Study of Changes in Optic Nerve Sheath Diameter Following Tracheal Intubation Using Macintosh Laryngoscope or Fibreoptic-Guided Intubation Through Ambu Aura-I: A Randomised Controlled Study

Background: Neuroanaesthesiologists are faced with managing and optimising the intracranial pressure in the perioperative period. Laryngoscopy and tracheal intubation are known to increase sympathetic activity that is well tolerated by healthy patients but may be detrimental to many comorbid patients. We, therefore, hypothesised that airway management and tracheal intubation through Ambu Aura-I (Ambu, Baltorpbakken 13, Denmark) may be associated with lesser changes in optic nerve sheath diameter (ONSD) compared to conventional tracheal intubation and designed a study to ultrasonographically measure the changes in optic nerve sheath diameter following tracheal intubation using Macintosh laryngoscope or fibreoptic-guided intubation through Ambu Aura-I in patients receiving endotracheal anaesthesia. Material and methods: This randomised controlled hospital-based clinical study was conducted on 60 patients divided into two groups: group 1 (n=30, tracheal intubation facilitated by direct laryngoscopy with Macintosh laryngoscope) or group 2 (n=30, fibreoptic-guided tracheal intubation through Ambu Aura-I), undergoing elective surgery under general anaesthesia requiring tracheal intubation. Results: Baseline parameters before induction of anaesthesia were recorded for further comparison. Baseline ONSD at 3 mm behind the globe in both eyes (before induction of anaesthesia), both in transverse and the coronal plane, was measured by transorbital sonography with the patient lying in the supine position using a portable Sonosite Turbo-M ultrasonography (Fujifilm Sonosite, Bothell, USA) machine. End-tidal carbon dioxide concentration (EtCO(2)) was also recorded at this time. Observations of HR, systolic blood pressure (SBP), diastolic blood pressure (DBP), mean blood pressure (MBP), oxygen saturation (SpO(2)), EtCO(2), and ONSD measurements were recorded immediately and at three and five minutes after intubation, and complications were recorded. Data collected were tabulated, and statistical analysis was done using SPSS 22.00 for windows (SPSS Inc, Chicago, USA). The ONSD increase peaked at 4.19±0.35 and 4.16±0.31 mm in right and left eyes. Like in group 1, the ONSD decreased slightly to 4.06±0,29 and 4.05±0.29 mm in right and left eyes in group 2 at 10 minutes after intubation. The changes in ONSD when compared to baseline values (before intubation) were statistically not significant (p>0.05). Between-group comparison in ONSD in both the eyes at different time intervals was statistically not significant (p>0.05). Conclusion: We conclude that fibreoptic-guided tracheal intubation through Ambu Aura-I is not superior to tracheal intubation using direct laryngoscopy with Macintosh laryngoscope in terms of its effect on intracranial pressure, as measured ultrasonographically by optic nerve sheath diameter.