Ultrasonographic evaluation of the effects of direct laringoscopy surgery on optical nerve diameter

Direct laryngoscopy (DL) is the most frequently performed procedure to visualize, diagnose and to treat the pathologies of the larynx. The most preferred position for direct laryngoscopy is the sniffing position. This position can affect intracranial pressure(ICP). Increase in ICP could lead to secondary insults to central nervous system. In this study, our aim was to evaluate the effect of the procedure on the ratio of optic nerve sheath diameter (ONSD) and optic nerve sheath diameter/eyeball transverse diameter (ONSD/ETD) at different time intervals in patients who underwent direct laryngoscopy. After obtaining ethical committee approval, 59 patients aged between 18-80 years, ASA 1-3 class, who underwent DL between October 2019 and March 2021 were included in the study. Ultrasonographic ONSD/ETD measurements and hemodynamic parameters of the patients were recorded at certain time intervals. These time periods are; T0; immediately after induction, T1; 10 minutes after intubation, T2; 10 minutes after insertion of the direct laryngoscope, T3; 10 minutes after the direct laryngoscope is removed and the patient is placed in the supine position. There was a statistically significant change in the ONSD levels over time (p<0.001), the situation that caused the difference was to be the higher ONSD levels at T1, T2 and T3 periods compared to baseline (p=0.003; p<0.001 and p=0.024). There was no statistically significant difference in terms of ETD levels between the follow-up times (p=0.263). There was also a statistically significant change (p=0.003) in the ONSD/ETD levels over time, the situation causing the difference was to be the higher ONSD/ETD levels in T1 and T2 periods compared to baseline (p=0,010 and p=0.005). There was no statistically significant correlation with age, body mass index, total length of the procedure and the time between intubation and mouth opening (p> 0.0083).As a conclusion, we believe that during direct laryngoscopy especially performed for laser treatment sonographic measurement of ONSD and ONSD/ETD ratios could be used as a noninvasive indicator of elevated ICP especially in patients at risk for intracranial hypertension.