Lung And Heart-Lung Transplantation 
Lung transplantation presents special problems because of the risk of devastating infection in a transplanted organ that is continually exposed to nonsterile ambient air and dependent on the cough mechanism, which transplantation disrupts. Current 1-yr survival of lung transplant recipients is about 70% in a patient population that has essentially no chance of survival without transplantation. The long-term survival rate after lung transplantation is not fully established, but the incidence of graft loss late after transplantation appears to be lower than that of other organ allografts. Functional rehabilitation is good; most recipients resume everyday activities. Exercise capacity is slightly limited due to a hyperventilatory response.
Options for lung transplantation are single lung, double lung, or combined heart-lung transplantation. The former has been performed most often. Advantages of double lung and heart-lung transplantation are the removal of all potentially diseased tissue from the thorax and, for heart-lung transplantation, a more dependable healing of the tracheal anastomosis because coronary-bronchial collaterals are present within the heart-lung block. Disadvantages are the more extensive nature of the operations, with heart-lung replacement requiring cardiopulmonary bypass, the close match necessary for thoracic size, the use of two or three donor organs for one recipient, and, in some cases, the replacement of a normal heart with one that may develop posttransplant dysfunction. Indications for heart-lung transplantation are pulmonary vascular disease or diffuse parenchymal lung disease in which removal of all lung tissue is indicated (eg, certain cases of cystic fibrosis). When there is no intrinsic or secondary cardiac abnormality, the native heart of the heart-lung transplant recipient can be a donor organ for cardiac transplantation.
A single lung transplant is most clearly indicated for patients with restrictive lung disease. Advantages are the relative simplicity of the surgical procedure, which avoids systemic anticoagulation and cardiopulmonary bypass; the greater range acceptable for donor/recipient size match; and the optimal use of organs with the heart (and the contralateral lung) available for other recipients. Disadvantages include the possibility of ventilation/perfusion mismatch between the native and transplant lungs and poor healing of the bronchial anastomosis. Wrapping of the bronchial anastomosis with omentum has ameliorated but not eliminated the latter problem.
A double lung transplant removes all diseased lung tissue and theoretically is applicable in all patients who have no irreversible cardiac abnormality. However, division of the donor bronchial arteries and bronchocoronary collaterals makes tracheal healing problematic.
Donor selection and preservation: Cadaveric lung donors should be previous nonsmokers < 40 yr old. There should be minimal evidence of consolidation on chest x-ray, and ventilator-assisted oxygenation should be normal. Lung preservation is not well developed; a lung transplant must be performed swiftly. Most often, cold crystalloid solution containing prostacyclin is infused into the donor pulmonary arteries in situ before excision. Alternatively, the donor lung may be cooled systemically using cardiopulmonary bypass, avoiding the introduction of crystalloid into the pulmonary vasculature.
Transplantation procedure: For a single lung transplant, a lateral thoracotomy is used in the recipient. Cuffs of the pulmonary artery, pulmonary vein, and bronchus are used for anastomosis. If pulmonary artery clamping is not tolerated, bypass is required. A heart-lung transplant is performed on bypass through a median sternotomy with aortic and right atrial anastomoses. The tracheal anastomosis is carried out at a point immediately above the bifurcation. Double lung transplants require more elaborate surgical reconstruction of vessels and airways but have met with increasing success recently for patients whose hearts are normal.
Rejection management: Treatment is with corticosteroids given rapidly IV in high dosage, ATG, or OKT3. Prophylactic ALG or OKT3 is also frequently given during the first two posttransplant weeks. Acute rejection occurs in > 80% of patients but can be successfully managed in a very high percentage of cases. Lung rejection occurs more often than heart rejection in combined heart-lung transplant recipients, so that endomyocardial biopsies are not always helpful. Rejection is characterized by fever, dyspnea, and decreased SaO2 and forced expiratory volume in 1 sec (FEV1). The interstitial infiltrate seen on x-ray is hard to distinguish from that of an infection. Bronchoscopy with lavage and transbronchial biopsy are often used for diagnosis.
Complications: The most troublesome early complications are related to poor healing of the bronchial or tracheal anastomosis. Up to 20% of single-lung recipients develop bronchial stenosis, which can often be treated with dilation or stent placement. To prevent interference with healing of the bronchial anastomosis, corticosteroids are omitted from the immunosuppression regimen in the early postoperative period. Relatively high doses of cyclosporine (10 to 14 mg/kg/day po) and azathioprine (1.5 to 2.5 mg/kg/day po or IV) are used.
A late complication of lung transplantation is obliterative bronchiolitis causing slowly progressive airway obstruction. It may be a manifestation of chronic rejection. There is a decrease in FEV1 without evidence of any pulmonic process
