EFFECT OF HEMODILUTION ON CEREBRAL BLOOD FLOW : CONTINUOUS MEASUREMENT OF MICROCIRCULATORY REGIONAL CEREBRAL BLOOD FLOW BY LASER-DOPPLER FLOWMETRY

The object of this investigation is to study the effects of isovolemic hemodilution on regional cerebral blood flow (rCBF) in non-ischemic rats. Regional CBF was measured by Laser-Doppler flowmetery and hydrogen clearance method in the rat's thalamus simultaneously. It is possible for the Laser-Doppler flowmeter (LDF) to make continuous measurement of rCBF. Thirteen Wistar rats were anesthetized with 1.5% halothane by mask. Isovolemic hemodilution was performed to exchange of 7 ml of human albumin for 7 ml rat blood gradually. After this process the values of hematocrit (Hct) decreased from 44.8 to 31.7. The rCBF of the thalamus measured by LDF increased by 25.8%. The increase in rCBF correlated almost linearly with the decrease in Hct. The decrease of mean red cell density caused by hemodilution in the tissue is a decrease factor of CBF which is the theoretical basis of this method. In spite of the decrease factor measured CBF was increased. These data suggest that the remarkable increase in red cells velocity may occur with hemodilution