.

SETTING

Hospital laboratory for experimental surgery.

SUBJECTS

Twenty-eight Landrace-Largewhite pigs: 14 donors and 14 recipients.

INTERVENTIONS

Orthotopic liver transplantation. Two groups were differentiated by graft preservation status: an optimal-graft group (group 1), which received donor livers that had been preserved in Collins solution at 4 degrees C for <4 hrs (n = 7), and an injured-graft group (group 2), which received donor livers that had been preserved in Collins solution at 4 degrees C for >24 hrs (n = 7).

MEASUREMENTS AND MAIN RESULTS

Hemodynamic parameters, variables related with systemic and hepatic oxygen and lactate metabolism, gastric pHi, and arterial pH were measured at two stages: a) preanhepatic stage; and b) neohepatic stage (60 mins after reperfusion). There were no differences in VO2 between graft groups or stages. In the neohepatic stage, hepatic oxygen extraction and lactate turnover were significantly higher in the optimal-graft group than in the injured-graft group. In the neohepatic stage, gastric pHi decreased significantly and arterial lactate concentrations increased significantly in both groups.

CONCLUSIONS

Changes in hepatic VO2 cannot be detected by VO2 measurements. Optimal-state grafts increased their lactate turnover as a result of substrate overload, but injured grafts did not. Therefore, the evolution of arterial lactate concentrations in the immediate postoperative period may be useful for the early evaluation of transplanted livers. Gastric pHi can be a useful measurement in the immediate posttransplantation period for differentiating between hyperlactacidemia produced by liver dysfunction (normal pHi) and hyperlactacidemia produced by lactate generation as a consequence of inadequate tissue oxygenation or of a mixed origin (abnormal pHi).