Background and Purpose-We sought to evaluate a new, angle-independent ultrasonic device for assessment of blood flow volume (BFV) in the internal carotid artery (ICA). Methods-Nineteen patients and 4 healthy volunteers were enrolled in a comparative study conducted in the Care Unit of the Division of Neurosurgery at UCLA Medical Center. All patients had been admitted because of severe brain injury: 15 patients with severe head trauma (Glasgow Coma Scale scoreՅ8) and 4 patients with subarachnoid hemorrhage due to aneurysm rupture. In all patients and subjects, cerebral blood flow (CBF) values obtained with the 133 xenon-clearance technique were compared with BFV measurements in the ipsilateral ICA. Results-Hemispheric CBF values showed a close and linear correlation with BFV measurements (rϭ0.76, PϽ0.0001).Global CBF values showed a higher correlation with the total BFV value obtained from both ICAs (rϭ0.84, PϽ0.0001). With 37 mL · min Ϫ1 · 100 g Ϫ1 as a cutoff value for the ischemic range, a BFV value of 220 mL/min would yield a positive predictive value of 91.7% and a negative predictive value of 82.6% (sensitivity 73.3%, specificity 95%). Conversely, BFV sensitivity and specificity were 60% and 96%, respectively, for the hyperemic range defined by a CBF value Ͼ55 mL · min Ϫ1 · 100 g Ϫ1 (positive predictive value of 85.7% and negative prediction value of 85.7%). Conclusions-BFV

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Background Significant alterations in autonomic nervous system (ANS) function, vasomotor reactivity, and cerebral blood flow may develop from damage to brain ANS regulatory areas in heart failure (HF). This preferentially right-sided injury occurs largely in autonomic structures perfused by the middle cerebral artery. Indications of altered, asymmetrical perfusion raise the potential for further neural damage. Objectives To determine whether the extent of middle cerebral artery blood flow velocity and vasomotor reactivity is altered on one side of the brain over the other in HF vs. control subjects, three ANS challenges were administered—each challenge recruited ANS regulatory areas potentially injured in HF. Methods Transcranial Doppler ultrasonography was used to measure cerebral blood flow velocity and vasomotor reactivity in 40 HF (mean age = 52.7 years, SD = 7.5; 27 males; left ventricular ejection fraction 26.8, SD = 8.3) and 42 control subjects (mean age = 48.3 years; SD = 6.0; 22 males) during 5% CO2 and hyperventilation, Valsalva, and orthostatic (upper body tilt) challenges. Results Lower cerebral blood flow velocity and abnormal vasomotor reactivity (p < .01) were noted in HF middle cerebral arteries during all challenges. More right-sided flow velocity reductions appeared in HF, with laterality differences noted during CO2 and orthostatic (p < .05), but not Valsalva challenges. Discussion Diminished cerebral blood flow velocity and altered vasomotor reactivity were associated with HF, changes being preferentially on the right-side; the asymmetry was more pronounced during CO2 and orthostatic challenges. The impaired blood flow regulation may contribute to the lateralized brain pathology in ANS areas, undermining autonomic control in HF.