BIS in Critically Ill Patients in ICU

May 6, 2026 updated by: Mahidol University

The Comparison of Bispectral Index Parameter Between Critically Ill Patients With and Without Decreased Mental Status and Its Association With Clinical Outcomes

The Bispectral Index (BIS) is a monitor that converts brain electrical activity from EEG into a simple number from 0 to 100. A higher number means the patient is more awake, while a lower number means deeper sedation or reduced brain activity.

In general, 100 means fully awake, 80 suggests light to moderate sedation, 60 is commonly used as a target for general anesthesia with a low chance of awareness, 40 indicates deep anesthesia, 20 suggests marked brain suppression with burst suppression on EEG, and 0 indicates no detectable cortical electrical activity.

Although BIS was originally developed for use in the operating room, it has also been applied in the ICU to help guide sedation, avoid over- or under-sedation, and assess consciousness in patients who cannot be evaluated reliably using standard clinical scores. BIS has also been studied as a possible tool for predicting outcomes in comatose ICU patients, such as those after cardiac arrest, stroke, encephalitis, or traumatic brain injury. However, evidence is still limited for its use in predicting outcomes among ICU patients with any form of decreased consciousness. Therefore, this study was conducted to explore that role.

Study Overview

Status

Not yet recruiting

Conditions

Intervention / Treatment

Detailed Description

The Bispectral Index is the output of a multi-stage process that transforms the brain's electrical activity into a simplified metric. This process begins with non-invasive data acquisition and proceeds through advanced computational analysis to derive the final index.

The BIS monitor translates the EEG data into a number on a scale from 0 to 100. This index is designed to provide a direct measure of a patient's level of consciousness and response to sedation, with specific numeric ranges corresponding to general clinical states.

The generally accepted clinical correlations for the BIS scale are as follows:

  • 100: This value indicates a patient who is fully awake and alert, corresponding to a state of responsiveness to a normal voice.
  • 80: This range is typically associated with light to moderate sedation or anxiolysis. A patient in this range may respond to loud verbal commands or mild physical stimulation, such as prodding or shaking.
  • 60: This value is a critical threshold often targeted for general anesthesia. It represents a low probability of explicit recall and unresponsiveness to verbal stimuli. A BIS value of less than 60 has a high sensitivity for identifying a state of drug-induced unconsciousness, making it a key target in the operating room to prevent awareness.
  • 40: This range signifies a deep hypnotic state, with a greater degree of cortical suppression than is typically required for general anesthesia.
  • 20: A BIS value in this range indicates the presence of burst suppression on the EEG. This pattern, characterized by periods of electrical activity (bursts) alternating with periods of isoelectricity (suppression), reflects a very deep level of brain suppression seen with high doses of anesthetic agents or in conditions like barbiturate coma or severe anoxic brain injury.
  • 0: A BIS value of 0 represents a flatline or isoelectric EEG, indicating the absence of detectable cortical electrical activity.

BIS monitoring was adapted from the operating room to the ICU to help manage the difficult task of sedating critically ill patients.

Its main goals in the ICU are to:

  • Prevent the risks of over- or under-sedation.
  • Provide an objective number to guide medication dosage.
  • Assess consciousness in patients who can't be evaluated by normal methods. BIS monitoring is being used more frequently to assess the depth of sedation in ICU patients, as opposed to relying solely on clinical scoring systems.

The Bispectral Index (BIS) has been used to predict clinical outcomes in ICU patients with coma from various causes, including post-cardiac arrest, cerebrovascular disease, viral encephalitis, and traumatic brain injury. However, there is limited research on using BIS to predict outcomes for patients with any decreased level of consciousness in the ICU. Therefore, this study was initiated.

