Amplitude-integrated Electroencephalography: A New Approach to Enhancing Neurologic Nursing Care in the Neonatal Intensive Care Unit*

A New Approach to Enhancing Neurologic Nursing Care in the Neonatal Intensive Care Unit

Shuyuann Wang Foreman, PhD, RN; Lauren Thorngate, PhD(c), RN, CCRN


NAINR. 2011;11(3):134-140. 

In This Article

Making Sense of aEEG Tracing Characteristics and Interpretation

Although interpretation of cEEG requires years of practice and intensive training to appreciate the subtleties of artifact, physiologic variability, and complex waveform recognition, aEEG is presented to clinicians as a simplified screening tool with reliance on visual patterns of a trended display. Amplitude-integrated electroencephalography signal appears as a dark band with sinusoidal periods of widening and narrowing (Fig 1). Generally, aEEG tracing is visually interpreted by pattern recognition based on five basic variables: continuity (density of traces, discontinuous indicates wide trace with increased variability), presence of cycling (rhythmic periodic widening and narrowing of the trace), amplitude (in microvolts) of the lower (minimum) and upper (maximum) border of the band, and bandwidth (the difference between the lower and upper margins of the trace's narrowest part).[17,27,49] Normal aEEG tracings in preterm infants have been established in several studies.[14,17,24,27–29,31,49]

Figure 1.

Amplitude-integrated EEG tracing of a healthy preterm infant displayed on the CFM screen. It shows aEEG background signal (in microvolts) on the upper screen and impedance (in kilo-ohms) on the lower screen. The letters marked events that occurred at real time during the recording. This aEEG tracing shows no interruptions during the recording and stable, low impedance (10 kΩ), indicating high-quality recording (reprinted with permission from Biol Res Nurs 2011;13:3).

A commonly used description of background EEG is continuity of signal, which when trended shows a tight, narrow pattern alternating between low and higher amplitudes. The presence of periodic cycling between continuity (depicting active organized brain function) and discontinuity (recognized by lower amplitude, less organized signal within the background continuity) is an indicator of healthy function. In mature, term infants, the cycling may represent changes in sleep-wake states between awake periods and active sleep as compared with deeper, quiet sleep. During sleep, the brain waves change from a lower amplitude or power of signal, to a higher amplitude, less dense pattern as the sleep stage deepens. In preterm or ill infants, the background may reflect primarily a discontinuous pattern, either because of immaturity or injury. Minor changes in lower border amplitude trending toward cycles may signify improvements in brain function among infants recovering from hypoxic or other brain injury. Serial recording of aEEG over a period of days or weeks is useful to assess recovery of continuity and emergence of cycling.[36,39,50]

Amplitude-integrated EEG background patterns vary and develop with increasing age. Studies of preterm infants and evolving aEEG patterns are described by gestational age (GA), postnatal age (PNA), and the combination of GA plus PNA called postmenstrual age. Maturational changes in aEEG background patterns of healthy preterm infants are well described: discontinuous activity decreases, continuous activity increases with increasing GA,[14,28,49] PNA,[28] and postmenstrual age.[27,31] With increasing GA, investigators document lower number of high amplitude bursts and early presence of cyclic background activity.[14,49] Discontinuous background patterns are normal in preterm infants but not present in healthy full-term infants,[14] reflecting the immaturity of preterm infants' brain. Seizure patterns can be identified on the aEEG traces as repetitive, spiky, transient rise of the lower and upper margins.[12] Several studies have shown that aEEG is sensitive in predicting neurologic outcomes of preterm and full-term infants. Abnormal aEEG background patterns were associated with adverse neurologic outcomes.[14,26,33,51]


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