Long-term measurement of liver microcirculation in dogs and humans

We verified the possibility of using laser Doppler fluxmetry for prolonged monitoring of hepatic perfusion; we confirm the ability of an implantable laser Doppler microprobe to be in constant 'optical contact' with the liver and thus to transmit a stable microcirculatory signal for a prolonged period of time, and we correlate the response of liver microcirculation to the hepatic artery blood flow reduction in order to estimate this flow by continuous monitoring of microcirculation.

Hepatic microcirculation was recorded by a single-fiber microprobe implanted in the livers of 8 dogs and of 5 surgical ICU patients. In another 7 dogs, liver microcirculation as well as hepatic artery blood flow were recorded digitally, while an occluder was used to decrease hepatic artery flow.

Analysis of the initial data of microcirculation revealed a nonsignificant variation between consecutive time segments, a finding confirming the hypothesis that laser Doppler gives a very stable signal over a long period of time. Polynomial regression analysis, performed on data pairs obtained from microcirculation and hepatic artery blood flow revealed a regression coefficient y = -54.22 + 1.07x + 0.0046x2 (y = hepatic artery blood flow, x = liver microcirculation).

This finding means that it is possible to watch the hepatic artery flow values continuously by the use of this equation and simple monitoring of liver microcirculation. Thus, the use of laser Doppler fluxmetry with implantable microprobes seems promising as a novel method for continuous assessment of hepatic artery blood flow.