Comparison of landmark-guided and ultrasound-guided technique for superior laryngeal nerve block to aid fibreoptic intubation - An observational study

Background and Aims: Awake fibreoptic intubation (AFOI) is the gold standard in the management of the difficult airway. Several methods to achieve airway anesthesia to aid AFOI include superior laryngeal nerve block (SLNB). This study aimed to compare land-mark-guided and ultrasound-guided techniques for SLNB to aid AFOI. Material and Methods: This was a prospective, observational study. Patients in both groups received 1 mg Midazolam and 50 μg of fentanyl for mild sedation before intubation, nasal passages were anaesthetized using lignocaine-coated nasopharyngeal airways, nebulization of 3 ml of 2% lignocaine, and intratracheal injection of 2 ml of 2% lignocaine given through cricothyroid membrane. Patients in Group L received SNLB, at the lateral end of the thyrohyoid membrane (2 ml of 1.5% lignocaine). Patients in Group U had their thyrohyoid membrane visualized using linear ultrasound probe (8 - 13 Hz) and the injection was placed just superficial to the membrane using out of plane method. The groups were compared with respect to quality of anesthesia (assessed on a 5-point scale), patient comfort during AFOI, time taken to intubation and Haemodynamics. Results: A total of 25 patients were enrolled: 13 in Group L and 12 patients in Group U. The demographics were comparable. Quality of airway anesthesia, time taken to intubation, haemodynamics and patient comfort were comparable. All were intubated successfully and there were no complications. Conclusion: USG-guided SLNB was comparable to landmark-based method with respect to quality of airway anesthesia and patient comfort. USG-guided block did not add any advantage over the landmark-based method.