Predictive value of liver tissue flow in assessment of the viability of liver grafts after extended preservation in pigs

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Abstract
The crucial damage in cold storage of liver allografts is to the hepatic sinusoidal lining (microcirculation). Using different solutions, we studied whether determinations of graft tissue flow were valuable in estimating the viability of liver grafts. Twenty‐three pairs of female pigs underwent orthotopic liver transplantation and were assigned to five groups according to the cold preservation time or solutions used: in group I the liver grafts were stored in Euro‐Collins solution (EC) for 4 h (n = 3), in group II the grafts were stored in EC for 12 h (n = 5), in group HI the donor was pretreated with azathioprine (AZA), 1 mg/kg per day, orally (PO) for 3 days before harvesting and the graft was implanted after 12 h cold storage with EC (n = 6), in group IV the graft was stored in modified University of Wisconsin solution (mUW) for 4 h (n = 3), and in group V the graft was stored in mUW for 24 h (n = 6). Liver tissue blood flow (LTBF) was measured, using a laser doppler device, at 60 min after recirculation of the graft. In the case of EC preservation, LTBF (ml/100 g of liver tissue per min) correlated well with 4‐day survival: 21.2 ± 3.0 ml/100 g of tissue per min mean ± SD, in group I (3/3, 100%); 10.0 ± 2.8 ml/100 g of tissue per min in group II (0/5, 0%); and 19.1 ± 3.4 m1/100 g of tissue per min in group III (5/6, 83.3%) (P < 0.05, group II vs I and III). All grafts with LTBF of more than 15 ml/100 g tissue per min functioned well. However, changes in microcirculation of the mUW‐stored livers did not correlate with early function of the graft: 23.0 ± 2.3 m1/100 g of tissue per min in group IV (4‐day survival; 3 of 3, 100%) and 23.5 ± 9.1 m1/100 g of tissue per min in group V (0 of 6, 0%). This was accompanied by graft dehydration during storage and an increased number of erythrocytes in the hepatic sinusoids post‐recirculation. We concluded that assessment of liver tissue flow by LDF was very helpful and easy to apply in predicting liver graft failure in the case of preservation with Euro‐Collins solution. However, LTBF should be carefully evaluated as a marker of liver graft viability when the liver graft is preserved with mUW.