6 secrets to reading your aEEG
In this blog, I'm going to focus on some of the basic skills around the "6 S's" of aEEG interpretation in the NICU.
I'll share how to interpret background aEEG as it relates to babies undergoing cooling for HIE (Hypoxic-Ischemic Encephalopathy).
When teaching how to use aEEG in the NICU, I often talk about the "6 S's" or six items that we should always look at when interpreting aEEG.
I believe that these principles apply really well to babies with HIE who are undergoing cooling, and I'll discuss each one of the 6 S's in more detail.
As a quick overview, the "6 S's" are:
Story: Consider the baby's gestational age, maternal history, delivery history, stage of encephalopathy, time since cooling started, and recent medications received. These may have a significant impact on the baby's background pattern.
Strength of the brain: Assess the background activity on the aEEG which represents the overall strength of the brain's electrical voltage. In the first day of cooling, it is not uncommon for the pattern to be discontinuous (with the lower margin below 5 microvolts) and the sooner the background returns to normal (above 5 microvolts) the more reassuring it is for a positive outcome.
Sleep-wake patterns: Evaluate the aEEG waveform for the presence or absence of sleep-wake patterns. For infants undergoing cooling, the presence of cycling is reassuring especially when they are visible before 48 hours of life; and particularly before rewarming.
Symmetry: If your aEEG displays more than one recording channel on the monitor screen, look for symmetry in the waveforms between the right and left sides of the brain. If asymmetries exist you may want to consider further investigations to identify any unilateral injuries.
Stability: Check for stability and especially improvement of the background pattern in the first 3 days of life. aEEG is an especially useful tool for predicting outcomes for infants with HIE.
Seizures: Monitor for seizures on aEEG and remember that as many as 80% of cooling babies may have seizures and most of them will be subclinical.
During cooling, aEEG can be a helpful tool. Previously, aEEG was used as a qualification to identify the sickest infants before we knew if cooling was safe and efficacious for babies with HIE. However, now that we know the benefits of cooling, aEEG is not necessary as a sole rule-out criterion. It can still be used during cooling to monitor the brain activity and guide treatment decisions.
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