Changes in the Bispectral Index in Response to Experimental Noxious Stimuli in Adults under General Anesthesia

Abstract

Objective. Pain assessment is a major challenge in nonverbal patients in the intensive care unit (ICU). Recent studies suggest a relationship between the Bispectral Index (BIS) and nociceptive stimuli. This study was designed to examine changes in BIS in response to experimental noxious stimuli. Methods. Thirty participants under general anesthesia were in this quasiexperimental, within subject, pre- and poststudy. In the operating room (OR), BIS was monitored during moderate and severe noxious stimuli, induced by a thermal probe on the participants' forearm, after induction of general anesthesia, prior to surgery. Results. Significant increases in BIS occurred during moderate (increase from 35.00 to 40.00, P = 0.003) and severe noxious stimuli (increase from 37.67 to 40.00, P = 0.007). ROC showed a sensitivity (Se) of 40.0% and a specificity (Sp) of 73.3% at a BIS value > 45, in distinguishing a moderate from a severe noxious stimuli. Conclusion. BIS increased in response to moderate and severe noxious stimuli. The Se and Sp of the BIS did not support the use of the BIS for distinction of different pain intensities in the context of deep sedation in the OR. However, the results justify further studies in more lightly sedated patients such as those in the ICU.

Assessing pain objectively: the use of physiological markers

“…Entropy processes raw cortical EEG and frontal EMG signals to produce two indices based on their frequency range, called ‘response entropy’ and ‘state entropy’. Although studies have shown that nociceptive stimulation increased BIS, response entropy and state entropy, this was heavily dependent on both the baseline BIS levels and the degree of concurrent hypnosis. It did not correlate with the quality or intensity of noxious stimuli , despite steady‐state, end‐tidal sevoflurane concentrations.…”

Changes in the Bispectral Index in Response to Loss of Consciousness and No Somatic Movement to Nociceptive Stimuli in Elderly Patients

“…[ 1 2 3 ] But it was still controversial whether BIS could be used in the assessment of the level of pain and adequacy of analgesia. [ 4 5 6 7 8 9 ] Some researchers think that BIS primarily measures the degree of sedation and sleep and does not reliably reflect the autonomic response to pain. In addition, BIS changes during nociceptive stimulation can be affected by many other variables such as sedatives, anesthetics, opioids (which decrease BIS by reducing cortical activity),[ 10 ] and neuromuscular blocking agents (which decrease BIS by reducing electromyogram [EMG] activity).…”

Machines, mathematics, and modules: the potential to provide real-time metrics for pain under anesthesia

“…These indices are used to guide intraoperative anesthetic titration – from patient full wakefulness to light anesthesia but to a large extent do not convey enough information on the noxious stimulations during surgical procedures. For example, when noxious stimuli are applied, the BIS index can increase in some patients, decrease in some other patients, or stay unchanged 56 . Instead of relying on post-processed indices, several studies have recommended looking at raw electroencephalograms to identify changes in EEG band powers following noxious stimulations 57 .…”

“…For example, when noxious stimuli are applied, the BIS index can increase in some patients, decrease in some other patients, or stay unchanged. 56 Instead of relying on post-processed indices, several studies have recommended looking at raw electroencephalograms to identify changes in EEG band powers following noxious stimulations. 57 Patterns that are more frequently seen include an increase in EEG beta power (“beta arousal”), an increase in EEG delta power (“delta arousal”), and a reduction in EEG alpha power (“alpha dropout”).…”