Forty-eight-hr and 96-hr simple hypothermic preservations of the lung were studied on dogs using 4 kinds of solutions resembling extracellular electrolyte compositions (Epl-Ep4). The pH of each solution was changed from 6.377 to 7.463 by HPO42-/H2PO4- ratio. Twenty dogs were prepared as donors (12 for 48-hr preservation with Epl, Ep2 and Ep3, and 8 for 96-hr preservation with Ep3 and Ep4, respectively). The heart-lung block was removed from the donor, and flushed with 500 ml of preservation solution via the pulmonary artery, then immersed in the same cold (4°C) solution, after which it was stored in a cold (4°C) room. After preservation, the left lung was separated from the heart-lung block and was transplanted into the recipient orthotopically. The function of the transplanted lung was evaluated with serial x-ray findings, contralateral pulmonary artery ligation test, and histologic findings. In the case of 48-hr preservation, all of the four recipients with Ep3 (pH: 7.225) showed good aeration of the grafted lungs on the chest x-ray in the early postoperative period. As for the 96-hr preservation cases, one with Ep3 and three with Ep4 (pH: 7.463) presented good x-ray findings. Of these successful cases, seven dogs (5 of 48-hr preservation cases, 2 of 96-hr preservation cases) underwent contralateral pulmonary artery ligation 10 to 18 days after transplantation. Excluding one of the 96-hr preservation cases, six dogs tolerated this procedure. On histopathological examination of the successful cases, the 48-hr preservation cases showed almost normal pulmonary structure, while the 96-hr preservation cases showed slight degenerative changes in the alveolar walls. From the present study, it becomes apparent that clinical application of 48-hr preservation may be possible by using a phosphate buffered extracellular solution.
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