Long-term preservation with interim evaluation of lungs from a non-heart-beating donor after a warm ischemic interval of 90 minutes

Abstract

Objective: To investigate the value of in situ preservation and ex vivo evaluation of lungs from a non-heart-beating donor (NHBD) prior to long-term cold storage.

Summary background data: The use of pulmonary grafts from NHBD might alleviate the organ shortage. However, viability testing of these grafts is mandatory to transplant only those lungs with excellent function.

Methods: Pigs were divided into two groups. In the control group, lungs were flushed, explanted, and stored for 4 hours (4 degrees C). In the study group, pigs were killed and left untouched for 90 minutes. Thereafter, the lungs were cooled for 150 minutes via chest drains. Graft function of the left lung in both groups was assessed in an isolated ventilation and reperfusion circuit 4 hours after death. The lung was then cooled and stored. Twenty-four hours after death, the pulmonary graft was reassessed in the same model.

Results: We did not observe a statistical significant difference between the two groups in pulmonary vascular resistance, mean airway pressure, and partial oxygen tension at each time point. There was also no statistical significant difference in wet-to-dry weight ratio. Finally, no statistical difference was found within both groups comparing the assessment at 24 hours with the interim evaluation at 4 hours.

Conclusions: These data demonstrate that: 1) 90 minutes of warm ischemia and 150 minutes of intrapleural cooling do not affect pulmonary graft function; and 2) NHBD lungs can be safely preserved up to 24 hours. Finally, we have demonstrated that interim ex vivo evaluation of NHBD lungs is a valid and safe method to assess graft function.

FIGURE 1. Schematic overview of different time periods in both experimental groups starting at death of the animals. HBD, heart-beating donor, NHBD, non-heart-beating donor. *Including time to prepare heart-lung block, warning up of the heart-lung block and 10 minutes assessment.

FIGURE 2. Isolated reperfusion circuit for ex vivo evaluation of pulmonary grafts. From the hard shell reservoir (a) the perfusate was recirculated by a centrifugal pump (b) passing a leukocyte filter (c) and an adult gas exchanger (d) before entering the pulmonary vasculature (e, heart-lung block). An inflow catheter was positioned in the pulmonary artery and an outflow catheter in the left atrium via the apex of the left ventricle. The lungs were ventilated via an endotracheal tube.

FIGURE 3. Decline in endobronchial temperature during lung preservation inside the cadaver in the NHBD group (n = 5).

FIGURE 4. Pulmonary vascular resistance in the two groups (n = 5 in each group). HBD versus NHBD at 4 hours, P = 0.83; HBD versus NHBD at 24 hours, P = 0.59; HBD versus NHBD within time, P = 0.62. Time effect irrespective groups, P = 0.07. Vertical bars represent 95% confidence intervals.

FIGURE 5. Mean airway pressure in the two groups (n = 5 in each group). HBD versus NHBD at 4 hours, P = 0.73; HBD versus NHBD at 24 hours, P = 0.52; HBD versus NHBD within time, P = 0.92. Time effect irrespective groups, P = 0.15. Vertical bars represent 95% confidence intervals.

FIGURE 6. Partial oxygen tension in the two groups (n = 5 in each group). HBD versus NHBD at 4 hours, P = 0.12; HBD versus NHBD at 24 hours, P = 0.92; HBD versus NHBD within time, P = 0.46. Time effect irrespective groups, P = 0.39. Vertical bars represent 95% confidence intervals.

FIGURE 7. Wet-to-dry weight ratio in the two groups after 24 hours (n = 5 in each group). HBD versus NHBD, P = 0.6.