Heterogeneous Flow Patterns During Hypothermic Machine Perfusion Preservation of Livers1

Background. Hypothermic machine perfusion preservation (MPP) has the potential to relieve the current donor shortage problem by providing superior preserved tissue and viable non-heart-beating donor tissue. For the liver, MPP has not improved preservation. Currently, the major cause of damage associated with MPP of livers is unknown. Methods. An intravital microscopy study was conducted to investigate the state of sinusoidal perfusion during MPP and the effect of a high potassium perfusion solution on liver microcirculation. Results. The results showed that there was an increase in vascular resistance (>200%) when the liver was perfused with a high K solution at either 37° or 5°C and with a flow rate of 14 or 5 ml/min. Heterogeneous flow perfusion at the microcirculatory level was evident with regions of no-flow, which after a 10 hr MPP protocol remained unperfused during rewarming. These areas also displayed increased cellular injury as determined by propidium iodide staining (245.4 vs. 12.3 cells) compared with regions that were perfused during MPP. Conclusion. These results suggest that a heterogeneous flow pattern occurs during MPP of the liver as a result of the high K perfusion solution. Regions of no-flow during extended MPP remained unperfused during rewarming resulting in tissue damage and may represent a cause of liver damage associated with MPP.