Head Injury and Cerebral Circulatory Arrest

The evaluation of cerebral blood flow (CBF) following head injury is of great interest to clinicians and investigators. Various abnormalities in CBF have been studied in human head injury and in experimental animal models. Some of the abnormalities noted include impaired autoregulation, altered C02 reactivity, increased CBF (hyperemia), decreased CBF (oligemia), and vasospasm (1-4). It is believed that certain CBF abnormalities can lead to secondary damage to the brain in head-injured patients (5,6). Various methods to evaluate CBF following head injury available for clinical use include 133-xenon clearance using portable detectors, single-photon emission computed tomography (SPECT), and thermal dilution probes (710). Transcranial Doppler (TCD) can be used to monitor relative changes in CBF as well as to detect vasospasm following head injury (4, II). This emerging technology promises to be very valuable in the acute care setting . This chapter discusses some background information on physiological and hemodynamic changes that occur following head injury and how this information can be applied to clinical management. It also discusses the potential role of TCD in the evaluation and assessment of these hemodynamic changes.