Abstract
Doppler ultrasound has been widely used to investigate the mechanisms of cerebral ischaemia in sick newborns. If the diameter of the vessel is constant, then changes in cerebral blood flow velocity (CBFV) reflect true changes in volume flow. Even if vessel diameter increases by distention under increased pressure, it is widely assumed that the changes in CBFV will be in the same direction as true changes in flow.
4 newborn piglets underwent simultaneous measurements of cerebral blood flow by electromagnetic flowmetry (EM) on the common carotid artery (extracerebral branches were ligated) and Doppler CBFV. The two methods agreed well under normal conditions ie within moderate CO2 and blood pressure changes. Pathological changes were induced by inlusion of 6 - 11 ml/kg of a) blood which had been infected, b) blood which was incompatible (human) c) blood which was chilled to 4 °C d) blood heated to 45 - 50 °C.
Incompatible blood resulted in a 75% increase in EM CBF but only 10% increase in Doppler CBFV. Cooled blood gave Doppler changes that were greater than the EM changes and heated blood gave Doppler changes that were smaller than the EM changes. Infected blood resulted in a decrease in Doppler CBFV of 50% while the EM CBF increased by 30%.
These findings could be explained by vasoactive substances changing the diameters of large arteries. It is therefore possible that Doppler CBFV measurements in critically ill infants with eg sepsis might be misleading.
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Thoresen, M., Haaland, K. & Whitelaw, A. CEREBRAL DOPPLER CAN SERIOUSLY MISREPRESENT FLOW CHANGES. Pediatr Res 35, 279 (1994). https://doi.org/10.1203/00006450-199402000-00151
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DOI: https://doi.org/10.1203/00006450-199402000-00151