Carotid Doppler hemodynamics in posttraumatic intracranial hypertension.

Repeated Doppler sonograms were performed on the common carotid arteries of patients with severe brain injury. The evolution of the flow-wave shape in 9 patients who developed massive intracranial hypertension and finally died with cerebral circulatory arrest demonstrated that, with increasing peripheral vascular resistance, the diastolic flow diminished while the peak systolic flow was not significantly affected. Thus, the so-called pulsatility index, a measure of the pulsatile characteristic of the sonogram, can be used as a semiquantitative measure of intracranial perfusion. Measurements on healthy control subjects provided pulsatility indexes between 1.5 and 2.0. In cases of posttraumatic brain edema, these values increased gradually. These data suggest that values higher than 3 are associated with severe intracranial hypertension and the decerebrate state. In angiographically demonstrated cerebral circulatory arrest, the pulsatility index was found to range between 6 and 8.