Week 8 BIS Flashcards
What is BIS?
BIS (Bispectral Index) is an EEG-based monitor to assess depth of anesthesia.
What numerical range does BIS convert EEG signals into?
BIS converts EEG signals into a numerical value from 0 to 100, where 100 = Awake and <40 = Deep anesthesia.
What is the purpose of BIS?
The purpose of BIS is to prevent intraoperative awareness and optimize anesthetic depth.
What is PSI?
PSI (Patient Safety Index) is similar to BIS but uses a different target range.
Why is monitoring anesthetic depth important?
Monitoring anesthetic depth prevents intraoperative awareness, allows precise titration of anesthetic agents, promotes faster emergence, reduces drug consumption, and enhances postoperative recovery and safety.
What are alternative devices for monitoring depth besides BIS?
Alternative EEG monitors like SedLine and PSI exist, relying on similar processed EEG principles but using different algorithms.
How does BIS analyze EEG signals?
BIS analyzes EEG signals using proprietary algorithms that factor in spectrogram, bispectrum, and burst suppression levels.
What is the output range of BIS?
BIS outputs a number from 0 (isoelectric EEG) to 100 (awake).
What does a BIS score of 100 indicate?
A BIS score of 100 indicates the patient is fully awake.
What does a BIS score of <40 indicate?
A BIS score of <40 indicates deep hypnosis.
What is the electrode placement for BIS?
Electrode placement for BIS is on the forehead and temple.
What are the advantages of BIS monitoring?
Advantages of BIS monitoring include near real-time anesthetic depth feedback, reduced anesthetic consumption, improved recovery speed, and potential reduction in postoperative cognitive dysfunction.
What is a limitation of BIS monitoring?
Limitations include a delay of 20–30 seconds between EEG signal and display, and it can be expensive at $10–15 per disposable sensor set.
How does ketamine affect BIS readings?
Ketamine increases high frequency activity, leading to falsely high BIS readings and is associated with increased epileptiform activity.
What effect does nitrous oxide have on BIS?
Nitrous oxide increases high frequency and decreases low frequency, resulting in false readings.
How does dexmedetomidine affect BIS?
Dexmedetomidine produces EEG similar to natural sleep, which may appear falsely low; patients may still respond to verbal commands while BIS readings correlate with unconsciousness.
What is the BIS score interpretation for 65–85?
A BIS score of 65–85 indicates the patient is sedated.
What is the significance of a BIS score <40 for more than 5 minutes?
A BIS score <40 for more than 5 minutes is associated with increased postoperative mortality.
What does ‘triple low’ refer to?
‘Triple low’ refers to low BIS, low MAP, and low MAC, which is associated with increased mortality and length of stay (LOS).
What did the BAG-RECALL trial find regarding BIS?
The BAG-RECALL trial found that BIS did not prevent awareness better than end-tidal agent monitoring.
What is the conclusion regarding the use of BIS?
BIS is best used as a trend, not in isolation, and should be interpreted with other data such as vital signs, end-tidal anesthetic concentration (ETAC), and clinical judgment.
The nurse anesthetist is aware that the following patients are not ideal to use the BIS
monitor on as readings may not be reliable or fully accurate: (select all that apply)
A) Infants and children < 18 years old
B) Patients receiving Ketamine as the induction agent
C) Patients > 60 years old
D) Patients receiving Fospropofol as the induction agent
E) Patients receiving Nitrous Oxide with other inhalation agents
• Correct Answer: A) Infants and children < 18 years old, B) Patients receiving Ketamine
as induction agent, C) Patients >60 years old, E) Patients receiving Nitrous Oxide with
other inhalation agents
• Rationale: Patients receiving Ketamine as an induction agent or Nitrous Oxide with
other inhalation agents will have altered waveforms from what is expected. The BIS
monitor can interpret the waveforms to an incorrect value that is not true to the patient’s
depth of anesthesia. Additionally, patients <18 and >60 years old have age-related EEG
waveform differences that can skew the BIS monitor’s readings. (Gropper et
What is the primary purpose of BIS monitoring?
A) To measure cerebral oxygen levels
B) To assess the depth of anesthesia using EEG signals
C) To correlate with heart rate during surgery
D) To monitor anesthesia concentration
• Correct Answer: B) To assess the depth of anesthesia using EEG signals
• Rationale: BIS monitoring provides near real-time data on patient consciousness levels,
helping anesthesia providers decrease risk for intraoperative awareness
What BIS range is recommended for general anesthesia?
A) 80-100
B) 65-80
C) 40-65
D) 20-40
Correct Answer: C) 40-65
• Rationale: A BIS value between 40 and 65 is considered an appropriate depth for general
anesthesia, reducing the risk of awareness. (Butterworth, 2022)
