Comparison of the Factors Affecting PSI and BIS Values in Monitoring Anesthetic Depth During Open-Heart Surgery

Measurement of anesthetic depth has long been a subject of investigation, aiming to titrate anesthetic agents appropriately and to prevent intraoperative awareness and consciousness. Many patients undergoing surgery experience fear and anxiety regarding the possibility of remaining conscious, perceiving pain, and being unable to move during anesthesia. Intraoperative awareness-defined as consciousness during anesthesia with explicit recall afterward-is a distressing condition that can lead to post-traumatic stress disorder.

However, aiming for excessively deep anesthesia to avoid the possibility of awareness during surgery is not recommended, as it may result in hemodynamic instability due to the effects of anesthetic agents and may impair postoperative cognitive functions, particularly in the elderly population.

Common methods used in monitoring anesthetic depth include observing sweating, lacrimation, pupillary dilation, heart rate variability, and blood pressure. However, some of these are subjective and may not always be reliable indicators.

Electroencephalogram (EEG)-based monitors such as the Bispectral Index (BIS) and the Patient State Index (PSI) offer more reliable and objective means of monitoring anesthetic depth. These monitors provide numerical values between 0 (indicating unconsciousness) and 100 (indicating full alertness) based on proprietary algorithms, offering valuable insight into the patient's anesthetic state.

"Our aim is to examine BIS and PSI values and to investigate the factors that influence these parameters."

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Key information

Conditions

BIS-EEG Anesthesia Depth Monitoring Open Heart Surgery PSI

Age range

18 year–65 year

Sex eligibility

All sexes

Study type

Observational

Primary location

Kocaeli University

Köseköy, Kocaeli, 41000, Turkey (Türkiye)

Who can participate

Only the study team can determine whether someone qualifies for participation.

Inclusion criteria

"Patients aged 18 to 65 years,
Classified as ASA (American Society of Anesthesiologists) physical status II-III,
scheduled for elective open-heart surgery via median sternotomy

Exclusion criteria

"Patients with an ejection fraction below 35%,
Those with pre-existing central nervous system disorders (e.g., history of epileptic seizures or intracranial space-occupying lesions),
A history of prior open cranial surgery,
Known allergies to anesthetic agents, alcohol or substance abuse,
Any other conditions deemed to negatively affect the BIS profile (e.g., patients with preoperative intra-aortic balloon pump insertion, those undergoing surgery under inotropic support, or receiving preoperative sedative infusions),
As well as patients scheduled to undergo antegrade or retrograde cerebral perfusion or total circulatory arrest

Treatment and study plan

anesthesia depth monitorizing, awareness

Device

Investigation of BIS and PSI Monitoring Methods for Anesthetic Depth and the Factors Affecting These Methods in Open-Heart Surgery

Primary outcomes

The primary objective of this study is to measure the correlation between BIS and PSI values, which are parameters used to monitor the depth of anesthesia during open-heart surgery.

Time frame: Data will be collected over a 12-month period and subjected to statistical analysis.

BIS (Bispectral Index) is a monitoring method that uses EEG (electroencephalogram) data to measure the depth of anesthesia. It has been used for a long time to assess anesthetic depth. PSI (Patient State Index) is a monitoring method that has become more popular in recent years for measuring the depth of anesthesia. The recommended reference ranges for anesthetic depth are 40-60 for BIS and 25-50 for PSI. The primary objective of this study is to measure the correlation between PSI and BIS values during open-heart surgery.

Secondary outcomes

The secondary objective of this study is to measure the effect of hypothermia, which develops after patients are connected to the cardiopulmonary bypass (CPB) machine during open-heart surgery, on BIS and PSI values that indicate the depth of anesthesia

Time frame: Data will be collected over a 12-month period and subjected to statistical analysis.

BIS is a monitoring method that uses EEG (electroencephalogram) data to measure the depth of anesthesia. It has been used for a long time for this purpose. PSI is a monitoring method that has become more popular in recent years for assessing anesthetic depth. The recommended reference ranges for anesthetic depth are 40-60 for BIS and 25-50 for PSI. In the literature, there are studies suggesting that the decrease in body temperature (hypothermia) during cardiopulmonary bypass (CPB) in open-heart surgery is similar to the decrease observed in BIS and PSI values. In this study, our secondary objective is to measure the similarity between the decrease in body temperature and the decrease in BIS and PSI values.

Sponsors and collaborators

Lead sponsor

Kocaeli University

Other

Registry information

Important dates

Study start: 2024
Primary completion: 2025
Study completion: 2025
First posted: Jun 29, 2025
Registry last updated: Jun 29, 2025

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This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.

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