Reduced-size lung transplantation from adult to neonatal sheep

Lung transplantation continues to be limited by donor availability. This shortage is particularly acute in the pediatric population. A model was developed in sheep to simulate human pulmonary transplantation from adults into newborns. Pulmonary allografts were performed in 8 neonatal lambs (less than 10 days old) weighing between 2.5 and 5 kg. Unrelated adult sheep donors were used (weighing 55 to 82 kg). The recipient body weight was approximately 6% that of the donor, but ranged from 4% to 8%. Ipsilateral or contralateral upper lobe allografts were used, although the latter required inversion prior to implantation. All venous anastomoses utilized left atrial cuffs. The pulmonary arterial and bronchial anastomoses were constructed end-to-end. Following implantation the lobes were further contoured to fit within the recipient hemithorax using a linear surgical stapler. Animals were immunosuppressed with cyclosporine. Two animals died 1 week postoperatively but the remaining six survived 1 to 5 months. Postoperative lung scans at 10 to 14 days confirmed satisfactory ventilation and perfusion of the allografts. All vascular anastomoses were intact at postmortem examination. Primary bronchial healing accomplished without an omental wrap. We conclude that successful lung transplantation can be performed from adult donors into neonatal recipients. Preservation of the maximal arterial and venous length during native pneumonectomy is essential to allow matching of the vascular cuffs. Short donor lobar bronchi may be responsible for the reliable primary healing. Improved immunosuppression will be required to assess long-term function and growth of these reduced-size allografts.