Evaluation of Techniques for Lung Transplantation Following Donation After Cardiac Death

Background: Lung transplantation using "donation after cardiac death" donors is a potential means to alleviate the shortage of suitable donor lungs for transplantation, but the practicality and utility of the various possible techniques need to be clarified. Methods: Using a dog model, we explored seven variations of standoff (ischemic) time (50 to 240 minutes), topical cooling (60 to 120 minutes), and flush cooling and cold storage (30 to 140 minutes) to mimic different human donor lung retrieval scenarios that can follow donation after cardiac death. The functional status of donation after cardiac death donor lungs was assessed initially with a 250 mL pulmonary arterial blood flush while ventilating with 100% oxygen and then on an ex-vivo perfusion rig for 120 minutes after retrieval. Results: All lungs achieved an excellent pO₂/FiO₂ ratio ranging from 472 to 586 with stable pulmonary artery pressures and pulmonary vascular resistance and no net weight gain (952 ± 221 g versus 1,006 ± 235 g) during the 120-minute evaluation period. Initial blood flush correlated well with measured perfusion rig pO₂ at 30 minutes (R² = 0.63). Conclusions: This canine study suggests that lungs donated after cardiac death are reproducibly useable for transplantation with ischemic times of as long as 60 minutes. Although more study is needed, a blood flush evaluation is simple and may have a role as a secondary allograft assessment tool. The existing techniques of donor lung evaluation and preservation after donation following cardiac death thus appear both feasible and practical.