Evaluation of intracranial pressure by repeated ultrasonographic measurments of optic nerve sheath diamater (ONSD) during fiberoptic bronchoscopy (FOB) procedure

ABSTRACT Objective: This study aims to monitor intracranial pressure (ICP) during fiberoptic bronchoscopy (FOB) by measuring the optic nerve sheath diameter (ONSD) using ultrasonography, a method with established reliability; to identify potential increases in ICP; to emphasize the need for heightened caution during the procedure in patients at risk of morbidity and mortality due to elevated ICP; and to contribute to the existing body of literature with the findings obtained. Materials and Methods: A total of 75 patients who underwent routine bronchoscopy and endobronchial ultrasound-guided bronchoscopy (EBUS) between December 2024 and May 2025 at the Bronchoscopy Unit of Karadeniz Technical University Farabi Hospital were included after being informed and providing consent. This prospective study was completed within 6 months after obtaining ethics committee approval. ONSD values were recorded before the procedure, during the procedure, and five minutes after the procedure, along with simultaneous systolic/diastolic blood pressure and heart rate measurements. ONSD measurements were performed using an L38e/10–5 MHz variable frequency linear probe. ONSD was measured from the area between the hyperechoic dural sheaths surrounding the hypoechoic subarachnoid space around the optic nerve. For each patient, three measurements were taken 3 mm below the papilla (as the best contrast with surrounding tissues occurs at this level on USG). The average of three measurements for each eye was recorded separately. Results: A total of 75 patients (mean age 57.9±13 years; 64% male) were included in the study. At least one comorbid disease was present in 75.7% of the patients. The most common indications were malignancy (64%) and interstitial lung disease (46.7%). Bronchoscopy was performed in 56% and EBUS in 44% of the patients. The mean procedure time was 23.4±9.8 minutes. The most commonly used premedication combinations were midazolam (40%), midazolam+fentanyl (29.3%), and midazolam+fentanyl+propofol (28%). Significant changes were observed in systolic and diastolic blood pressure and heart rate during the procedure (p<0.05). ONSD values in both eyes increased significantly during the procedure and remained higher than baseline levels after the procedure (p<0.001). This increase was also statistically significant when analyzed separately in bronchoscopy and EBUS groups. Similar significance was found across different medication groups. No significant correlation was found between procedure duration and post-procedure ONSD (p>0.05). Conclusion: This study showed that fiberoptic bronchoscopy and EBUS procedures cause significant but temporary increases in intracranial pressure as evaluated by ONSD measurements. Although these increases partially regressed after the procedure, they did not return fully to baseline levels. The different sedative agents used in premedication had similar effects. These findings suggest that particular attention should be paid to patients at neurological risk during bronchoscopy with regard to potential ICP elevation. Keywords: Bronchoscopy, Endobronchial ultrasound-guided bronchoscopy, Intracranial pressure, Ultrasonography