Effect of Hypothermia on BIS and PSI Correlation During Cardiopulmonary Bypass

Effect of Hypothermia on the Correlation Between Bispectral Index (BIS) and Patient State Index (PSI) During Cardiopulmonary Bypass

The goal of this observational study is to evaluate whether hypothermia affects the relationship between electroencephalography-derived indices during cardiac surgery in adult patients undergoing cardiopulmonary bypass.

The main questions it aims to answer are:

Does the correlation between Bispectral Index (BIS) and Patient State Index (PSI) change between normothermic and hypothermic phases during cardiopulmonary bypass? How do BIS and PSI values change in response to decreasing body temperature?

Participants will:

Undergo standard general anesthesia for elective on-pump coronary artery bypass surgery Be monitored simultaneously with BIS and PSI devices during surgery Have data recorded at predefined temperature-based time points during cardiopulmonary bypass

Study Overview

• Status: Recruiting
• Conditions: Cardiopulmonary Bypass; Hypothermia; Anesthesia; Depth of Anesthesia Monitoring
• Intervention / Treatment: Other: Simultaneous BIS and PSI Monitoring

Detailed Description

Hypothermia during cardiopulmonary bypass (CPB) is known to influence cerebral metabolism and electroencephalographic activity. Processed electroencephalography-derived indices such as the Bispectral Index (BIS) and Patient State Index (PSI) are commonly used to monitor anesthetic depth; however, these indices are generated using different proprietary algorithms. While previous studies have demonstrated moderate to high correlation between BIS and PSI under normothermic conditions, it remains unclear whether this relationship is preserved during hypothermic CPB.

This prospective observational study aims to evaluate the effect of hypothermia on the relationship between BIS and PSI in adult patients undergoing elective on-pump coronary artery bypass grafting. Both indices will be monitored simultaneously throughout the intraoperative period using standard sensor placement.

Data will be collected at predefined time points representing normothermic, hypothermic, and rewarming phases of CPB. The primary analysis will focus on comparing the correlation between BIS and PSI at a normothermic reference point (36°C) and a hypothermic reference point (32°C).

To minimize confounding effects, anesthetic management and physiological parameters will be maintained within routine clinical target ranges, and relevant variables will be recorded throughout the procedure. Secondary analyses will explore temperature-dependent changes in each index and agreement between clinically relevant depth-of-anesthesia categories.

This study is designed to clarify whether hypothermia alters the relationship between commonly used processed EEG indices, which may have implications for intraoperative neuromonitoring and anesthetic management during cardiac surgery.

• Study Type: Observational
• Enrollment (Estimated): 60

Contacts and Locations

• Study Contact: Name: AHMET R DOĞAN, M.D; Phone Number: +905427988070; Email: a.ridvandogan@gmail.com

Study Locations

• Turkey (Türkiye)
  • Serdivan
    • Sakarya, Serdivan, Turkey (Türkiye)
      • Recruiting
      • Sakarya University Training and Research Hospital, Department of Anesthesiology and Reanimation
      • Contact: AHMET R DOĞAN; Phone Number: +905427988070; Email: a.ridvandogan@gmail.com
      • Sub-Investigator: Ahmet R Dogan

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult; Older Adult
• Accepts Healthy Volunteers: No

• Sampling Method: Non-Probability Sample

Study Population

Adult patients undergoing elective on-pump coronary artery bypass grafting (CABG) with cardiopulmonary bypass at a single tertiary care center will be included. All participants will receive standard general anesthesia and perioperative management according to institutional protocols. Patients will be monitored intraoperatively with both Bispectral Index (BIS) and Patient State Index (PSI) devices, and data will be collected at predefined time points during normothermic, hypothermic, and rewarming phases of cardiopulmonary bypass.

Description

Inclusion Criteria:

• Age ≥18 years
• Elective on-pump Coronary Artery Bypass Grafting (CABG) surgery
• Planned use of general anesthesia
• Written informed consent

Exclusion Criteria:

• Preexisting neurological disease
• Use of medications affecting Electroencephalography (e.g., antiepileptics)
• Severe hepatic dysfunction
• Emergency surgery
• Inadequate signal quality for anesthesia depth monitoring

Study Plan

How is the study designed?

Number of groups / cohorts

1

Cohorts and Interventions

Group / Cohort

Intervention / Treatment

Elective On-Pump CABG Patients Undergoing CPB; Adult patients undergoing elective on-pump coronary artery bypass grafting with cardiopulmonary bypass will be included. All participants will receive standard general anesthesia and intraoperative management according to institutional protocols. Bispectral Index (BIS) and Patient State Index (PSI) will be monitored simultaneously throughout surgery. Data will be collected at predefined time points across normothermic, hypothermic, and rewarming phases of cardiopulmonary bypass to evaluate the relationship between these indices under varying temperature conditions.

