446: Successful Subzero Non-Freezing Preservation of Rat Lungs with Supercooling Technology

Purpose: Supercooling is defined as a non-freezing state of liquid below freezing temperature. Stable supercooling at the temperature between 0°C to –10°C is achieved in a newly developed refrigerator with a power voltage of 3,000 V. We hypothesized that supercooling would reduce metabolism of organ grafts and lungs preserved in supercooling would have better physiological function than in the clinically standard storage at 4°C. Methods and Materials: We investigated in a previously published isolated rat lung perfusion model, in which physiological parameters such as tidal volume, arterial oxygen tension, and lung weight were measured. The heart-lung block was preserved for 17 hr and subsequently reperfused for 60 minutes. All animals were divided into three groups. In the supercoolng group (n 7), non-freezing preservation at -2°C was kept in a supercooling refrigerator. In the control group (n 7), the ordinary hypothermic preservation was maintained at 4°C. In the sham group (n 7), after harvesting lungs were continuously perfused without hypothermic preservation. Results: Two animals in the control group were excluded from the following analysis because of severe lung edema within 12 minutes of reperfusion. Oxygen tensions at 60 minutes of reperfusion were 101.8 2.6 in the supercooling, 58.6 10.8 in the control, and 104.4 1.9 in the fresh (mmHg). At 60 minutes, tidal volumes were 2.0 0.1 in the supercooing, 1.0 0.3 in the control, and 2.2 0.1 in the fresh (mL). The lung weight gains during the 60 minutes were 1248 56, 2983 543, and 693 69, in supercooling, in control and in fresh, respectively (mg). Throughout the experiment, oxygen tensions and tidal volumes in the supercooling and the fresh were significantly higher than the control group(p 0.001, p 0.05, respectively), and the lung weight gains in the supercooling and the fresh were significantly lower than the control (p 0.001). Conclusions: Supercooling demonstrated the superiority in hypothermic preservation of rat lungs to the standard storage of 4°C in an isolated rat lung perfusion model.