5
Views
0
CrossRef citations to date
0
Altmetric
Original Article

The Influence of Flow and Hematocrit on the Laser Doppler Flux Signal from the Surface of the Perfused Pig Liver

&
Pages 19-25 | Published online: 10 Jul 2009
 

Abstract

Objective: We tested the hypothesis that the measurement volume of the laser Doppler flowmeter (LDF) is too small to provide reliable quantitative estimates of total liver blood flow of large mammals, such as the pig.

Methods: In a perfused pig liver, the influence of changing (i) hepatic arterial (HA) and portal venous flows individually (n = 9), (ii) HA flow at fixed portal venous flow (50%, 70%, and 100% expected total liver blood flow), and (iii) hematocrit (0–30%) at fixed total liver blood flow on LDF flux was tested (n = 8).

Results: Linearity of LDF with hepatic arterial flow and portal venous flow was confirmed; however, the slope of the regression lines was higher for hepatic artery [1.92 ± 0.60 (SD)] than portal vein perfused livers (0.66 ± 0.34; P < 0.001). With portal venous flow at 50% and 70% total liver blood flow, changing hepatic arterial flow produced linear LDF versus flow responses, but at 100% total liver blood flow, linearity was achieved in only 6/9 livers. The coefficient of variation for the slopes of regression lines was always > 30%. At constant total liver blood flow (100 ml/min per 100 g), LDF response decreased linearly by a factor of about 2 on changing the hematocrit from 30% to 5% and markedly fell as the hematocrit was further decreased to zero.

Conclusions: These results suggest that (i) the LDF flux signal from the liver surface provides a poor measure of hepatic microcirculatory blood flow during changes in total liver blood flow as the LDF responds with about three times greater sensitivity to changes in hepatic arterial than in portal venous flow, and (ii) when hematocrit is falling, LDF may underestimate hepatic perfusion to a significant extent. In addition, due to high measurement variability, the LDF flux signal cannot be quantified in absolute perfusion units.

Reprints and Corporate Permissions

Please note: Selecting permissions does not provide access to the full text of the article, please see our help page How do I view content?

To request a reprint or corporate permissions for this article, please click on the relevant link below:

Academic Permissions

Please note: Selecting permissions does not provide access to the full text of the article, please see our help page How do I view content?

Obtain permissions instantly via Rightslink by clicking on the button below:

If you are unable to obtain permissions via Rightslink, please complete and submit this Permissions form. For more information, please visit our Permissions help page.