Which monitoring modality can help prevent intraoperative awareness by assessing depth of anesthesia?

• A. End-tidal CO2
• B. Bispectral index (BIS) monitoring
• C. Invasive arterial pressure monitoring
• D. Central venous pressure

Answer: (B)

Monitoring depth of anesthesia to prevent intraoperative awareness relies on measuring brain activity rather than just vital signs. Bispectral index monitoring analyzes EEG signals to produce a numerical value that reflects the hypnotic level of anesthesia. A typical target range around 40–60 helps ensure the patient remains adequately unconscious, reducing the risk of awareness and recall during surgery. End-tidal CO2 shows ventilation and CO2 elimination but does not provide information about the brain’s level of consciousness. Invasive arterial pressure and central venous pressure track hemodynamics, not the depth of anesthesia. Keep in mind that BIS values can be affected by artifacts or certain drugs, so use it alongside clinical judgment and other monitors.