The goal of this clinical trial is to determine the appropriate Bispectral Index (BIS) range and propofol effect-site concentration required to maintain adequate anesthesia depth during total intravenous anesthesia (TIVA) combined with midazolam, dexmedetomidine, or esketamine in patients undergoing unilateral knee replacement surgery. The main questions it aims to answer are:
1. What are the appropriate BIS range and propofol effect-site concentration for maintaining adequate anesthesia depth when combined with each of the three medications (midazolam, dexmedetomidine, or esketamine) during TIVA? 2. How these combination regimens affect the quality of recovery and postoperative pain in patients？
Participants will:
1. Receive one of four anesthesia regimens during surgery: propofol alone, propofol combined with midazolam, dexmedetomidine, or esketamine. 2. Undergo a stepwise reduction of propofol effect-site concentration towards the end of surgery. 3. Have their consciousness assessed using the isolated forearm technique, while BIS, EEG signals, and vital signs are continuously monitored throughout the procedure. 4. Have their recovery quality and postoperative pain assessed after surgery.
Age 18 to 65 years
American Society of Anesthesiologists (ASA) physical status I or II
Body Mass Index (BMI) 18 to 30 kg/m²
Scheduled for elective unilateral total knee replacement surgery
History of neurological disorders
Cognitive dysfunction assessed by the Mini-Cog scale
History of antipsychotic or sedative medication use in the past 4 weeks
Poorly controlled or untreated hypertension
Parallel
Propofol + Remifentanil +Midazolam
DrugParticipants in this arm will receive total intravenous anesthesia (TIVA) with propofol and remifentanil during the maintenance period. After placement of the knee prosthesis, the isolated forearm technique (IFT) will be initiated. Participants will wear headphones playing recorded standardized instructions. Rocuronium (0.3 mg/kg) will be administered via the non-dominant arm. Midazolam (2 mg) will be administered intravenously.The propofol plasma-site concentration will be set to 1.8 μg/mL, then reduced in stepwise decrements of 0.3 μg/mL, with each concentration maintained for 5 minutes, until any of the following endpoints is reached: (1) positive IFT response , (2) BIS \> 60 sustained for 1 minute, (3) electroencephalogram signs of arousal, or (4) clinical judgment by the anesthesiologist that anesthesia depth is inadequate.
Propofol + Remifentanil + Dexmedetomidine
DrugParticipants in this arm will receive total intravenous anesthesia (TIVA) with propofol and remifentanil during the maintenance period. After placement of the knee prosthesis, the isolated forearm technique (IFT) will be initiated. Participants will wear headphones playing recorded standardized instructions. Rocuronium (0.3 mg/kg) will be administered via the non-dominant arm. Dexmedetomidine 1 μg/kg infused over 10 minutes.The propofol plasma-site concentration will be set to 1.8 μg/mL, then reduced in stepwise decrements of 0.3 μg/mL, with each concentration maintained for 5 minutes, until any of the following endpoints is reached: (1) positive IFT response , (2) BIS \> 60 sustained for 1 minute, (3) electroencephalogram signs of arousal, or (4) clinical judgment by the anesthesiologist that anesthesia depth is inadequate.
Propofol + Remifentanil + Esketamine
DrugParticipants in this arm will receive total intravenous anesthesia (TIVA) with propofol and remifentanil during the maintenance period. After placement of the knee prosthesis, the isolated forearm technique (IFT) will be initiated. Participants will wear headphones playing recorded standardized instructions. Rocuronium (0.3 mg/kg) will be administered via the non-dominant arm. Esketamine (0.3 mg/kg) will be administered intravenously.The propofol plasma-site concentration will be set to 1.8 μg/mL, then reduced in stepwise decrements of 0.3 μg/mL, with each concentration maintained for 5 minutes, until any of the following endpoints is reached: (1) positive IFT response , (2) BIS \> 75 sustained for 1 minute, (3) electroencephalogram signs of arousal, or (4) clinical judgment by the anesthesiologist that anesthesia depth is inadequate.
Propofol + Remifentanil
DrugParticipants in this arm will receive total intravenous anesthesia (TIVA) with propofol and remifentanil during the maintenance period. After placement of the knee prosthesis, the isolated forearm technique (IFT) will be initiated. Participants will wear headphones playing recorded standardized instructions. Rocuronium (0.3 mg/kg) will be administered via the non-dominant arm. The propofol plasma-site concentration will be reduced in stepwise decrements of 0.3 μg/mL, with each concentration maintained for 5 minutes, until any of the following endpoints is reached: (1) positive IFT response , (2) BIS \> 60 sustained for 1 minute, (3) electroencephalogram signs of arousal, or (4) clinical judgment by the anesthesiologist that anesthesia depth is inadequate.
BIS value
BIS value recorded at the first occurrence of IFT positivity or any predefined clinical sign of inadequate anesthesia.
Propofol Effect-Site Concentration
Propofol effect-site concentration recorded at the first occurrence of IFT positivity or any predefined clinical sign of inadequate anesthesia.
Modified Brice Questionnaire
The presence of intra-operative awareness with recall is assessed using the Modified Brice Questionnaire. The questionnaire explores the patient's memory of the peri-operative period through structured questions.
Time from Discontinuation of Anesthetics to Laryngeal Mask Airway Removal
From discontinuation of anesthetics to LMA removal. Successful removal is defined as the patient being awake, able to open mouth on command, and having return of protective reflexes, without signs of respiratory distress.
Time to Modified Aldrete Score of 10 in the Post Anesthesia Care Unit
Time from post anesthesia care unit (PACU) admission until the first attainment of a Modified Aldrete Score of 10. The Modified Aldrete Score assesses five domains: consciousness, activity, respiration, blood pressure, and oxygen saturation, each scored from 0 to 2, with a maximum total score of 10. A score of 10 indicates the patient has achieved optimal recovery in all five domains.
Adverse Events During Emergence from Anesthesia
Adverse events during the period from anesthetic discontinuation to PACU discharge are recorded.
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