SedLine® Brain Function Monitoring provides real-time insight into a patient's depth of anesthesia with bilateral data acquisition and processing of electroencephalogram (EEG) signals. Four active EEG leads collect data from the frontal lobe with a sensor position on the patient's forehead.

Whenever a frontal approach for neurosurgical procedures is required or the frontal placement of the EEG is not indicated, it would not be possible to place the SedLine® .

Numerous studies have analyzed the change of position and the application of alternative positions for other devices used in assessing the depth of anesthesia. Albeit, yet to date, there is no study that analyzed the application of alternative positions for the SedLine® sensor.

The purpose of study is to compare the standard forehead placement versus a nasal placement of SedLine® sensor for neuromonitoring.

The hypothesis is that placing the central sensors in the montage approximately 2 cm below the standard recommended placement, across the nasal bridge and then running under the eyes to the normal temporal leads placement would put the entire montage out of the operative field and would still have corresponding values and EEG signals.

The primary outcome measure is to monitor and compare processed electroencephalograph (EEG) values (PSi- Patient State Index, SEFL- Spectral Edge Frequency Left, SEFR- Spectral Edge Frequency Right, SR-Suppression Ratio, EMG-Electromyography, ARTF-Artifact) and EEG waveforms, on both sensors (standard-Forehead and alternative-Nasal)

Other parameters that will be measure are patient demographics (age, sex, surgery, ASA status, weight, height, BMI).

Inclusion Criteria:

• Patients older than 18 years of age, both genders.
• Patients undergoing simple or complex surgery.
• American Society of Anesthesiologists Classification (ASA) score I to III.

Exclusion Criteria:

American Society of Anesthesiologists Classification (ASA) score IV and V.

• Emergency cases
• Cognitive/Mentally impaired or unable to provide consent
• Previous neurological problems affecting EEG
• Dementia
• Use of sedative or drugs that can alter EEG readings
• Patients under head and neck surgery

For each of the two modes of measurement, 1800 data points per subject (1 reading every 2 seconds for 1 hour) per hour will be collected. Assuming a maximum interclass correlation coefficient of .90, a sample size of 40 patients will be required to test the null hypotheses that the two modes of measurement share 95% of their variance via the construction of a 95% confidence interval that ranges no more than +/-5%.

Data from the 2 placements will be compared and analyzed using a Bland-Altman analysis, a Scatter plot analysis, and a matched-pair analysis.