Simultaneous Assessment of Vasoreactivity Using Transcranial Doppler Ultrasound and Cerebral Blood Flow in Healthy Subjects

Abstract

Summary: Blood flow velocities in both middle cerebral arteries and regional cerebral blood flow in their perfu sion territories were measured simultaneously in 36 healthy subjects. In 20 subjects, the measurements were first performed under basal conditions and then repeated 15-20 min after an intravenous injection of 1 g of acet azolamide. Reproducibility of simultaneous blood flow and velocity measurements was tested by examining 16 subjects on two occasions under basal conditions with an interval of 20 min. Relatively good reproducibility was found for repeated measurements of velocity and blood flow, being best when side-to-side asymmetry was as sessed. The increase in blood flow velocities after acet azolamide was symmetrical (right side, 34.2%; and left side, 35.5%), and the velocity increase was significantly correlated with basal values. The increase in cerebralThe effect of severe carotid occlusive disease on cerebral perfusion depends on the potential collat eral circulation and the ability of the cerebral arte rioles to dilate if there is a fall in perfusion pressure. When the capacity for compensatory vasodilation is overwhelmed and regional cerebral blood flow (rCBF) begins to fall, extraction of oxygen from the blood increases. This sequence of haemodynamic

Tissue Pulsatility Imaging of Cerebral Vasoreactivity During Hyperventilation

“…The most common method used to assess CVR though, is transcranial Doppler ultrasonography (TCD) (Dahl et al 1994;Markwalder et al 1984;Ringelstein et al 1988;Settakis et al 2003). TCD provides a low-cost, non-invasive means to measure blood flow velocities in the larger cerebral blood vessels in real-time.…”

Overnight Changes in the Cerebral Vascular Response to Isocapnic Hypoxia and Hypercapnia in Healthy Humans

“…The validity of this assumption depends on whether the MCA diameter remains constant in response to altered PCO 2 /PO 2 and/or blood pressure. This assumption has been challenged 22,23 ; however, the majority of research suggests that MCAV is a reliable index of CBF. 24 -27 Statistical Power Post hoc power calculations suggest that given the very small difference between the means and the standard deviation of the difference, the hypoxic study would need close to 10 000 patients to demonstrate a statistical significance of this magnitude of difference.…”

Pharmacotherapy of Glaucoma

“…45 In patients with low corneal endothelial cell count, corneal edema can occur. 45 Inhibition of carbonic anhydrase exerts potent vasodilator effects in the brain [60][61][62] and, as such, hemodynamic effects of topical dorzolamide and brinzolamide have been extensively studied. Brinzolamide as well as dorzolamide have also been found to increase ONH, choroidal and retinal blood flow in patients with glaucoma and experimental animals in several studies.…”