Comparison between ultrasound-guided and anatomical landmark-guided block of internal branch of the superior laryngeal nerve for awake fiber-optic intubation in suspected difficult intubation: a randomized controlled study

Background: Airway anesthesia is pivotal for successful awake intubation provided either topically or by nerve blocks. The widespread use of ultrasonography allows anesthesiologists to evaluate complex and varied anatomy before needle insertion. This study aims to evaluate the effect of ultrasound-guided technique for the block of the internal branch of the superior laryngeal nerve in difficult airway patients in comparison to blind anatomical technique. Sixty patients aged 18-60 years, of either sex, with the American Society of Anesthesiologists' physical status (ASA) I-II were divided into two groups 30 patients of each. Group (L): using anatomical landmark technique to bilateral block internal branch of the superior laryngeal nerve (ibSLN) with 1 mL 2% Lidocaine and group (U): using ultrasound technique to bilateral block the ibSLN with 1 mL 2% Lidocaine. Assessment of the excellence of airway anesthesia during intubation by using the 5 points grading scale, time for intubation, effects on hemodynamic variables, and evaluation of patient awareness of pain and discomfort during fiber-optic intubation using numerical rating scale were compared. Results: The duration of tracheal intubation was shorter in the ultrasound group as compared to the anatomical group; also, patient comfort was significantly better in the ultrasound group besides the effect of tracheal intubation on hemodynamics which was significant with a higher peak value during intubation and post-intubation in the anatomical group compared to the ultrasound group. Conclusions: This study concludes that an ultrasound-guided block of ibSLN used as a part of the preparation of the airway for awake fiber-optic intubation enhances the quality of airway anesthesia and patient tolerance during the procedure.