Donor Organ Selection

Donor lungs are scarce for pediatric lung recipients. No more that approximately 15% of cardiac donors are suitable lung donors, reflecting the pulmonary injury associated with brain death and resuscitation of an organ donor. A diagnosis of asthma or other pulmonary disease in the donor is a strong relative contraindication go lung donation. In addition to a chest x-ray without infiltrates, the suitable lung donor should have an arterial paO2 greater than 300 mmHg on an FIO2 of 1.0 plus PEEP 5cmH2). All prospective lung donors should undergo flexible bronchoscopy as part of the evaluation process. Bronchoscopic findings, which contraindicate lung donation, include evidence of gastric aspiration and significant amount of purulent secretions.

Appropriate donor-recipient size matching is very important. Using the chest x-ray, the vertical and transverse dimensions of the donor are matched as closely as possible to the recipient's. Donor lungs, which are a bit small, may be expected to expand to fill the hemithorax. Donor lungs which are a bit too large may be trimmed with a stapling device at the implantation procedure. Donor-recipient bronchial size matching seems more closely associated with height than weight, so most programs list recipients with a range of 3-4 inches above and below the height of the recipient.

The lung procurement operation is conducted as for adults. The volume of pulmoplegic solution administered is adjusted for the size of the donor in a dose of 40 ml/kg.

Recipient Procedure

Most pediatric lung transplant procedures are performed using cardiopulmo-nary bypass. Its use obviates the need for single lung ventilation which may be very difficult to achieve in children; small airways may make bronchial blockers and double lumen endotracheal tubes difficult or dangerous to use. In children with cystic fibrosis, thick and copious secretions may be impossible for the anesthesiologist to control. Therefore, the implantation procedure is usually more safely performed using cardiopulmonary bypass. Further, use of cardiopulmonary bypass permits irrigation of the open bronchus with antibiotic irrigation without cross-contamination of the contralateral lung.

A "clamshell" incision through the fourth or fifth intercostal space provides excellent surgical exposure to both pleural spaces, the mediastinal structures, and the heart should an intracardiac defect require correction. The aorta and right atrium are cannulated for initiation of cardiopulmonary bypass. Aprotinin should be used to decrease bleeding. As the pulmonary hilar structures are dissected, extreme care must be taken to avoid injury to the phrenic nerves. Once the diseased lungs are removed, the recipient's mainstem bronchi are irrigated with antibiotic irrigation containing an aminoglycoside.

The implantation procedure is performed as in adults. The left lung is usually transplanted first. Implantation of the left lung requires retraction of the heart toward the patient's right. Implantation of the left lung first permits the heart to recover from this while the right lung is implanted.

Three anastomoses are required to implant a lung: pulmonary vein, pulmonary artery, and bronchus. It is easiest to perform the pulmonary venous anastomosis first using a running 4-0 polypropylene suture. The bronchial anastomosis is performed next. Great care must be taken to cut the donor bronchus as short as possible: two cartilaginous rings above the bronchial bifurcation into upper and lower lobes. The membranous trachea is sewn with a running 4-0 polypropylene suture and the cartilaginous portion is sewn with interrupted figure-of-eight 4-0 sutures. Most pediatric bronchial anastomoses are performed in an end-to-end fashion. Should significant bronchial size disparity be found between the donor and recipient bronchi, a telescoping anastomosis may be performed. The pulmonary artery anastomosis is then performed, again with a running 4-0 suture. The right lung is then implanted in the same fashion.

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