Bispectral Index (BIS) Monitoring via Continuous EEG
This test measures the Bispectral Index (BIS) during a continuous EEG (electroencephalogram) to assess your brain activity and sedation level, often used in anesthesia or critical care settings.
["The BIS helps doctors monitor how deeply you're sedated or asleep during procedures or in intensive care."]
Key facts at a glance
- LOINC
- 75918-3
- Short code
- BISEEG
- Synonyms
- Bispectral index Scre Ctx EEG
- Category
- chemistry
- Sample
- serum
- Container
- N/A - BIS monitoring uses proprietary forehead sensor electrodes connected to dedicated BIS monitor; no specimen container required
- Units
- N/A
- Ref low
- 40
- Ref high
- 60
- Critical range
- 20 N/A – 70 N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- Method
- Bispectral Index (BIS) analysis using processed electroencephalography (EEG) signals captured from forehead-mounted sensor array. BIS algorithm applies Fourier transformation and bispectral analysis to raw EEG waveforms to compute a dimensionless numerical value representing depth of anesthesia and level of consciousness. Real-time signal processing is performed by dedicated BIS monitoring device (e.g., Medtronic BIS Vista, Covidien BIS).
- SNOMED
- 129254005
- Specimen volume
- N/A - BIS is a real-time physiological monitoring parameter, not a laboratory test performed on a biological specimen. Continuous EEG signal acquisition via scalp electrodes.
- Stability
- N/A - BIS values are generated in real-time and displayed continuously on the bedside monitor. Data logging intervals typically range from 1-10 seconds depending on device settings. Historical data is stored on the monitoring device and can be exported.
- Hemolysis max
- 500
- Lipemia max
- 1000
- Icterus max
- 500
- TAT
- 4–24 hours
- Order
- routine
What Is the BIS Test Used For?
The BIS test is primarily used in medical settings like operating rooms or intensive care units to provide real-time feedback on your brain’s response to anesthesia or sedation. It helps healthcare providers adjust medications to maintain a safe and effective level of consciousness.
How Is the BIS Test Performed?
You’ll have small electrodes placed on your scalp to detect brainwave activity. The EEG records these waves, which are then processed by specialized equipment to generate the BIS score—a numerical value between 0 and 100 that reflects your brain’s activity level.
What Does the BIS Score Indicate?
A BIS score of 60–100 typically indicates light sedation or wakefulness, while scores below 60 suggest deeper sedation or unconsciousness. Scores near 0 may indicate a very deep anesthetic state. Your score is continuously monitored and adjusted by your healthcare team.
Is There Any Risk or Discomfort?
You may feel a slight tingling or itching where the electrodes are placed, but the procedure itself is painless. The electrodes stay in place for the duration of your procedure or stay in ICU, so you may need to stay still.
Reference range
BIS values range from 0 (isoelectric EEG, no cortical activity) to 100 (fully awake and alert). Recommended interpretation ranges: 100-85 = awake/light sedation; 85-65 = light to moderate anesthesia (recommended surgical range); 65-40 = deep anesthesia with increasing burst suppression; 40-0 = profound hypnotic state/burst suppression to isoelectric. Target range for general anesthesia: 40-60.N/A
No fasting required. Ensure forehead skin is clean, dry, and free of oils, makeup, or excessive hair for optimal electrode contact. Remove jewelry from head/face area. Verify BIS sensor placement per manufacturer specifications (typically at forehead and temple regions). Confirm sensor impedance is within acceptable range before initiating monitoring. Review patient medications including neuromuscular blockers and agents affecting EEG (propofol, sevoflurane, midazolam, ketamine, dexmedetomidine).
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
The BIS test is critical for ensuring precise sedation during surgeries or procedures, reducing risks like oversedation or wakefulness. It helps prevent complications such as postoperative confusion, breathing difficulties, or unintended movements. In ICU, it supports safe sedation management for patients who are mechanically ventilated or critically ill.
Short name
BIS EEG Monitoring
Frequently asked questions
Why was I asked to have this test?
How long does the test take?
Will I feel anything during the test?
Sources
- 1
- 2Lab Tests OnlineSource
- 3
Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.
This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.
This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.
If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.
Medically reviewed by WellAlly Editorial Team Last reviewed August 16, 2026. · Read our editorial policy