Comparison of ultrasound and anatomical landmark-guided technique for superior laryngeal nerve block to aid awake fibre-optic intubation: A prospective randomised clinical study

BACKGROUND AND AIMS Ultrasonography has emerged as a novel, portable, non-invasive tool encouraging airway assessment and procedural interventions. This study assesses the feasibility of ultrasound for block of internal branch of superior laryngeal nerve (ibSLN) block during upper airway anaesthesia to aid awake fibre-optic intubation. METHODS Forty American Society of Anesthesiologists' physical status I-II patients, aged 18-60 years, deemed to have a difficult airway (modified Mallampati class III-IV or inter-incisor distance <2.5 cm) and planned for awake fibre-optic intubation were randomised to either landmark group (L, n = 20) or ultrasound group (U, n = 20). All patients received nebulised 4% lignocaine (3 mL) and transtracheal injection 3 mL 2% lignocaine. Group L received landmark-guided bilateral ibSLN block with 1 mL 2% lignocaine. Group U received bilateral ibSLN block with 1 mL 2% lignocaine using a high-frequency ultrasound transducer to define the SLN space. The primary objective was assessment of quality of airway anaesthesia. Secondary objectives were time for intubation, haemodynamic parameters and patient perception of discomfort during procedure. RESULTS The quality of anaesthesia was significantly better in Group U than in Group L (P < 0.001). The mean time for intubation was shorter in Group U (71.05 ± 9.57 s) compared to Group L (109.05 ± 30.09 s, P < 0.001). Heart rate, mean arterial pressure and patient perception of discomfort were significantly increased in Group L. CONCLUSION Ultrasound for ibSLN block as a part of preparation for awake fibre-optic intubation improves quality of airway anaesthesia and patient tolerance.