Controlled reperfusion after lung ischemia: Implications for improved function after lung transplantation

Objectives: Despite improvements in organ preservation, reperfusion injury remains a major source of morbidity and mortality after lung transplantation. This pilot study was designed to investigate the effects of controlled reperfusion after lung ischemia. Methods: Twenty adult pigs underwent 2 hours of warm lung ischemia by crossclamping the left bronchus and pulmonary artery. In five (group 1), the clamp was simply removed at the end of ischemia (uncontrolled reperfusion). The 15 other pigs underwent modified reperfusion using blood from the femoral artery to perfuse the lung through the pulmonary artery (pressure 40 to 50 mm Hg) for 10 minutes before removing the pulmonary artery clamp. In five (group 2), the blood was mixed with crystalloid, resulting in a substrate-enriched, hypocalcemic, hyperosmolar, alkaline solution. In five (group 3), the blood was circulated through a leukocyte-depleting filter, and the last five (group 4) underwent reperfusion with both a modified solution and white blood cell filter. Lung function was assessed 60 minutes after reperfusion, and biopsy specimens were taken. Results: Controlled reperfusion with both a white blood cell filter and modified solution (group 4) completely eliminated the reperfusion injury that occurred with uncontrolled reperfusion (group 1), resulting in complete preservation of compliance (98% ± 1% vs 77% ± 1%; p < 0.001, and arterial/alveolar ratio (97% ± 2% vs 27% ± 2%; p < 0.001); no increase in pulmonary vascular resistance (106% ± 1% vs 198% ± 1%; p < 0.001); lowered tissue edema (82.1% ± 0.4% vs 84.3% ± 0.2%; p < 0.001), and myeloperoxidase activity (0.18 ± 0.02 vs 0.35 ± 0.02 δOD/min/mg protein; p < 0.001). In contrast, using either a white blood cell filter or modified solution separately improved but did not avoid the reperfusion injury, resulting in pulmonary function and tissue edema levels that were intermediate between group 1 (uncontrolled reperfusion) and group 4 (white blood cell filter and modified solution). Conclusion: After 2 hours of warm pulmonary ischemia, (1) a severe lung injury occurs after uncontrolled reperfusion, (2) controlled reperfusion with either a modified reperfusion solution or white blood cell filter limits, but does not avoid, a lung reperfusion injury, (3) reperfusion using both a modified reperfusate and white blood cell filter results in complete preservation of pulmonary function. We therefore believe surgeons should control the reperfusate after lung transplantation to improve postoperative pulmonary function.