Mismatch Between Preoperative Airway Assessment and Unanticipated Difficult Tracheal Intubation: A Retrospective Case–Control Study

Background/Objectives: Unanticipated difficult airway remains a critical patient safety concern in perioperative care. Despite routine preoperative assessment, difficult intubation may still occur in patients without obvious high-risk findings. This study aimed to evaluate perioperative factors associated with unanticipated difficult intubation and to examine the relationship between preoperative assessment and intraoperative intubation difficulty in routine clinical practice. Methods: This retrospective case–control study included adult patients undergoing general anesthesia with tracheal intubation between 2015 and 2020 at a tertiary care hospital. Unanticipated difficult intubation was defined as requiring ≥3 intubation attempts without documented preoperative suspicion of difficult airway. Patients with anticipated difficult airway or preoperative mechanical ventilation were excluded. A total of 95 cases and 429 controls were analyzed. Associations were explored using multivariable logistic regression. Results: Among 524 patients, cases more frequently had ASA physical status III and airway/neck/oral deformity. Notably, intubation difficulty became evident only at laryngoscopy, characterized by poorer visualization, increased intubation attempts (median 4 vs. 1), and frequent escalation to video laryngoscopy. Severe laryngoscopic views (Cormack–Lehane grade III–IV: 74.8% vs. 3.0%) were markedly overrepresented among cases. In multivariable analysis, ASA III and airway deformity remained independently associated with unanticipated difficult intubation. The model demonstrated modest discrimination (AUC 0.685). Conclusions: Unanticipated difficult intubation was uncommon but clinically important and frequently became apparent only during airway management. Although several associated factors were identified, routine bedside airway assessment alone may not reliably predict all cases of intraoperative difficult intubation. These findings highlight the limitations of routine bedside airway assessment in identifying all patients who subsequently experience difficult intubation and support the need for improved strategies to identify patients at risk.