Background: Our objective was to study the maximal preservation time of directly revascularized tracheal allografts in immunosuppressed piglets.
Methods: Donor grafts were flushed with Euro-Collins solution (65 mL/kg at 4 degrees C) by simultaneous inferior thyroid artery and bronchial artery perfusion through a 15-cm aortic segment and heterotopically implanted on their own vascular pedicle after 3 (group 1), 6 (group 2), 15 (group 3), and 24 (group 4) hours of static storage in Euro-Collins solution at 4 degrees C (n = 5 each). The animals were observed for 4 weeks after transplantation and then sacrificed. Histologic evaluation of the tracheal allografts was routinely done using specimens from open biopsies.
Results: The overall length of tracheal grafts was 12.4 +/- 0.6 cm, and this variable was not significantly different between the four groups. Graft exocrine (mucous secretion) function began 1.3 +/- 0.5 days after transplantation in groups 1 through 3 but was absent in all group 4 grafts (p < 0.0001). All grafts in groups 1 through 3 were viable at the time of sacrifice and showed little discernible intergroup and intragroup histologic and functional (tracheal smooth muscle contraction and relaxation) variations except for a significantly higher (p < 0.001) incidence of rejection in group 3 allografts. In contrast, all grafts in group 4 became completely necrotic 4 days after transplantation (p < 0.001) despite full patency of all the vascular anastomoses.
Conclusions: These results demonstrate that tracheal allografts may be safely preserved for as long as 15 hours and that longer periods of ischemia are likely to result in irreversible allograft damage.