Liver transplantation in rats using small-for-size grafts - A study of hemodynamic and morphological changes

Background: Damage to a small-for-size liver graft after reperfusion is fre quently observed but the mechanism of injury remains unclear. Hypothesis: Injury to a small-for-size liver graft is related to the change s of portal pressure and blood flow. Main Outcome Measures: Survival rates, portal hemodynamics, microcirculator y changes, and morphological changes (by light microscopy and electron micr oscopy). Setting: A rat model of nonarterialized orthotopic liver transplantation co mparing 2 groups of rats transplanted with whole grafts (100% of recipient liver weight) and small-for-size grafts (30% of recipient liver weight). Results: Median survival of the rats with small-for-size grafts was 30 hour s (range, 27-37 hours). During the first 15 minutes after reperfusion, mean arterial pressure of the small-for-size graft group was significantly lowe r than that of the whole graft group (10-minute: 100 vs 132 mm Hg, P=.04; 1 5-minute: 96 vs 127 mm Hg, P=.04). Portal pressure (in centimeters of water ) of the small-for-size graft group was significantly higher in the first 2 0 minutes after reperfusion than the level before the an- hepatic phase (5- minute: 15.1 vs 9.3, P=.02; 10-minute: 16.1 vs 9.3, P=.03; 15-minute, 13.5 vs 9.3, P=.03; 20-minute: 13.4 vs 9.3, P=.03) and was significantly higher than chat of the whole graft group in the first 10 minutes after reperfusio n (5-minute: 15.1 vs 9.6, P=.02; 10-minute: 16.1 vs 10.3, P=.04). Hepatic m icrocirculatory blood flow (in milliliters per minute per 100 g) was also s ignificantly higher in the small-for-size graft group during the first 40 m inutes after reperfusion (S-minute: 16.3 vs 9.3, P=.02; 10-minute: 14.9 vs 6.6, P=.02; 15-minute: 14.8 vs 5.5, P=.02; 20-minute: 13.1 vs 7.0, P=.02; 3 0-minute: 13.2 vs 8.8, P=.04; 40-minute: 14.6 vs 7.1, P=.02). Light and ele ctron microscopy showed normal morphological features of whole graft up to 24 hours after reperfusion. The small-for-size graft, however, showed sinus oidal congestion, tremendous swelling of mitochondria of hepatocytes, irreg ular large gap of sinusoidal lining cells, and collapse of the space of Dis se. Conclusions: In a rat model, the portal hemodynamic changes in small-for-si ze grafts are transient. Progressive damage of the graft may result from mi crocirculatory failure due to irreversible endothelial injury after reperfu sion.