In this trial, investigators aimed to compared the clinical effects between the electroencephalographic (EEG) spetrogram-guided and processed EEG index-guided multimodal general anesthesia using the combination of propofol, dexmedetomidine, remifentnil and the scalp block in patients undergoing elective craniotomy.

The multimodal general anesthesia involved the administration of combinations of antinociceptive agents and hypnotics using electroencephalographic (EEG) based monitors to achieve a balanced state of anesthesia. Traditionally, the adjustment of general anesthesia drugs has been done using instruments like the Bispectral Index (BIS), which converts frontal lobe EEG signals into a numerical range of 0-100. This allows anesthesiologists to assess drug dosage and depth of anesthesia. However, numerical conversion may not accurately reflect individual variations and cannot precisely calculate drug concentrations in the case of multiple drug combinations.

For instance, dexmedetomidine (DEX) is currently one of the most commonly used drugs in multimodal generagal anesthesia.Because each anesthetic produces distinct brain states that are readily visible in an EEG density spectral array (DSA) and can be easily interpreted by anesthesiologists, anesthetic titration based on an EEG DSA may provide additional information for anesthetic depth monitoring and may avoid the conventional 'one-index-fits-all' approach, which often ignores the influence of anesthetic drug combination. Theoretically, the anesthetic exposure in cases that involve the coadministration of dexmedetomidine can be more precise through the use of an EEG DSA than the use of BIS value. In accordant to this context, investigators have changed our institutional anesthetic propofol from BIS guidance to the DSA guidance and based on the retrospective analysis, investigators further observed the profound anesthetic-sparing effects and potential postoperative benefits of EEG DSA-guided anesthesia comparing to the BIS-guided anesthesia (doi: 10.4097/kja.23118). Therefore, further prospective randomized controlled is warranted to shape the real clinical benefits of DSA-guided multimodal general anesthesia.

Inclusion Criteria:

• patients undergoing elective craniotomy

Exclusion Criteria:

• revision surgery
• heart failure
• liver cirrhosis > Child B class
• chronic obstructive pulmonary disease