Monitoring for Impending Ischemia

The use of electrophysiological methods to monitor patients for cerebral ischemia is based on the observation that electrical brain activity is exquisitely dependent on adequate cerebral perfusion. The effect of ischemia on the EEG is dependent on the degree, duration, and rate of hypoperfusion, as well as on the cerebral metabolic rate, which itself can be influenced by sedation and body temperature. EEG can serve as an early indicator of ischemia, before clinical signs may be apparent and potentially before permanent injury occurs. Visual interpretation can be assisted by quantitative EEG analysis (QEEG). This chapter details the use of neuromonitoring for the detection of ischemia.