The effects of graded experimental trauma on cerebral blood flow and responsiveness to CO2

Abstract

The effects of graded mechanical cerebral trauma on cerebrovascular reactivity of CO2 were studied in 26 cats. A fluid-wave percussion model was employed which delivered an epidural trauma of fixed duration and variable amplitude. The animals were maintained at arterial normoxia, with constant monitoring of intracranial and systemic arterial pressures, EEG, and end-tidal CO2. Following trauma, cerebral blood flow was measured using the ion clearance technique at PaCO2 [CO2 partial pressure] levels ranging sequentially from 20-60 mm Hg. Cerebrovascular reactivity for control animals (uninjured) was 2.7%. In the group with mild trauma (0.76-1.90 atm) reactivity was impaired (1.7%), and it was abolished in the severely injured group (2.90-4.60 atm). Mild injuries did not alter resting blood flows, while severe trauma resulted in a significant decrease in cerebrovascular resistance. Intracranial and systemic arterial pressures were altered proportionately to the level of cerebral injury. Trauma to the brain-stem vasoregulatory centers may account for these findings.