Effect of donor pre-mortem hypoxia and hypotension on graft function and start of warm ischemia in donation after cardiac death lung transplantation

Background: The start of warm ischemic time (WIT) of donor lungs in donation after cardiac death (DCD) is not clearly defined. We investigated the effect of donor pre-mortem hypotension and hypoxia to determine which physiologic factor is the determinant of WIT onset in controlled DCD lung transplantation. Methods: Twenty mechanically-ventilated donor pigs were placed in 4 groups (n = 5 each) and exposed to each of the pseudo-agonal conditions for 60 minutes: (1) control group, no intervention and optimum ventilation, followed by cardiac arrest; (2) hypotension (HT) group, controlled cardiac tamponade reducing systolic blood pressure to <50 mm Hg, followed by cardiac arrest; (3) hypoventilation (HV) group, ventilation with room air at 5 breaths/min, followed by cardiac arrest; (4) non-circulation (NC) group, initial cardiac arrest, followed by a 60-minute standoff time. The lung graft was retrieved and the left lung was transplanted to the recipient. Graft function was evaluated for 4 hours after contralateral pulmonary artery ligation. The reperfusion injury was evaluated based on tissue cytokine expression, wet weight-to-dry weight ratio, and histology at the end of the reperfusion period. Results: Impaired post-transplant graft function was seen in the HV group, which had significantly poorer oxygenation during the reperfusion period than the other groups (p < 0.001). The HV group also had higher tissue levels of interleukin-8 (p < 0.05), a higher wet weight-to-dry weight ratio (p < 0.05), and histologic findings of graft tissue injury than the control group. The difference in these parameters among the control, HT, and NC groups was not significant. Conclusions: Only pre-mortem hypoxia provoked by hypoventilation significantly impaired lung graft function in DCD lung transplantation. Ventilatory rather than circulatory deterioration can trigger the onset of warm ischemia.