The physiological basis for continuous electroencephalogram monitoring in the neonate

The overall aims in the care of the sick newborn are the preservation of brain function and optimal neurologic and developmental outcome. Paradoxically, online continuous functional monitoring in the neonate has traditionally focused on cardiorespiratory variables rather than cerebral function. Electrophysiological brain activity, as reflected by electroencephalogram (EEG), is well established as a tool for providing information about the current functional and metabolic state of the brain and the occurrence of epileptic seizure episodes. In neonatal care, EEG has been used extensively for estimation of the degree of cerebral maturation in preterm infants and for detection of abnormal patterns indicating focal and global cerebral lesions [1-3]. In the neonatal setting, as well as in intensive care in general, the EEG has been recorded intermittently, at best serially rather than continuously. Performing a full multichannel EEG in a newborn requires specialized technical skill in securing correct electrode positioning and impedances, as well as identification of extracerebral biologic and nonbiologic artifact sources. Interpretation of neonatal EEG is considered among clinical neurophysiologists a demanding task that must consider the specific EEG features related to different gestational age, activity state, and medication. The main disadvantage with intermittent conventional EEG during neonatal care is the difficulty in discriminating emerging trends of development of the electrocerebral activity over hours and days. If possible at all, it takes special skills not usually available in the neonatal intensive care unit (NICU) to identify long-term changes of EEG patterns. To have an impact on intensive care, monitoring of the electrocortical activity should have a continuous, simple recording setup and a small number of recording electrodes. Furthermore, EEG features that are immediately relevant for clinical decisions should be continuously available at the bedside and easily interpreted by the attending physician day and night. Such techniques have been applied for a long time in intensive care and anesthesia. It has also been used in neonatal monitoring, usually derived from a spectral analysis by fast Fourier transform (FFT) and presented as compressed spectral arrays (CSA) or spectral edge frequency (SE) [4].