CAROTID ARTERIAL BLOOD-FLOW IN THE OVINE FETUS AS A CONTINUOUS MEASURE OF CEREBRAL BLOOD-FLOW

OBJECTIVE: The purpose of this study was to establish a continuous mea sure of cerebral blood flow in the ovine fetus with a transit time flo w probe. METHODS: Seven chronically catheterized fetal sheep were stud ied near term with placement of a 3R Transonic flow probe on the exter nal carotid artery, just proximal to the internal maxillary artery. Bl ood flow changes were induced by altering maternal inspired oxygen and carbon dioxide concentrations, with cerebral and extracerebral blood flows also determined by the microsphere technique. RESULTS: Although absolute carotid and cerebral blood flow values were only modestly rel ated under the present study conditions (r = 0.60, P < .05), both the percent change and the actual change in carotid arterial blood flow sh owed a strong linear correlation with that for cerebral blood flow (r = 0.84, P < .01, and r = 0.72, P < .02) but less so with that for extr acerebral blood flow (r = 0.44 and r = 0.28). CONCLUSION: Measurements of carotid blood flow as studied with a transit time flow probe and i nduced blood gas changes can provide for a continuous assessment of ch anges in blood flow to tile ovine fetal brain.