Assessment of cerebral blood flow by means of blood-flow-volume measurement in the internal carotid artery: Comparative study with a ¹³³xenon clearance technique

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 score≤8) and 4 patients with subarachnoid hemorrhage due to aneurysm rupture. In all patients and subjects, cerebral blood flow (CBF) values obtained with the ¹³³xenon-clearance technique were compared with BFV measurements in the ipsilateral ICA. Results - Hemispheric CBF values showed a close and linear correlation with BFV measurements (r=0.76, P<0.0001). Global CBF values showed a higher correlation with the total BFV value obtained from both ICAs (r=0.84, P<0.0001). With 37 mL · min^-1 · 100 g^-1 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 >55 mL · min^-1 · 100 g^-1 (positive predictive value of 85.7% and negative prediction value of 85.7%). Conclusions - BFV measurements with this new technology proved to accurately correlate with CBF values evaluated by the ¹³³xenon-clearance technique. These results support the implementation of this technique for bedside assessment of cerebral hemodynamics in critically ill neurosurgical patients.