Effect of superior laryngeal nerve block in alleviating sore throat after application of i-gel supraglottic airway: a randomized controlled trial

BACKGROUND: Postoperative sore throat (POST) is a common complaint after supraglottic airway device (SAD) application. Internal branch of the superior laryngeal nerve (iSLN) block has the potential to alleviate POST. The aim of this trial was to explore the effect of iSLN block in alleviating sore throat, as well as to identify the potential risk factors for POST after SAD insertion. METHODS: One hundred thirty-four patients scheduled for elective gynecological surgery were randomized to either group T: tetracaine syrup (1%) for local lubrication on i-gel supraglottic device (n = 67) or group B: i-gel insertion with water based lubricant on it and followed by bilateral iSLN block (ropivacaine, 0.375%, 2 ml for each side) (n = 67). Under ultrasound guidance, iSLN was exposed below thyrohyoid membrane. The primary outcome was the intensity of sore throat at 6 h after surgery. In addition, POST score at 0.5 h and 24 h, the severity of postoperative swallowing discomfort, acoustic analysis and complications were measured. RESULTS: Compared with tetracaine syrup for local lubrication, iSLN block resulted in a reduced intensity of POST at 0.5 h (P = 0.044, OR = 1.99, 95%CI 1.02 to 3.88) and 6 h (P < 0.001, OR = 5.07, 95%CI 2.53 to 10.14) after surgery, as well as less severity of swallowing discomfort (P < 0.001, OR = 2.21, 95%CI 1.63 to 2.99) and cough (P = 0.039, OR = 1.97, 95%CI 1.04 to 3.73). The patients after iSLN block presented lower jitter and shimmer value in acoustic analysis at 6 h after surgery (P < 0.001). CONCLUSIONS: iSLN block was effective in alleviating POST, improving voice function, as well as reducing postoperative swallowing discomfort and coughing. TRIAL REGISTRATION: Chinese Clinical Trial Registry (ChiCTR2000037974) on 8th Sept 2020. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s12871-023-02287-7.