This prospective, single-center, randomized interventional study aims to investigate the effects of commonly used adjunct anesthetic drugs on the Bispectral Index (BIS) and electroencephalographic (EEG) activity during total intravenous anesthesia.
BIS monitoring is widely used to estimate the depth of anesthesia. However, previous studies suggest that certain anesthetic drugs, particularly dexmedetomidine and esketamine, may alter BIS values independently of the patient's actual level of consciousness. As a result, BIS readings may not always accurately reflect anesthetic depth when multiple drugs are administered together.
Adult patients undergoing elective laparoscopic cholecystectomy under standardized propofol-remifentanil anesthesia will be randomly assigned to receive one of the following adjunct drugs: midazolam, dexmedetomidine, esketamine, or no additional study drug (control group). Continuous BIS values and raw EEG signals will be recorded throughout the study period.
The primary objective is to compare changes in BIS values among different adjunct anesthetic drugs under otherwise similar anesthetic conditions. The study will also explore corresponding EEG characteristics associated with these changes. The findings are expected to improve understanding of drug-related differences in processed EEG monitoring and provide data for future development of more accurate anesthesia depth assessment methods.
ASA physical status I-II;
BMI 18-28 kg/m²;
Scheduled for elective laparoscopic cholecystectomy, with an expected surgical duration from skin incision to completion of wound closure of ≥45 min;
Planned to receive propofol-remifentanil total intravenous anesthesia, with routine intraoperative BIS monitoring and simultaneous acquisition of raw EEG signals;
A confirmed history of psychiatric or neurological disorders, or use of antipsychotics, antidepressants, benzodiazepines, or other sedative-hypnotic drugs within 4 weeks before surgery;
Cognitive impairment identified by Mini-Cog screening;
Poorly controlled or untreated hypertension, sinus bradycardia, or severe cardiac conduction block;
Acute angle-closure glaucoma;
Parallel
Midazolam
DrugMidazolam administered as an adjunct to standardized propofol-remifentanil total intravenous anesthesia according to the study protocol.
Dexmedetomidine
DrugDexmedetomidine administered as an adjunct to standardized propofol-remifentanil total intravenous anesthesia according to the study protocol.
Esketamine
DrugEsketamine administered as an adjunct to standardized propofol-remifentanil total intravenous anesthesia according to the study protocol.
Propofol
DrugPropofol will be administered as part of standardized total intravenous anesthesia in all study groups.
Remifentanil
DrugRemifentanil will be administered as part of standardized total intravenous anesthesia in all study groups.
Change in Bispectral Index (BIS) value from the pre-intervention baseline
Change in Bispectral Index value from the stable pre-intervention baseline will be compared among the four study groups after administration of the assigned adjunct anesthetic drug under standardized propofol-remifentanil total intravenous anesthesia. The pre-intervention baseline is defined as the stable BIS value immediately before administration of the assigned adjunct anesthetic drug. The Bispectral Index is a dimensionless electroencephalography-derived index ranging from 0 to 100, with lower values indicating deeper hypnotic states.
Change in mean arterial pressure from pre-intervention baseline
Change in mean arterial pressure (MAP) from the stable pre-intervention baseline will be compared among the four study groups after administration of the assigned adjunct anesthetic drug under standardized propofol-remifentanil total intravenous anesthesia.
Change in heart rate from pre-intervention baseline
Change in heart rate (HR) from the stable pre-intervention baseline will be compared among the four study groups after administration of the assigned adjunct anesthetic drug.
Time from discontinuation of anesthetic drugs to airway device removal
The time interval from discontinuation of anesthetic drugs to removal of the airway device will be recorded.
Time to Aldrete score of 10 in the post-anesthesia care unit
The time from admission to the post-anesthesia care unit to achievement of an Aldrete score of 10 will be recorded. The Aldrete score ranges from 0 to 10, with higher scores indicating better post-anesthesia recovery.
Change in pre-specified electroencephalographic spectral features from baseline
Pre-specified electroencephalographic spectral features, including alpha-to-delta power ratio, frontal alpha power, alpha peak frequency, and burst suppression ratio, will be evaluated and compared among study groups at baseline and after administration of the assigned adjunct anesthetic drug.
Change in electroencephalographic relative spectral power from baseline
Relative power spectral density of delta, theta, alpha, beta, and gamma frequency bands will be compared among study groups at baseline and after administration of the assigned adjunct anesthetic drug.
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