Sternomental distance predicts vagal reflex during suspension laryngoscopy: A prospective cohort study.

OBJECTIVES: Vagal reflex (VR) during suspension laryngoscopy (SL) is a potentially life-threatening complication. However, preoperative risk stratification tools are lacking, especially for healthy adults. This study aimed to identify the anatomical and clinical predictors of intraoperative VR during SL and establish actionable thresholds for risk stratification. METHODS: This prospective observational cohort study enrolled 371 adult patients who underwent SL under general anesthesia at a tertiary academic hospital between January 2022 and December 2023. Preoperative anatomical measurements, including sternomental distance (SMD), neck circumference, and thyroid-mandibular angle (TMA), were obtained. Logistic regression, generalized additive modeling, and piecewise linear regression analyses were performed to identify independent predictors and determine the optimal threshold for VR risk. RESULTS: In this case-enriched cohort (n = 371, including 118 with and 253 without VR), SMD was significantly shorter in the VR-positive group than in the VR-negative group (17.01 ± 1.89 cm vs. 17.62 ± 1.90 cm, P = 0.004). Multivariate analysis identified shorter SMD as an independent VR predictor (adjusted OR: 0.83, 95% CI: 0.73-0.94, P = 0.0033). A threshold of 18.2 cm was identified, with reduced VR risk above this value (OR: 0.59, 95% CI: 0.39-0.89, P = 0.01). CONCLUSION: Shorter SMD was independently associated with an increased risk of intraoperative VR during SL. Preoperative SMD measurement may provide a simple, noninvasive method for identifying high-risk patients and guiding targeted perioperative strategies to enhance airway safety during microlaryngeal surgery.