Temperature Dynamics of Porcine and Human Lungs During Static Ice Storage: Ice Is Not 4 °C

Background: Static ice storage (SIS) has long been accepted as the conventional lung preservation method, assuming to maintain 4 °C temperature. Although never directly confirmed by temperature measurements, this assumption has been widely accepted. We aimed to measure lung and preservation temperature with SIS in porcine experiments and clinical observations. Methods: Porcine lungs were preserved with SIS for 8 h (group I, n = 3) and 3 h followed by 10 °C storage (group II, n = 3). Tissue (tissueT°), first bag preservation solution (psT°) and second bag saline (salineT°) temperature were monitored. In clinical lungs (n = 4), psT° was monitored during SIS. Surface (surfaceT°) and core (coreT°) temperature were assessed before and after SIS (n = 62). Results: After 4 h in porcine lung group I, average tissueT° was 0.66 °C, psT° was 0.12 °C and salineT° was -0.02 °C. After 3 h in group II, average tissueT° was 1.90 °C, psT° was 0.57 °C and salineT° was 2.33 °C. In clinical observations, psT° was below 4 °C after 9-13 min and 0 °C after 78-267 min. After SIS, median surfaceT° was 1.25 °C (min-max; -3.2-9.2 °C) and coreT° was 1.45 °C (-0.4-4.8 °C). Conclusions: SIS leads to rapid temperature drops below 4 °C, approaching 0 °C within 2-4 h. The post-SIS lung temperature shows considerable variability and does not consistently remain at the commonly assumed 4 °C, posing potential freezing injury to donor lungs.