Application of laser Doppler flowmetry to measure cerebral microvascular perfusion in the fetal sheep.

Laser Doppler flowmetry (LDF) has been used to measure flow in various organs of the adult, but has not been applied to the mammalian fetus. The purpose of this study was to apply LDF to measure cerebral blood flow of the fetal sheep and to assess the possible errors and artifacts of the method caused by myometrial, fetal, and maternal movements. By three days after probe placement, the flow signal had decreased 55% from initial post surgical readings and thereafter it became stable. During fetal hypoxia, the signal increased 48% and during hypercarbia it increased 59%. After fetal death, the signal decreased to 48% of control level. After maternal death, it decreased to 9% and electrical zero could not be reached. LDF is useful to measure changes of fetal cerebral microvascular perfusion because it can provide continuous signals but care is required in data handling and probe fixation when used for the mammalian fetus.