Other: Simultaneous BIS and PSI Monitoring; This observational study does not involve any experimental intervention. All participants will receive standard anesthesia and surgical care according to institutional protocols. The study focuses on simultaneous intraoperative monitoring using Bispectral Index (BIS) and Patient State Index (PSI) devices. Sensors for both monitors will be applied prior to induction of anesthesia, and values will be recorded at predefined time points during normothermic, hypothermic, and rewarming phases of cardiopulmonary bypass. No changes will be made to routine clinical management, and all treatments will be determined by the attending anesthesiologist.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Difference in Correlation Between Bispectral Index (BIS) and Patient State Index (PSI) Under Normothermic and Hypothermic Conditions	The primary outcome is the difference in Pearson correlation coefficients between BIS and PSI measured at predefined normothermic (36°C) and hypothermic (32°C) phases during cardiopulmonary bypass. Correlation coefficients will be calculated separately for each phase and compared using Fisher z-transformation to determine whether hypothermia alters the relationship between these indices.	Intraoperative (during cardiopulmonary bypass at predefined time points)

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Change in Bispectral Index (BIS) and Patient State Index (PSI) per Degree Celsius During Cooling and Rewarming	This outcome evaluates temperature-dependent changes in BIS and PSI during cooling and rewarming phases of cardiopulmonary bypass. The rate of change in each index per degree Celsius (Δindex/°C) will be calculated using repeated measurements across predefined temperature points. Linear mixed-effects models will be used to estimate the relationship between core temperature and index values while accounting for within-subject variability.	Intraoperative (during cooling and rewarming phases of cardiopulmonary bypass)
Effect of CPB Initiation on the Relationship Between Bispectral Index (BIS) and Patient State Index (PSI)	This outcome assesses the impact of cardiopulmonary bypass initiation on the relationship between BIS and PSI. Pearson correlation coefficients will be calculated at the pre-CPB stable normothermic time point (T4) and after CPB initiation under normothermic conditions (T5). The change in correlation between these two time points will be evaluated to determine whether initiation of CPB alters the association between the indices.	Intraoperative (comparison of pre-CPB and post-CPB initiation time points)
Agreement in Clinical Depth Categories Between Bispectral Index (BIS) and Patient State Index (PSI)	This outcome evaluates the agreement between BIS and PSI when classified into clinically relevant depth-of-anesthesia categories. BIS values will be categorized as >60 (light), 40-60 (adequate), and <40 (deep), while PSI values will be categorized as >50 (light), 25-50 (adequate), and <25 (deep). Agreement between the two indices will be assessed using Cohen's kappa coefficient. Comparisons will be performed separately for normothermic and hypothermic phases to determine whether temperature affects categorical agreement.	Intraoperative (during predefined normothermic and hypothermic phases of cardiopulmonary bypass)

Collaborators and Investigators

• Sponsor: Sakarya University
• Investigators: Principal Investigator: AYÇA TAŞ TUNA, Professor, M.D., Sakarya University Faculty of Medicine

Publications and helpful links

General Publications

• Meybohm P, Gruenewald M, Hocker J, Renner J, Graesner JT, Ilies C, Scholz J, Bein B. Correlation and agreement between the bispectral index vs. state entropy during hypothermic cardio-pulmonary bypass. Acta Anaesthesiol Scand. 2010 Feb;54(2):169-75. doi: 10.1111/j.1399-6576.2009.02138.x. Epub 2009 Oct 15.
• Belletti A, Lee DK, Yanase F, Naorungroj T, Eastwood GM, Bellomo R, Weinberg L. Changes in SedLine-derived processed electroencephalographic parameters during hypothermia in patients undergoing cardiac surgery with cardiopulmonary bypass. Front Cardiovasc Med. 2023 Jul 4;10:1084426. doi: 10.3389/fcvm.2023.1084426. eCollection 2023.

Study record dates

Study Major Dates

• Study Start (Actual): May 1, 2026
• Primary Completion (Estimated): August 1, 2026
• Study Completion (Estimated): December 31, 2026

Study Registration Dates

• First Submitted: March 27, 2026
• First Submitted That Met QC Criteria: March 27, 2026
• First Posted (Actual): April 2, 2026

Study Record Updates

• Last Update Posted (Actual): May 11, 2026
• Last Update Submitted That Met QC Criteria: May 5, 2026
• Last Verified: May 1, 2026

More Information

Terms related to this study

• Keywords: Cardiac Surgery; Bispectral Index; Intraoperative Monitoring; Depth of Anesthesia; Patient State Index; Processed EEG; Hypothermic CPB
• Additional Relevant MeSH Terms: Body Temperature Changes; Pathological Conditions, Signs and Symptoms; Signs and Symptoms; Hypothermia
• Other Study ID Numbers: SEAH-DOAonCPB-2026

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: UNDECIDED
• IPD Plan Description: Individual participant data may be shared upon reasonable request, subject to approval by the institutional ethics committee and in accordance with applicable data protection regulations. At the time of registration, a definitive data sharing plan has not been finalized.

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No