Transcranial Doppler and Near Infrared Spectroscopy can evaluate the hemodynamic effect of carotid artery occlusion
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Abstract
BACKGROUND AND PURPOSE: Cerebral hemodynamic and metabolic changes can compensate
for the decrease in cerebral blood flow occurring in patients with carotid
occlusive disease. At present, a complete assessment of the cerebral adaptive
status is only possible with positron-emission tomography. Near-infrared
spectroscopy (NIRS) is a noninvasive technique that, providing a real time
assessment of fluctuations in cerebral hemoglobin, has been used to estimate the
cerebral blood volume and to measure cerebral vasomotor reactivity (VMR).
Moreover, NIRS technology, by allowing the absolute measurement of absorption and
scattering coefficients of brain, can determine the oxyhemoglobin and
deoxyhemoglobin concentrations in situ in the blood stream.
METHODS: In order to evaluate different aspects of the cerebral hemodynamic
status, 27 subjects with symptomatic and asymptomatic carotid artery occlusion
and 30 healthy subjects underwent a simultaneous examination by means of
transcranial Doppler (TCD), able to reliably detect collateral circulation and
VMR, and NIRS at rest condition and during CO2 reactivity test.
RESULTS: The main finding of this study was the demonstration of a difference
between asymptomatic and symptomatic patients in terms of mean flow velocity
increase (52.4% versus 21.0%; P<0.001) estimated by TCD and of hemoglobin
saturation increase measured by NIRS (6.8% versus 3.8%; P=0.015).
CONCLUSIONS: The opportunity to perform NIRS and TCD simultaneously provides
useful information about both hemodynamic and metabolic cerebral adaptive status
in patients with occlusive disease in a simple, noninvasive, and reliable way