BIS Variability and Change in Quality of Recovery After Surgery

Overview

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.

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.