The purpose of this study is to learn more about an Entropy monitor that the
anesthesiologist will be using.
Depth of anesthesia monitors are increasingly used in clinical anesthesia practice.
Bispectral Index (BIS) and M-Entropy are examples to these devices, both of which are
available at our institution. Both BIS and M-Entropy use a unilateral, single channel of EEG
to derive a number indicating the anesthetic depth. These devices have similar disposable
skin probes that can be applied on either side of the forehead. Since the depth of
anesthesia for an individual is the same over the whole brain cortex at a given point in
time, BIS numbers obtained over the left and right side of the forehead should agree. The
same should be true for M-Entropy as well.
A recent study, however, showed that two separate BIS probes, applied over the left and
right forehead of the same patient at the same time, can give significantly different
numbers. This has not been studied for M-Entropy. BIS and M-Entropy use different
mathematical algorithms that process the raw EEG signal to compute a numeric value.
Therefore, it is possible that M-Entropy may show different results in a similar study
The aim is to investigate the same-patient reproducibility of M-Entropy by monitoring and
recording Entropy variables over both the left and the right side of the forehead of
patients under general anesthesia.
- Patients scheduled to have surgery under general anesthesia, with a minimum of 60
minutes expected duration.
- Non-English speaker
- Patients younger than 18 years of age
Mehemet Ozcan, MD
The University of Oklahoma Health Sciences Center, Department of Anesthesiology