American Clinical Neurophysiology Society Standardized EEG Terminology and Categorization for the Description of Continuous EEG Monitoring in Neonates: Report of the American Clinical Neurophysiology Society Critical Care Monitoring Committee

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BACKGROUNDCritically ill neonates are at high risk for adverse neurologic sequelae, but the bedside evaluation of a neonate's neurologic status, especially cortical functioning, is extremely limited. In such circumstances, continuous video EEG provides particularly useful information about brain function and can identify electroencephalographic seizures without clinical correlate (Clancy et al., 1988; Murray et al., 2008). For these reasons, continuous video EEG monitoring is a useful tool in the intensive care nursery. The American Clinical Neurophysiology Society has recently produced guidelines regarding methods and indications for continuous EEG monitoring in neonates (Shellhaas et al., 2011).A challenge in EEG monitoring of neonates is to understand the clinical significance of various EEG patterns. In the adult population in intensive care unit, there has been extensive debate, for example, regarding the importance of fluctuating rhythmic patterns (Hirsch et al., 2004; Oddo et al., 2009; Orta et al., 2009; Vespa et al., 1999). The American Clinical Neurophysiology Society Critical Care Monitoring Committee has generated standardized terminology of rhythmic EEG patterns in the critically ill to facilitate multicenter collaborations to determine whether these patterns have clinical significance (Hirsch et al., 2005). Neonates have distinctive EEG patterns that necessitate separate terminology.This document is the consensus of experts to establish standardized neonatal EEG nomenclature aimed at improving consistency and facilitating collaborative research. Where evidence exists to support a particular definition, it is noted. For terms with historically variable definitions, alternative nomenclature is referenced but a single definition is proposed. We anticipate that future revisions will incorporate feedback and emerging research building on this initial effort. Many of the studies on which these criteria are based used routine-length EEG recordings, and in this limited context, values such as acceptable duration of interburst intervals have been offered. However, greater variability may be expected in recordings of longer duration. It is hoped that this document provides groundwork for collaboration to determine the clinical significance of various EEG patterns in continuous monitoring of the critically ill neonate.DETAILS TO BE REPORTEDCharacterization of a 24-hour period of continuous video EEG recording should include the following (Table 1).Documentation of the patient’s postmenstrual age (PMA = gestational age, measured from the time of the last menstrual period + chronological age) at the time of recording (Engle, 2004) (We use the term PMA in accordance with the American Academy of Pediatrics policy statement on age terminology in the perinatal period. However, we recognize that historically, many seminal investigations of EEG ontogeny calculated gestational age from the time of conception rather than the last menstrual period. This has been traditionally termed conceptional age (CA). The LMP occurs approximately 2 weeks before conception.).a) Term = 37 up to 44 weeks of PMAb) Preterm = less than 37 weeks of PMAc) Post term = 44 to 48 weeks of PMADocumentation of neuroactive medications at the time of recording. This includes sedatives, hypnotics, anxiolytics, general anesthesia, and antiepileptic drugs. An ideal report would also document when these medications are administered during the recording.Documentation of the depth and duration of hypothermia during the recording, and whether it is spontaneous or induced.An ideal report would also document the clinical changes that have the potential to impact cerebral function. These would include sudden hemodynamic instability, rapid changes in respiratory function, or cardiorespiratory failure.Documentation of the number of hours of recording that cannot be interpreted as a result of technical problems.Detailed characterization of the background EEG features during the first hour of recording.

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