BIS Variability and Change in Quality of Recovery After Surgery

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

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.

Study Overview

• Status: Recruiting
• Conditions: Cholecystectomy, Laparoscopic; Bispectral Index Variability During General Anesthesia and Postoperative Recovery

Detailed Description

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.

• Study Type: Observational
• Enrollment (Estimated): 126

Contacts and Locations

• Study Contact: Name: AHMET R DOĞAN, M.D; Phone Number: +905427988070; Email: a.ridvandogan@gmail.com
• Study Contact Backup: Name: Ayça Taş Tuna, Prof. Dr; Phone Number: +90 532 300 48 26; Email: aycatas@yahoo.com

Study Locations

• Turkey (Türkiye)
  • Serdivan
    • Sakarya, Serdivan, Turkey (Türkiye), 54000
      • Recruiting
      • Sakarya University Training and Research Hospital, Department of Anesthesiology and Reanimation
      • Principal Investigator: AYÇA TAŞ TUNA, Professor, M.D.
      • Contact: AHMET R DOĞAN, M.D; Phone Number: +905427988070; Email: a.ridvandogan@gmail.com
      • Sub-Investigator: AHMET R DOĞAN, M.D

Participation Criteria

Eligibility Criteria

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

• Sampling Method: Non-Probability Sample

Study Population

The study population consists of adult patients aged 18 to 65 years undergoing elective laparoscopic cholecystectomy under general anesthesia. All participants will receive routine perioperative care according to standard clinical practice, including intraoperative bispectral index (BIS) monitoring. The study includes a single prospective observational cohort, and no experimental intervention or alteration of standard anesthesia management will be performed. Participants will be assessed preoperatively and postoperatively to evaluate changes in recovery quality following surgery.

Description

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

Study Plan

How is the study designed?

Number of groups / cohorts

1

Cohorts and Interventions

Group / Cohort

Elective Laporoscopic Cholecystectomy Patients Undergoing General Anesthesia; This cohort consists of adult patients undergoing elective laparoscopic cholecystectomy under general anesthesia. All participants will receive routine anesthetic management according to standard clinical practice. No experimental intervention or protocol-driven modification of anesthesia care will be applied. Intraoperative bispectral index (BIS) monitoring will be used as part of standard anesthesia monitoring. BIS data and routine perioperative clinical variables will be recorded for observational analysis. Postoperative recovery will be assessed using validated questionnaires administered before surgery and on postoperative day one. The study involves a single observational cohort without a comparison or control group.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Change in Quality of Recovery-15 (ΔQoR-15) Score	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).	From preoperative baseline to postoperative day one

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Incidence of Postoperative Delirium (Nu-DESC ≥ 2)	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 (%).	From preoperative baseline to early postoperative recovery in the post-anesthesia care unit (PACU), within the first 2 hours after anesthesia
Postoperative Pain Intensity (VAS)	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.	Postoperative day 1

Collaborators and Investigators

• Sponsor: Sakarya University
• Investigators: Principal Investigator: Ayca Tas Tuna, Professor, M.D., Sakarya University Faculty of Medicine

Study record dates

Study Major Dates

• Study Start (Actual): January 1, 2026
• Primary Completion (Estimated): May 1, 2026
• Study Completion (Estimated): December 30, 2026

Study Registration Dates

• First Submitted: February 18, 2026
• First Submitted That Met QC Criteria: March 3, 2026
• First Posted (Actual): March 6, 2026

Study Record Updates

• Last Update Posted (Actual): April 8, 2026
• Last Update Submitted That Met QC Criteria: April 2, 2026
• Last Verified: April 1, 2026

More Information

Terms related to this study

• Keywords: Quality of Recovery; General Anesthesia; Bispectral Index; Postoperative Recovery; Anesthesia Depth; Bispectral Index Variability
• Other Study ID Numbers: SEAH-BISVARIABILITY-2026

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: UNDECIDED
• IPD Plan Description: Individual participant data (IPD) sharing plans have not yet been determined. Decisions regarding data sharing will depend on institutional policies, ethical considerations, and data anonymization requirements, and may be addressed following completion of the study and primary analyses.

Drug and device information, study documents

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