Abstract
Previous studies using the xenon-133 cerebral blood flow (CBF) method have documented the impairment of CO2vasoresponsivity after a severe head injury, but only global values can be obtained reliably with this technique. We studied CO2vasoresponsivity using the stable xenon-enhanced computed tomographic CBF method, which provided information about well-defined cortical regions and deep brain structures not available with the xenon-133 method. In 17 patients with admission Glasgow Coma Scale scores of 8 or less, hemispheric CO2vasoresponsivity ranged from 1.3 to 8.5% per mm Hg change in partial CO2pressure. Lobar, cerebellar, basal ganglia, and brain stem CO2vasoresponsivity frequently varied from the mean global value by more than 25%. In all but one patient, local CO2vasoresponsivity in one or more of these areas differed from the mean global value by more than 50%. The greatest variability occurred in patients with acute subdural hematomas and diffuse (bihemispheric) injuries. This variability in CO2vasoresponsivity has important implications for the effective and safe management of intracranial hypertension that frequently accompanies severe head injury.

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