Characterization of the Bispectral Index in Healthy Volunteers Receiving Inhalation Anesthetics in Combination With Opioids in a Randomized Trial.

Summary

This randomized volunteer study evaluated BIS values and responsiveness across sevoflurane, desflurane, and isoflurane regimens, with selected opioid combinations. BIS50 values ranged from 67.5 to 76.2 and BIS95 values from 49.1 to 63.3; BIS alone had an area under the receiver operating characteristic curve of at least 0.95 for predicting responsiveness. Opioids added to sevoflurane had minimal influence, whereas desflurane produced somewhat lower BIS thresholds.

Key Findings

• BIS50 ranged from 67.5 to 76.2 across anesthetic regimens, while BIS95 ranged from 49.1 to 63.3.
• BIS predicted responsiveness strongly, with area under the receiver operating characteristic curve values of at least 0.95.
• Adding remifentanil or fentanyl to sevoflurane had minimal impact on BIS50 and BIS95, while desflurane was associated with slightly lower values.

Clinical Implications

BIS can provide useful information about responsiveness during volatile anesthesia, but clinicians should interpret thresholds in the context of the specific anesthetic agent and clinical setting. The findings do not justify applying these values directly to patients under surgical stimulation or to older or medically complex populations.

Limitations

• The analyzed sample was 143 participants rather than the 211 randomized volunteers.
• Participants were young, healthy volunteers without sustained noxious surgical stimulation.
• Findings may not generalize to patients with comorbidities, older adults, or clinical anesthesia with surgery.

Future Directions

Clinical studies should validate agent-specific BIS thresholds during surgery, in older and critically ill patients, and under combinations of opioids, neuromuscular blockers, and other anesthetic agents. Research should also examine whether individualized BIS interpretation improves outcomes rather than merely predicting responsiveness.