Electroencephalogram (EEG) in General Anaesthesia - More Than Only a Bispectral Index (BIS)

Processed electroencephalogram (EEG) monitors are routinely used in addition to clinical parameters to assess the depth of anaesthesia during general anaesthesia. In addition to the bispectral (BIS) index displayed as an index, the raw frontal EEG can be displayed as a curve on these monitors. After a short training, anaesthetists might be more accurate and faster in assessing depth of anaesthesia by recognizing the pattern of the EEG curve than by using the BIS index. This may further enhance the positive effects that could be demonstrated for the use of BIS monitors.

Therefore, the aim of the investigator's study is to investigate the clinical relevance of interpreting the raw frontal EEG in addition to only using the BIS index for titrating intravenous anaesthetics.

Inclusion criteria

• Adult patients undergoing in-hospital laparoscopic abdominal surgery with general anaesthesia using Propofol based on the Schnider model (target controlled infusion)42, 43
• Minimal duration of surgery of 60 minutes
• Written informed consent

Exclusion criteria

• Same-day surgery
• Language barrier
• Patients under 18 years of age
• Pregnancy (using a beta-human chorionic gonadotropin (HCG) measurement in a blood sample of women in childbearing age)
• Allergy to Propofol
• Administration of hypnotics other than Propofol, such as ketamine or midazolam preoperatively or intraoperatively
• Known brain pathology, such as seizure disorders, dementia, cerebrovascular disease or brain death