Matthew J. Ritter, M.D.

Closed for Enrollment

• Effect of Timing of Commencement of Bispectral Index Monitoring in Relation to Muscle Relaxant Administration (BISII) Rochester, Minn.

  The primary objective of this study is to determine if the commencement of BIS monitoring relative to the administration of muscle relaxants has any effect on BIS values. The current study is a continuation of the project: “Bispectral Index: A Comparison of Bifrontal Montage Agreement” by Dr. Matthew Ritter and Wade Kreun, SRNA which validated the concurrent bifrontal use of BIS sensors. BIS monitors are FDA approved to assess the depth of sedation by analyzing segments of electroencephalogram (EEG) waves. They consist of a sensor, a digital signal converter, and a monitor. A BIS score is not a physiologic measurement, but a statistical predictor of the depth of anesthesia.1 The BIS monitor utilizes a proprietary algorithm to quantify changes in the EEG information during anesthesia and outputs a number (0-100) that corresponds with a patient’s level of consciousness. A level of 0 indicates no EEG activity (complete suppression of cortical activity); a level of 90 -100 indicates awake EEG activity.  Several studies demonstrated that BIS monitors may not be useful in paralyzed patients, as patients who were paralyzed and not sedated unexpectedly showed a large decrease in their BIS values following administration paralytic medications.2-4 Vivien et al2 found BIS values dropped an average of 24 points in already sedated patients when the patients were given paralytics. In the same year, Messner and colleagues paralyzed unsedated volunteers and found a dramatic drop in BIS values until paralysis wore off or was reversed.3 Schuller et al4 repeated the Messner experiment and found similar results with 18 of 20 unsedated volunteer’s BIS values dropping to levels expected of patients who were sedated. These results suggest that BIS monitors are integrating electromyography (EMG) data into its algorithm to derive a BIS value. Our hypothesis is that when the BIS monitor is activated after the patient is paralyzed, then EMG activity will not be applied to the BIS algorithm providing a cleaner data set and more accurate representation of a patient’s level of sedation and a more accurate indicator of actual BIS value.  Studying in this manner will require the subject to wear two BIS sensors in a frontal montage. The manufacturer of the sensors gives no guidance as to which side of the forehead an individual sensor is placed. However, the previous study by Dr. Matthew Ritter and Wade Kreun demonstrated BIS validity with the use of concurrent bifrontal sensors. The data obtained from that study is used as a framework for current BIS study.