Subcostal TAP Block and EEG Dynamics in Laparoscopic Cholecystectomy

This is a prospective, single-center observational study including adult patients scheduled for laparoscopic cholecystectomy under general anesthesia. The study will be conducted at Sancaktepe Sehit Prof. Dr. Ilhan Varank Training and Research Hospital.

Perioperative analgesic management will be determined by the attending anesthesiologist according to routine clinical practice and will not be assigned by the study protocol. Patients will subsequently be evaluated in two observational groups according to the analgesic technique received. One group will consist of patients receiving intravenous remifentanil infusion without a subcostal TAP block, while the other group will consist of patients receiving intravenous remifentanil infusion together with an ultrasound-guided subcostal TAP block.

General anesthesia will be maintained using sevoflurane and remifentanil according to routine clinical practice. Depth of anesthesia and cerebral electrical activity will be monitored using Bispectral Index (BIS) monitoring and electroencephalography (EEG). Intraoperative EEG characteristics, including changes in alpha-band activity and burst suppression, as well as BIS values, will be recorded and compared between the two groups.

Intraoperative analgesic consumption, including remifentanil and additional fentanyl use, will be recorded from anesthesia records. Hemodynamic responses and other routinely monitored parameters will also be documented.

Postoperative pain will be evaluated using the Numerical Rating Scale (NRS) at rest and during activity at 0, 1, 4, 8, 12, and 24 hours after surgery. Routine postoperative analgesia includes intravenous paracetamol and tenoxicam. When clinically indicated for inadequate pain control, rescue analgesia with intravenous tramadol may be administered according to routine clinical practice, and additional analgesic consumption will be recorded.

Postoperative recovery will additionally be assessed using the 15-item Quality of Recovery questionnaire (QoR-15). Mobilization time, length of hospital stay, and patient satisfaction will also be recorded.

The primary objective of the study is to evaluate the association between subcostal TAP block use and intraoperative analgesic requirements, anesthetic depth, EEG dynamics, and burst suppression. Secondary objectives include comparison of postoperative pain, additional analgesic consumption, quality of recovery, mobilization time, length of hospital stay, and patient satisfaction between the two groups.

Inclusion criteria

• Age 18 years or older
• American Society of Anesthesiologists (ASA) physical status I-III
• Scheduled to undergo laparoscopic cholecystectomy under general anesthesia
• Written informed consent provided by the participant or, when applicable, the legally authorized representative

Exclusion criteria

• Refusal to participate in the study
• American Society of Anesthesiologists (ASA) physical status IV-V
• Known allergy or hypersensitivity to medications used during perioperative anesthetic or analgesic management