Homograft replacement of the trachea using immunosuppression.

The experiments were divided into three-ring and five-ring autografts and allografts. In the animals receiving allografts, the trachea was exchanged between paired animals which were preoperatively immunosuppressed with Imuran (azathioprine) and postoperatively given Decadron (dexamethasone). Seven of the 14 dogs receiving a three-ring allograft survived until put to death months after the operation. Postmortem examination demonstrated a patent airway, but the cartilaginous rings were absent and the proximal and distal suture lines were approximated. By contrast, none of the dogs receiving the five-ring allografts survived beyond 29 days. In all, the cartilage had disappeared and the intervening fibrous tissue had collapsed and constricted the airway. On the other hand, in animals in which the trachea was simply transected and resutured over an area of seven to ten rings, leaving membranous portion intact, the trachea was entirely normal when the animals were put to death. It is concluded that tracheal replacement with an allograft is not feasible, even with immunosuppression. It is the blood supply to the grafted segment which precludes success.