Monitoring strategies in traumatic brain injury

Despite the increasing sophistication of monitoring equipment, the clinician must remember that monitoring of a head-injured patient begins with the neurologic examination, laboratory tests, and radiologic studies. Intracranial pressure monitoring via a ventriculostomy catheter remains the mainstay of neurosurgical critical care. Cerebral blood flow may be assessed by numerous techniques, including such noninvasive methods as transcranial Doppler. Reports have confirmed low cerebral blood flow immediately after injury, followed over the next several days by higher blood flows. Dynamic cerebral autoregulation may be assessed by noting the immediate cerebrovascular effects of either induced or spontaneous changes in cerebral perfusion pressure. This is most commonly done with transcranial Doppler or laser Doppler flowmetry. Regardless of the technique used to diagnose it, impaired autoregulation is consistently associated with poor outcome. Measurement of brain tissue oxygen tension is becoming increasingly popular in the intensive care unit and in the operating room. Determination of critical cerebral oxygen thresholds and correlation of brain tissue oxygen tension with other measures of cerebral metabolism are ongoing. Monitoring of brain temperature is also under investigation, especially in light of the growing interest in hypothermia as a treatment for severe head injury.