Acronym for Anesthesia State and EEG Waves
BIS (Bispectral Index) is the acronym that represents both anesthesia state monitoring and processed EEG waveforms used during sedation and general anesthesia. 1
What BIS Represents
BIS monitoring is a noninvasive method that uses electroencephalographic (EEG) waveforms to assess a patient's level of consciousness during anesthesia. 2 The technology analyzes EEG signals through complex algorithms to generate a numerical index ranging from 0 to 100, where higher values indicate greater consciousness. 2
Clinical Correlation of BIS Values
The BIS scale provides specific numerical ranges that correspond to different anesthetic states:
- BIS 100: Fully awake 2
- BIS 70-90: Moderate sedation 2
- BIS 60-69: Deep sedation 2
- BIS 40-59: General anesthesia (target range for most surgical procedures) 2
- BIS <40: Deep hypnosis 2
- BIS 0: Complete EEG suppression 2
Guideline Recognition
Multiple major medical societies formally recognize BIS in their abbreviation lists:
- The American Academy of Pediatrics (AAP) defines BIS as "bispectral index" in their sedation monitoring guidelines 1
- The American Society of Anesthesiologists recommends processed EEG monitoring such as BIS for patients at higher risk of awareness 2
- BIS monitoring is specifically discussed as a processed EEG tool that examines EEG signals to correlate numerical values with depth of unconsciousness 1
Important Clinical Caveats
BIS has significant limitations that clinicians must understand:
- Agent-specific paradoxical responses: BIS values may paradoxically increase with ketamine and sevoflurane despite adequate anesthesia depth due to central excitation 1, 3
- Propofol correlation: BIS readings correspond most reliably with propofol sedation depth 1, 3
- Opioid insensitivity: Opioids have minimal and variable effects on BIS because it primarily measures hypnotic depth rather than analgesia 4, 3
- Neuromuscular blockade interference: BIS requires muscle activity in addition to awake EEG to generate accurate values, making it potentially unreliable in paralyzed but awake patients 5
- Time delay: BIS shows at least a one-minute delay in displaying changes in anesthetic state 6
Alternative EEG-Related Acronyms
While BIS is the most commonly referenced acronym combining anesthesia state and EEG, the guidelines also reference:
- EEG: Electroencephalogram/electroencephalography (the raw brain wave recording) 1
- AEP: Auditory evoked potentials 7, 8
- SSEP: Somatosensory evoked potentials 7
However, BIS specifically represents the processed, algorithm-derived index from EEG that correlates with anesthetic depth, making it the definitive acronym answering this question. 1, 2