Skip to Main Content

++

Currently available in the United States:

++

  • Bispectral Index (BIS™, Covidien)
  • SEDLine™ Patient State Index (PSI™, Masimo)
  • M-Entropy™ (GE Healthcare)
  • SNAP II™ (Stryker)

++

Also available in other countries:

++

  • Cerebral State Index (CSI™, Danmeter)
  • Narcotrend™ (Drager)
  • NeuroSENSE™ (Carefusion)

++

All monitors work on the principle that EEG changes caused by GABA agonists are, in general:

++

  • Predictable
  • Observable
  • Reproducible

++
Table Graphic Jump Location
Favorite Table | Download (.pdf) | Print
Anesthetics and EEG
Agents that correlate with processed EEG valuesAgents that do not correlate with processed EEG values
  • Halogenated volatile gases
  • Propofol
  • Benzodiazepines
  • Barbiturates
  • Ketamine
  • Nitrous oxide
  • Etomidate
  • Opioids
++

Processed EEG monitors, through differing algorithms, generate an index value (0–100) that reflects the state of frontal EEG activity and quasi-linearizes the relationship between dose of GABA agonist and index value.

++

EEG changes seen with GABA agonists include changes in:

++

  • Predominant frequencies
  • Relative power distribution
  • Phase relationship and randomness
  • Pattern changes, such as burst suppression

++
Table Graphic Jump Location
Favorite Table | Download (.pdf) | Print
EEG Waveform as a Function of Anesthetic Depth
Wave nameAssociated frequencies (Hz)Usual anesthetic state when prominent
γ (gamma) or β230–80Conscious
β (beta)12–30Conscious or initial excitation with induction
Image not available. (alpha)8–12Conscious with eyes closed and relaxed or general anesthesia (with spindles)
θ (theta)4–8General anesthesia
δ (delta)0–4Deep anesthesia
++
Table Graphic Jump Location
Favorite Table | Download (.pdf) | Print
Pros and Cons of Using Processed EEG Monitors
AdvantagesDisadvantages
  • On average, less use of volatile agents or propofol
  • On average, faster emergence
  • On average, less time before eligible for PACU discharge
  • Potential to better identify unexpected outliers: those that require either more or less agent than average
  • Possible decrease in recall of unintended consciousness during surgery, particularly in the high-risk patient (but perhaps not better than utilizing end-tidal gas monitoring with alarms enabled)
  • Allow real-time display of one to four channels of raw frontal EEG
  • Cost
  • Ideal use involves watching and interpreting raw EEG wave: most anesthesiologists do not have appropriate basic knowledge
  • No absolute value assures unconsciousness or consciousness
  • Values not real time: some processing time and smoothing functions cause a delay between change in state and change in index
  • In some patients, there appears to be a more quantal relationship between agent level and EEG than a linear one. In these patients with a “plateau,” titrating agent levels down may result in a sudden state change with patient movement
++
Table Graphic Jump Location
Favorite Table | Download (.pdf) | Print
Various EEG Monitors
MonitorRecommended range for GANotes
BIS™40–60β ratio (related to activity in 30–47 Hz range) is component of upper range of index. Facial muscle EMG activity will increase this value and when EMG activity is present, BIS may be higher than expected. In this condition, BIS will decrease ...

Want remote access to your institution's subscription?

Sign in to your MyAccess profile while you are actively authenticated on this site via your institution (you will be able to verify this by looking at the top right corner of the screen - if you see your institution's name, you are authenticated). Once logged in to your MyAccess profile, you will be able to access your institution's subscription for 90 days from any location. You must be logged in while authenticated at least once every 90 days to maintain this remote access.

Ok

About MyAccess

If your institution subscribes to this resource, and you don't have a MyAccess profile, please contact your library's reference desk for information on how to gain access to this resource from off-campus.

Subscription Options

AccessAnesthesiology Full Site: One-Year Subscription

Connect to the full suite of AccessAnesthesiology content and resources including procedural videos, interactive self-assessment, real-life cases, 20+ textbooks, and more

$995 USD
Buy Now

Pay Per View: Timed Access to all of AccessAnesthesiology

24 Hour Subscription $34.95

Buy Now

48 Hour Subscription $54.95

Buy Now

Pop-up div Successfully Displayed

This div only appears when the trigger link is hovered over. Otherwise it is hidden from view.