Maximal preservation time of tracheal allografts

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°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°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 < 0.0001) 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.