Laser Doppler Flowmetry of Hepatic Microcirculation during Pringle’s Maneuver: Determination of Spatial and Temporal Liver Tissue Perfusion Heterogeneity

BACKGROUND: Laser Doppler flowmetry (LDF) is frequently used for non-invasive microvascular perfusion measurements. The aim of the present study was to analyze liver blood flow heterogeneity in detail using LDF devices under normal and low-flow conditions. MATERIALS AND METHODS: In 5 anesthetized and laparotomized Suabian-Hall strain pigs, systemic hemodynamics and hepatic arterial/portal venous blood flow were constantly recorded. Hepatic microcirculation was assessed by 2 different LDF devices, analyzing microvascular flow and velocity before, during and after inducing a Pringle's maneuver for hepatic inflow occlusion. Offline data analysis comprised differentiation between the two LDF devices used as well as calculation of temporal and spatial heterogeneity of liver perfusion. RESULTS: Pringle's maneuver induced complete inflow occlusion, confirmed by hepatic arterial/portal venous blood flow measurement. Laser Doppler signals showed a significant decrease during Pringle's maneuver. Spatial heterogeneity of flow and velocity increased more than temporal heterogeneity during Pringle's maneuver. CONCLUSION: Both LDF devices proved suitable for assessing hepatic microvascular perfusion during normal perfusion and low-flow conditions. Reduced microvascular perfusion induces a significant increase in temporal and spatial perfusion heterogeneity. In particular, the pronounced spatial heterogeneity requires measurements at different places when assessing hepatic microcirculation by LDF during impaired perfusion conditions.