Regional ischemia after head injury

Abstract

Purpose of review: To examine the evidence of regional cerebral ischemia after traumatic brain injury.

Recent findings: This review describes the mechanisms responsible for secondary brain injury and the similarities between traumatic and ischemic neuronal cell death. Cerebral ischemia is defined, and the difficulties of quantifying the burden of cerebral ischemia in the context of clinical head injury are presented. Recent clinical data obtained from monitoring brain tissue oxygenation, tissue metabolites using microdialysis, and cerebral blood flow, blood volume, oxygen metabolism, and oxygen extraction fraction using oxygen-15 positron emission tomography are discussed. These data highlight that significant episodes of regional ischemia occur within the acute phase after injury and are associated with poor outcome. Although various monitoring tools are capable of detecting significant episodes of regional ischemia, each of the currently available techniques is limited in its clinical application.

Summary: There is increasing evidence to suggest that a small but significant volume of brain tissue is at risk of ischemic injury after trauma. Future studies should examine the pathophysiology underlying such ischemia and how monitoring techniques can be used to direct appropriate therapy and influence outcome.