Continuous EEG and evoked potential monitoring in the neuroscience intensive care unit

Abstract

As with other methods long used in intensive care units (ICU) and operating rooms (OR), the goal of neuroscience ICU continuous EEG (NICU-CEEG) and evoked potential (NICU-EP) monitoring is to extend our powers of observation to detect abnormalities at a reversible stage. EEG is an appropriate monitoring tool because it is linked to cerebral metabolism, is sensitive to ischemia and hypoxemia, correlates with cerebral topography, detects neuronal dysfunction at a reversible stage, and is the best method for detecting seizure activity. When applied systematically, it can impact medical decision-making in 81% of monitored patients. It is useful in monitoring precarious cerebral perfusion at the bedside, and it has revealed that nonconvulsive seizures, undetectable otherwise, occur in 34% of NICU patients. In convulsive status epilepticus, NICU-CEEG can help avoid undertreatment and overtreatment. In comatose patients, it can provide useful prognostic information as well as detect potentially treatable causes. Traditional impediments to its application are yielding to technological advances and educational efforts. Real-time digitized EEG in particular has been a major advance. Within limits, somatosensory evoked potential monitoring (ICU-SEP) is useful in the prognosis of coma, but it is less helpful in monitoring focal cerebral ischemia. Brainstem auditory evoked potential monitoring has a relatively restricted role in the NICU but is helpful in distinguishing structural from nonstructural causes of coma and can supplement ICU-SEP in predicting outcome.