Correlation between laser Doppler perfusion monitoring and hematocrit in hamster cheek pouch microcirculation.

The aim of this study was to investigate the relationships between laser Doppler perfusion monitoring (LDPM) measurements and different systemic hematocrits in microcirculation in terms of changes in oscillatory flow patterns. The hamster cheek pouch microvasculature was visualized by a fluorescent microscopy technique, and LDPM signals were derived from arterioles and venules under control conditions and after isovolemic hemodilution with saline and 6% dextran, MW 70,000 to 26.1 +/- 2.1%. Vasomotion, oscillations of microvascular blood flow (flow motion) and red blood cell (RBC) velocity were analyzed with Fourier transform and autoregressive modeling. LDPM recordings presented a significant increase in perfusion units (PU) during hemodilution-184 +/- 15 versus baseline 137 +/- 11 PU in arterioles and 40.2 +/- 3.5 versus 28.6 +/- 4.3 PU in venules-that was correlated with a significant increment in arteriolar and venular RBC velocity. There was a rise in the frequency [2.9 +/- 0.5 cycles per min (cpm) vs. 1.8 +/- 0.5 cpm] and spectral power of flow motion in arterioles whereas the increase in spectral power was related to a decrease in frequency (12.6 +/- 2.1 vs. 3.6 +/- 0.7 cpm) in venules. Oscillations in arteriolar and venular RBC velocity revealed coincident frequency components with flow motion patterns. The present data suggest that the LDPM measurements are more sensitive to velocity than hematocrit. Furthermore, hemodilution appears to affect differently arteriolar and venular flow motion patterns.