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NCT Number: NCT07454629

BIS Variability and Change in Quality of Recovery After Surgery

This prospective observational study aims to examine the relationship between fluctuations in anesthesia depth, measured by bispectral index (BIS) monitoring during surgery, and changes in patients' postoperative recovery quality.

BIS monitoring is routinely used during general anesthesia to assess the depth of anesthesia, but BIS values often fluctuate over time rather than remaining stable. The clinical significance of this variability is not well understood. In this study, BIS variability during anesthesia induction and maintenance will be evaluated and compared with changes in postoperative recovery quality.

Recovery quality will be assessed using the Quality of Recovery-15 (QoR-15) questionnaire, which will be administered before surgery and again on the first postoperative day. The primary outcome of the study will be the change in QoR-15 score from the preoperative baseline to postoperative day one (ΔQoR-15). Delirium screening and routine perioperative clinical data will also be collected.

No additional interventions beyond standard anesthesia care will be performed. The results of this study may help improve understanding of how intraoperative anesthesia stability relates to patient recovery after surgery.

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Key information

Conditions

Bispectral Index Variability During General Anesthesia and Postoperative Recovery Cholecystectomy, Laparoscopic

Age range

18 year–65 year

Sex eligibility

All sexes

Study type

Observational

Primary location

Sakarya University Training and Research Hospital, Department of Anesthesiology and Reanimation

Sakarya, Serdivan, 54000, Turkey (Türkiye)

About this study

Bispectral index (BIS) monitoring is widely used in routine anesthesia practice to assess anesthetic depth using processed electroencephalographic signals. Although absolute BIS values are commonly targeted during anesthesia, BIS readings frequently exhibit intraoperative fluctuations rather than remaining stable. The clinical relevance of this variability, particularly in relation to postoperative recovery outcomes, remains insufficiently characterized.

This prospective observational study is designed to evaluate the association between intraoperative BIS variability and changes in postoperative recovery quality. Adult patients undergoing elective laparoscopic cholecystectomy under standardized general anesthesia will be included. No experimental intervention or protocol-driven modification of anesthetic management will be applied beyond routine clinical care.

BIS data will be obtained as part of standard anesthesia monitoring and exported from the BIS monitor at the end of each procedure. Only BIS measurements meeting predefined signal quality criteria will be included in the analysis. BIS variability will be quantified using statistical dispersion measures derived from filtered BIS data during predefined anesthesia phases, including induction and maintenance.

Postoperative recovery quality will be assessed using the Quality of Recovery-15 (QoR-15) questionnaire. QoR-15 will be administered preoperatively to establish baseline status and repeated on postoperative day one. The primary outcome will be defined as the change in QoR-15 score from baseline to postoperative day one (ΔQoR-15). Screening for postoperative delirium and routine perioperative clinical variables will be collected as secondary or exploratory outcomes.

Statistical analyses will focus on assessing the association between BIS variability metrics and ΔQoR-15, with additional analyses performed to account for relevant perioperative variables. The findings of this study are expected to contribute to a better understanding of how intraoperative anesthetic stability relates to patient-centered recovery outcomes following surgery.

Who can participate

Healthy volunteers accepted: No

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

Inclusion criteria

  • Adults aged 18 to 65 years
  • Scheduled for elective laparoscopic cholecystectomy
  • American Society of Anesthesiologists (ASA) physical status I-III
  • Planned general anesthesia with routine bispectral index (BIS) monitoring
  • Ability to provide written informed consent

Exclusion criteria

  • History of neurological disease
  • Use of neuropsychiatric medications
  • Cognitive impairment or mental retardation
  • Inability to complete the Quality of Recovery-15 (QoR-15) questionnaire

Treatment and study plan

Primary outcomes

  1. Change in Quality of Recovery-15 (ΔQoR-15) Score

    Time frame: From preoperative baseline to postoperative day one

    The primary outcome is the change in postoperative recovery quality measured using the Quality of Recovery-15 (QoR-15) questionnaire. ΔQoR-15 is defined as the difference between the postoperative day one QoR-15 total score and the preoperative baseline QoR-15 total score. The QoR-15 is a validated 15-item questionnaire with total scores ranging from 0 to 150 points, where higher scores indicate better recovery quality. ΔQoR-15 will be analyzed as a continuous variable (points).

Secondary outcomes

  1. Incidence of Postoperative Delirium (Nu-DESC ≥ 2)

    Time frame: From preoperative baseline to early postoperative recovery in the post-anesthesia care unit (PACU), within the first 2 hours after anesthesia

    Postoperative delirium will be assessed using the Nursing Delirium Screening Scale (Nu-DESC). Delirium will be defined as a Nu-DESC total score ≥ 2 during early postoperative recovery in the PACU. The outcome will be reported as the percentage of patients meeting delirium criteria (%).

  2. Postoperative Pain Intensity (VAS)

    Time frame: Postoperative day 1

    Postoperative pain intensity will be assessed using a visual analog scale (VAS) as part of routine clinical evaluation during the early postoperative period. The relationship between intraoperative BIS variability and postoperative pain scores will be explored as a secondary outcome.

Sponsors and collaborators

Lead sponsor

Sakarya University

Other

Registry information

Official study title

Association Between Intraoperative Bispectral Index Variability and Change in Quality of Recovery-15 Score: A Prospective Observational Study

Important dates

Study start
2026
Primary completion
2026
Study completion
2026
First posted
Mar 6, 2026
Registry last updated
Sep 2, 2026

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

View the official ClinicalTrials.gov record (opens in a new tab)

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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