Comparison of Nasal and Frontal BIS Monitoring in Neurosurgery: Does the Site of Sensor Placement Affect the BIS Values?

Background and Goal of Study: Intraoperative awareness is a serious but preventable complication of general anaesthesia. Bispectral index (BIS) is the most widely used method monitoring anaesthesia depth. BIS monitoring requires attachment of forehead sensors, which poses a challenge when the surgical field involves the forehead. We aimed to compare the gold standard forehead position of BIS sensors with an alternative position across the nasal dorsum for neurosurgical procedures. Materials and Methods: After ethical committee approval and informed consent were obtained, 62 patients were enrolled in this prospective observational study. Frontal and nasal BIS values were compared in all patients. Results and Discussion: The mean BIS value from frontal versus nasal sensors was 49 ± 22 and 49 ± 21 respectively (n: 62). These values were statistically correlated (ICC 0.78, p < 0.001) indicating that nasal BIS measurement does not present a disadvantage for routine use when needed. Conclusion: Our data reveal that for measuring anesthesia depth, BIS sensor placement on the nasal dorsum shows comparable efficiency in comparison to standard frontal measurements