Cerebrovascular Reactivity Assessed by Changes in ICP and Transcranial Doppler

Abstract

The ability to control ICP following traumatic head injury depends in part on cerebrovascular reactivity (CVR). By definition, cerebrovascular reactivity is defined as the change in blood flow (CBF) per torr change in PCO₂. With regard to ICP control, it is the concomitant reduction in blood volume achieved in response to hyperventilation which remains a potent therapeutic tool in the patient with raised intracranial pressure. However, with traumatic injury, vascular reactivity may be reduced thus compromising the volume compensatory response for ICP reduction as well as altering dynamics of cerebral blood flow. Thus, a quantitative measure of cerebrovascular reactivity is important to help determine the underlying mechanisms leading to metabolic crisis and pressure/volume instability following severe head injury.