Kathi Salley Randall, MSN, RNC, CNS, NNP-BC

INTRODUCTION

Over the last decade, amplitude-integrated EEG, aEEG has gained in popularity, but many Neonatologists state that they feel uncomfortable reading aEEG patterns and most say they have never received any training on aEEG (1,2).

As a brief review, aEEG is derived from the EEG signal collected from surface or needle electrodes placed over the central and parietal regions. The EEG signal is filtered, rectified, and compressed and then plotted every 15 seconds on a semi-logarithmic scale at a rate of 6 centimeters per hour. Normative voltage for the five most common aEEG patterns has been published for both term and preterm infants. (3,4)

There are currently three common ways that aEEG is utilized at the bedside:

• Assess background pattern to look for severity of brain injury
• Assess for the presence of sub-clinical seizures
• Assess for changes in background patterns over time that might indicate the effectiveness of medications and other neuroprotective interventions, like therapeutic hypothermia.

Although aEEG was historically used to select infants for some of the randomized control trials for hypothermia, this is no longer deemed necessary for determining eligibility for cooling in the era of clinical cooling for HIE. However, there may be a role for the use of aEEG to assess infants with “mild” encephalopathy who may benefit from cooling, or enrollment in future trials, who do not initially qualify for cooling based on the clinical exam score alone.

Since aEEG monitors have switched from paper to digital devices, there have been many enhancements that have increased their reliability but also their complexity. Due to its popularity, aEEG is now available as an optional display for most continuous videoEEG monitors. This integration allows for bedside care providers to assess the real-time brain function of infants in the NICU while still recording a comprehensive array of EEG. This dual set-up offers the advantage of easy bedside review of aEEG and full reporting and remote access by the neurodiagnostic and neurophysiology team.

Other monitors offer what is known as multi-modal monitoring which integrates several streams of monitoring data (i.e., aEEG, NIRS, HR, Sats, and BP) on to one screen for easier interpretation of changes in both neurologic and physiologic vital signs. These devices are especially useful for big data analysis for neonatal research projects as well as for clinical use.

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References:

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2. Boylan, GB. An international survey of EEG use in the neonatal intensive care unit. Acta Paediatr. 2010 Aug;99(8):11505. doi: 10.1111/j.1651-2227.2010.01809.x. Epub 2010 Mar 26.
3. Hellstrom -Westas, L., Rosen, I., de Vries, L. S., & Greisen, G. (2007). Amplitude-integrated EEG classification and interpretation in preterm and term infants. Neoreviews, 7(2), 76-86.
4. Hellström-Westas L, Vries LS, Rosén I. Atlas of AmplitudeIntegrated EEGs in the Newborn, 2nd ed. CRC PressI Llc; 2008.
5. ASET – The Neurodiagnostic Society – https://www.aset.org/f iles/public/Skin_Safety_During_EEG_Procedures.pdf
6. Thoresen M, Hellström-Westas L, Liu X and de Vries L (2010). Effect of Hypothermia on Amplitude-Integrated Electroencephalogram in Infants with Asphyxia. Pediatrics. 2010;126;e131 DOI: 10.1542/peds.2009-2938
7. Massaro AN et al. (2012). aEEG evolution during therapeutic hypothermia and prediction of NICUoutcome in encephalopathic neonates. Neonatology, 102 (3): 197-202.
8. Murray, D M et al. Arch Dis Child, Fetal Neonatal Ed. 2008; 93: F187-F191
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