EEG/SEDLine Monitoring Tips

1) Swab the forehead twice with alcohol swabs to clean the skin prior to electrode placement.

2) Place the EEG and obtain a waveform prior to induction.

3) Monitor Setup:

a. The default monitor set up should display all of the parameters described below

b. EEG alarms: SEDLine alarm range is set to low/high limits of 25/50 for PSi (Patient State Index by

default.

c. Ensure that relevant parameters are being displayed: The PSi (Patient State Index), ARTF (Artifact),

SR (Suppression Ratio), EMG (Electromyographic Strength), SEF (Spectral Edge Frequency 95%) and

DSA (Density Spectral Array).

* EEG waveform reflects changes in patients’ hypnotic state much more rapidly that processed EEG parameters*

4) EEG waveform nomenclature and frequency ranges:

▪ Delta: 1 - 4 or 0 - 4 Hz; Slow delta: <1 Hz

▪ Theta: 4 - 8 Hz

▪ Alpha: 8 - 12 Hz (Mu)

▪ Beta: 12 - 30 Hz (or 14 - 30 Hz); Low beta:

<20 Hz; High beta: 20 - 30 Hz

▪ Gamma: >30 Hz (to 100s Hz)

▪ Sigma: 12 - 14 Hz; frequency band for sleep

spindles during physiological sleep

Spectral Edge

Frequency

(SEF) for the

left and right

sides

5) Spectral Edge Frequency (SEF) interpretation:

▪ SEF = frequency below which 95% of the total power of the patient's EEG is located

▪ SEF ≤12Hz is consistent with general anesthesia and low likelihood of awareness

6) Density Spectral Array (DSA) interpretation:

7) EEG of the awake patient: Dominated by high frequency (i.e., high beta and gamma) activity, usually of low

amplitude, producing a fuzzy-appearing wave on the faster 25-50 mm/s tracing. High-frequency, high-amplitude

activity (EMG) and periodic high-amplitude deviations (from blinking) may be observed.

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8) EEG during general anesthesia: A pattern of slow delta waves (<1 Hz) coupled with alpha spindles (8-12 Hz) is

often desired. There should be an absence of high beta (20-30 Hz) waves and absence of any periods of burst

suppression.

▪ Waves in the alpha (8-12 Hz), theta (4-8 Hz) or low beta (12-20 Hz) frequency ranges, often termed

spindles, may not be prominent in older patients with cognitive impairment

▪ Zoomed in EEG waveform demonstrating slow waves in the delta range (~1 Hz) and spindle pattern

consistent with general anesthesia, the dotted white trace demonstrates waves in the slow delta range:

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Very slow high amplitude delta waves

Persistent alpha (~10Hz) spindle pattern

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9) EEG suppression: Any flattened interval on the EEG tracing (EEG suppression) indicates excessive anesthetic

depth or suggests the presence of other suppressive stimuli (e.g., cerebral ischemia).

10) Do not throw away the cables, only the patient sticker is disposable. If this is a THRIVE study patient, please

page the study coordinator at: 30227 to pick up the SEDLine monitor.

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EEG Suppression