The goal of this randomized controlled trial is to evaluate whether the PRST (Evans) score is a valid method for monitoring the depth of general anesthesia in adult surgical patients. It will also assess whether combining the PRST score with Bispectral Index (BIS) monitoring improves anesthetic depth assessment compared with PRST-guided monitoring alone.

The main questions it aims to answer are:

1. Does the PRST score correlate with BIS values during general anesthesia?
2. Does visible BIS-guided monitoring improve anesthetic depth assessment compared with PRST-guided monitoring alone?

Researchers will compare patients managed using PRST-guided monitoring alone with patients managed using PRST plus visible BIS-guided monitoring.

Participants will:

1. Undergo elective surgery under general anesthesia
2. Receive intraoperative anesthetic depth monitoring using PRST score alone or PRST combined with BIS monitoring
3. Have PRST score, BIS, heart rate, and blood pressure recorded at predefined intraoperative timepoints
4. Complete a postoperative interview assessing recall, dreaming, and anesthesia-related discomfort

This single-center, parallel-group randomized controlled trial (RCT) aims to evaluate the validity of the PRST (Evans) score for monitoring the depth of general anesthesia and to assess its relationship with Bispectral Index (BIS) monitoring in adult surgical patients undergoing elective procedures under general anesthesia.

Intraoperative awareness remains a clinically important complication during general anesthesia. Traditional clinical assessment methods such as the PRST score evaluate autonomic responses including systolic blood pressure, heart rate, sweating, and lacrimation, whereas BIS provides an electroencephalography-based objective assessment of hypnotic depth. This study investigates whether combining PRST assessment with BIS monitoring may improve anesthetic depth evaluation compared with PRST-guided monitoring alone.

Eligible participants are randomized into either a PRST-guided monitoring group or a PRST plus visible BIS-guided monitoring group. Standard anesthetic induction and maintenance protocols are applied in both groups. In the intervention group, BIS monitoring is used as an adjunctive tool to guide anesthetic depth management, with a target BIS range of 40-60.

PRST score, BIS values, heart rate (HR), and mean arterial pressure (MAP) are recorded at predefined intraoperative timepoints including T0 (baseline before induction), T1 (after induction before laryngoscopy), T2 (1-3 minutes after airway instrumentation), T3 (before skin incision), T4 (5 minutes after incision), and T5-T6 (15 and 30 minutes during the maintenance phase). Postoperative interviews are conducted to evaluate recall, dreaming, and anesthesia-related discomfort.

The primary objective is to determine the association between PRST score and BIS values during general anesthesia. Secondary objectives include evaluation of hemodynamic responses, anesthetic delivery variables, postoperative recall-related events, and the diagnostic performance of PRST score in identifying BIS-defined light anesthesia.

Inclusion Criteria:

• Scheduled for elective surgery under general anesthesia

Exclusion Criteria:

• Unstable hemodynamic conditions
• Contraindications to specific anesthetic agents or significant neurological disorders (e.g., Parkinson's disease, stroke, or dementia)
• Receiving medications known to influence EEG activity, such as anticonvulsants
• Unable to provide informed consent