BACKGROUND: Betel-nut chewing (BC) causes oral submucous fibrosis (OSF), and this leads to difficult tracheal intubation (DI). Unanticipated DI was reported in chewers with apparently normal preoperative airway evaluations (PAEs). This analysis aims to investigate whether BC is an independent risk on DI besides the common DI risk prediction factors. METHODS: After the approval of Institutional Review Board and the written informed consent were obtained, 2,682 patients were enrolled in a cohort. PAEs, intubation difficulty scale (IDS), intubation time, and perceived DI were recorded prospectively. All 805 male patients received classical intubation, 307 with BC and 498 without BC were analyzed. Data were analyzed by Student's t-test and chi-square test. Stepwise logistic regression was performed to identify BC effects on IDS adjusting for related factors with WEKA (Waikato Environment for Knowledge Analysis; Machine Learning Group at the University of Waikato, Hamilton, New Zealand). RESULTS: Fewer BC patients were Cormack-Lehane (CL) grade I (38.9% vs. 47.6%) or IDS degree 〞Easy〞 (24.8% vs. 33.5%). Compared with IDS degree 〞Easy〞, patients in the BC group had a significantly higher odds ratio (OR) for 〞Slight + Moderate-Major〞 degree than in the non-BC group (adjusted OR, 1.75; 95% CI, 1.15-2.68). Compared with CL grade I, patients with BC was an independent risk for II (adjusted OR, 1.53; 95% CI, 1.02-2.32) and IV (adjusted OR, 3.25; 95% CI 1.01-10.49). Otherwise, patient's age ≥ 46 and the presence of teeth were also significant risk factors for IDS degree 〞Slight + Moderate-Major〞. CONCLUSION: BC increased not only the tracheal intubation difficulty in patients with apparent OSF but also in patients with PAEs. BC is an independent risk factor besides the commonly used DI prediction factors. We suggest physicians operating on BC patients to be better prepared for DI.
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