Validation of a nasal SedLine® sensor placement: Going beyond the forehead when depth of anesthesia is important

Abstract

Introduction: Since the inception of general anesthesia, the assessment of anesthetic depth has been challenging and a goal that anesthesiologists constantly strive for. Nowadays, an increasing number of monitors allow us to have a more specific assessment of depth of anesthesia. However, the conventional sensor-lead positioning on the forehead recommended by manufacturers may sometimes coincide with the surgical field thereby posing a clinical challenge. This study compares the conventional frontal placement on the forehead with an experimental nasal placement for the standard Masimo SedLine® EEG sensor in surgical neuromonitoring, analyzing and comparing numeric values (Patient State Index-PSi) and EEG waveform traces. Methods: Authors performed a single-center, observational, prospective study enrolling 40 patients under a standardized anesthesia protocol. Three contiguous time periods (induction, steady-state anesthesia and awakening) were used to stratify data analysis so that within-patient correlations between nasal and frontal readings could be examined by time period independently. Results: A total of 106,209 matched numeric values and 3,543 min of EEG data from each sensor’s positions were collected from 40 patients. Total average alignment between two sensor positions, keeping in mind that 5 PSi units were used as acceptable limit of agreement, was 83.01% and p-values associated with R2 correlation coefficients were statistically significant at 0.001 level. Steady-state anesthesia phase alignment (with full muscle-relaxation), which present 73% of all collected data, show a concordance within 5 PSi unit alignment in 95.77%. One hundred and twenty tracings from 40 patients were presented to two epileptologists and inter-rater agreement or reliability was achieved in 88% of EEG-traces’ analysis. Conclusions: The current results suggest that SedLine® Brain Function Monitoring sensor is acceptable for clinical use when standard sensor position in the forehead is not possible. This allows for the possibility of utilization of the sensor whenever the forehead placement cannot be utilized.

Keywords

• Depth of anesthesia
• Electroencephalography
• Alternative SedLine® sensor position