Intracranial Doppler flow velocimetry compared with extracranial carotid blood flow measurements

The effects of changes in carotid blood flow on intracranial blood flow velocities were examined in six newborn lambs under general anesthesia. Carotid blood flow was measured using electromagnetic flow cuffs. A combined continuous and pulsed Doppler instrument was used to measure intracranial blood flow velocities on the base of the skull through artificially created fontanels. Baseline carotid blood flow was 96 +/- 18 ml X min-1 (mean +/- SD) and increased by 58 +/- 13% following contralateral occlusion. A close correlation between changes in carotid blood flow and intracranial blood flow velocity was found (y = -6.28 + 3.72x, Sy = 182.3, Sy/x = 0.30, r = 0.89, p less than 0.001). The closest estimate of changes in blood flow to the brain was the temporal mean of the cross-sectional average velocity.