Thermodiffusion for continuous quantification of hepatic microcirculation - Validation and potential in liver transplantation

Hepatic microcirculation is a main determinant of reperfusion injury and gr aft quality in liver transplantation. Methods available for the quantificat ion of hepatic microcirculation are indirect, are invasive, or preclude pos toperative application. The aim of this study was the validation of thermod iffusion in a new modification allowing long-term use in the clinical setti ng. In six pigs Doppler flowmeters were positioned around the hepatic arter y and portal vein for the measurement of total liver blood flow. Liver perf usion was quantified by thermodiffusion and compared to H-2 clearance as an established technique under baseline conditions, during different degrees of portal venous obstruction and during occlusion of the hepatic artery. Th ermodiffusion measurements were recorded for five days postoperatively foll owed by histological evaluation of the hepatic puncture site. Perfusion dat a obtained by thermodiffusion were significantly correlated to H-2 clearanc e (r = 0.94, P < 0.001) and to liver blood now (r = 0.9, P < 0.05). The agr eement between thermodiffusion and H-2 clearance was excellent (mean differ ence -2.1. ml/100 g/min; limits of agreement -12.5 and 8.3 ml/100 g/min). O cclusion of the portal vein or hepatic artery was immediately detected by t hermodiffusion, indicating a decrease of perfusion by 64 +/- 7% or 27 +/- 5 % of baseline, respectively, Perfusion values at baseline and during vascul ar occlusion were reproducible during the entire observation period. Histol ogical changes of the liver tissue adjacent to the thermodiffusion probes w ere minute and did nor influence long-term measurements. In vivo validation proved that enhanced thermodiffusion is a minimally invasive technique for the continuous, real-time quantification of hepatic microcirculation, Chan ges in liver perfusion can be safely detected over several days postoperati vely. The implication for liver transplantation has led to the clinical app lication of thermodiffusion. (C) 1999 Academic Press.