Study Type

Interventional

Enrollment (Estimated)

40

Phase

  • Not Applicable

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Contact

Study Locations

  • Thailand
    • Bangkok
      • Bangkok Noi, Bangkok, Thailand, 10700
        • Department of Anesthesiology, Faculty of Medicine Siriraj Hospital, Mahidol University
        • Contact:
        • Principal Investigator:
          • Annop Piriyapatsom, M.D.
        • Sub-Investigator:
          • Chatchawan Uacharuporn, M.D.
        • Sub-Investigator:
          • Tanuwong Viarasilpa, M.D.
        • Sub-Investigator:
          • Nattachai Hemtanon, M.D.
        • Sub-Investigator:
          • Suchanun Lao-amornphunkul, M.D.
        • Sub-Investigator:
          • Natthicha Papbamnarn, M.D.
        • Sub-Investigator:
          • Chayanan Thanakiattiwibun

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Ages Eligible for Study

  • Adult
  • Older Adult

Accepts Healthy Volunteers

No

Description

Inclusion Criteria:

  1. Age≥18years
  2. RASS score ≤ -3 as case
  3. RASS score 0 to -1 as control
  4. Expected ICU length of stays ≥ 24hours

Exclusion Criteria:

  1. Contraindication for BIS monitoring (wound or infection at forehead)
  2. No space for attach BIS monitoring at forehead
  3. Patient with sedative drugs (Propofol, Midazolam, Dexmedetomidine)
  4. Patient with acute stroke
  5. Patient was already on EEG monitoring
  6. Denied by patients or patient's surrogates

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

  • Primary Purpose: Other
  • Allocation: Non-Randomized
  • Interventional Model: Parallel Assignment
  • Masking: None (Open Label)

Arms and Interventions

Participant Group / Arm
Intervention / Treatment
Active Comparator: Decreased mental status
Other: Processed EEG monitoring
Monitor processed EEG using BIS
Placebo Comparator: Normal mental status
Other: Processed EEG monitoring
Monitor processed EEG using BIS

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Measure Description
Time Frame
BIS value
Time Frame: 24 hours following inclusion
Average BIS value during 24 hours period of monitoring
24 hours following inclusion

Secondary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Length of stay in SICU
Time Frame: Up to 90 days following inclusion
Total days of stay in SICU
Up to 90 days following inclusion
Length of stay in hospital
Time Frame: Up to 90 days following inclusion
Total days of stay in hospital
Up to 90 days following inclusion
SICU discharge status
Time Frame: Up to 90 days following inclusion
Status whether alive or decease
Up to 90 days following inclusion
Hospital discharge status
Time Frame: Up to 90 days following inclusion
Status whether alive or decease
Up to 90 days following inclusion
Status at 30 days
Time Frame: Up to 30 days following inclusion
Status whether alive or decease
Up to 30 days following inclusion
Status at 90 days
Time Frame: Up to 90 days following inclusion
Status whether alive or decease
Up to 90 days following inclusion
ICU Memory
Time Frame: Up to 90 days following inclusion

ICU Memory Tool:

Three domains: ICU environment (family, alarms, tubes), feelings (pain, agitation, confusion), delusions (dreams, hallucinations).

A self-rated format for frequency, ranging from 0 to 2 (never, sometimes, and often).
Up to 90 days following inclusion
Post-traumatic Stress Disorder
Time Frame: Up to 90 days following inclusion
Post-traumatic Stress Disorder (PTSD) assessed by Impact of Event scale (IES)-6 which comprised 6 questions, each scored from 0 to 4 (Not at all, a little bit, moderately, quite a bit, extremely). Mean IES-6 score ≥ 1.75 considers positive screening for PTSD.
Up to 90 days following inclusion

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

Mahidol University

Publications and helpful links

The person responsible for entering information about the study voluntarily provides these publications. These may be about anything related to the study.

General Publications

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Estimated)

May 15, 2026

Primary Completion (Estimated)

January 31, 2027

Study Completion (Estimated)

March 31, 2027

Study Registration Dates

First Submitted

May 3, 2026

First Submitted That Met QC Criteria

May 6, 2026

First Posted (Actual)

May 13, 2026

Study Record Updates

Last Update Posted (Actual)

May 13, 2026

Last Update Submitted That Met QC Criteria

May 6, 2026

Last Verified

May 1, 2026

More Information

Terms related to this study

Keywords

Other Study ID Numbers

  • 037/2569(IRB1)

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

YES

IPD Plan Description

The datasets used and/or analyzed during the current study are available from the corresponding author on reasonable request.

IPD Sharing Time Frame

IPD and supporting information will be available once the study has already published and last for 1 year.

IPD Sharing Access Criteria

The datasets used and/or analyzed during the current study are available from the corresponding author on reasonable request.

IPD Sharing Supporting Information Type

  • STUDY_PROTOCOL
  • SAP
  • CSR

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

No

Studies a U.S. FDA-regulated device product

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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