University of Wisconsin solution for lung graft preservation: Which components are important?

Rat lung grafts were perfused with either Euro-Collins solution, University of Wisconsin solution, or one of six modified University of Wisconsin solutions that had been sequentially depleted of specific components (n = 5 each group). After storage at 4° C for 6 hours, the isolated, ventilated pulmonary graft was reperfused for 1 hour with recirculating venous blood from a support animal. In a further group, lungs were reperfused immediately after explantation to provide control values. Grafts flushed with University of Wisconsin solution functioned at control levels with regard to oxygen tension: University of Wisconsin solution 128 ± 2.7 mm Hg, control 126 ± 5 mm Hg; graft blood flow: University of Wisconsin solution 9.9 ± 0.4 ml/min, control 10.2 ± 0.8 ml/min; peak airway pressure: University of Wisconsin solution 17 ± 0.5 mm Hg, control 16.5 ± 0.6 mm Hg; and weight gain: University of Wisconsin solution 0.12 ± 0.1 gm, control 0.19 ± 0.13 gm. In contrast, lungs treated with Euro-Collins solution functioned less well: oxygen tension 54 ± 6 mm Hg, graft blood flow 3.5 ± 0.42 ml/min, peak airway pressure 35 ± 4 mm Hg, and weight gain 4.15 ± 0.5 gm (p <0.0001 all parameters). Sequential removal of hydroxyethyl starch, magnesium, allopurinol, adenosine, glutathione, and lactobionate from University of Wisconsin solution did not impair the efficacy of the solution. However, substitution of raffinose with glucose led to significantly impaired graft function: oxygen tension 69.6 ± 9.6 mm Hg, blood flow 6.48 ± 0.58 ml/min, peak airway pressure 25.2 ± 2.8 mm Hg and weight gain 2.11 ± 0.8 gm (p <0.001 all parameters), comparable with the Euro-Collins group. The major factor responsible for the efficacy of University of Wisconsin solution in lung graft preservation appears to be the impermeant trisaccharide raffinose.