HICU - Background Activity.pdf

17 Background Activity Kevin F. Haas IN THIS CHAPTER Standardized terminology for description of EEG background in critically ill patients The spectrum of EEG background activity Key components of EEG bac...

17 Background Activity Kevin F. Haas IN THIS CHAPTER Standardized terminology for description of EEG background in critically ill patients The spectrum of EEG background activity Key components of EEG background assessment KEY POINTS EEG interpretation in critically ill patients is most helpful when standardized terminology is used with consistent reporting of frequency, amplitude, reac- tivity, and sleep-state transitions. Assessment of EEG background activity in critically ill patients with altered mental status provides important complementary information to the clinical exam. EEG reactivity provides important prognostic information and should be assessed during the EEG recording of all encephalopathic patients. This chapter utilizes definitions based on American Clinical Neurophysiology Society (ACNS) standardized critical care EEG terminology (1). I. BACKGROUND A. Why is monitoring EEG background activity important? While often nonspecific for etiology, EEG background activity provides a real-time window for monitoring change in global cerebral function. In certain situations, EEG background activity provides important prognostic infor- mation. B. Terminology for describing EEG background activity in ICU EEG monitoring Symmetry 152 Copyright Springer Publishing Company. All Rights Reserved. From: Handbook of ICU EEG Monitoring, Second Edition DOI: 10.1891/9780826168627.0017  Chapter 17 Background Activity 153 EEG background should be compared in left and right hemispheres and identi- fied as either symmetric, mildly asymmetric (asymmetry in amplitude on refer- ential recording of 1 Hz frequency). Breach effect Noted for presence or absence Posterior dominant rhythm Specified as present or absent Document frequency to the nearest 0.5 Hz and presence of reactivity to eye opening and closure Predominant background frequency Delta, theta, or alpha. If two or three frequency bands are present, record each one. Variability Record as yes/no or unclear on the basis of the presence or absence of transi- tions in background frequency and amplitude. Reactivity Records change in cerebral EEG activity to stimulation. This may include changes in amplitude or frequency including attenuation of activity. The strength and/or nature of the stimulus should be noted. Appearance of muscle activity or eye blink artifacts does not qualify as reactive. Amplitude (voltage) Record as normal, low (most or all activity