Preoperative Predictors for Unanticipated Difficult Tracheal Intubation in Elective Surgical Patients

This multicenter prospective study was conducted as a survey study to evaluate certain constitutional and airway assessment parameters as predictors for unanticipated difficult tracheal intubation (DTI) in adult patients assigned for elective surgeries. Patients Methods: The study included 778 patients; 500 males and 278females with mean age of 50±14.1 years. Enrolled patients were assessed for age, gender, body weight (Wt), body height (Ht) and calculation of body mass index (BMI), cervical morphology; short thick neck and tooth morphology. Airway assessment included mouth opening assessed by measuring the inter-incisor gap (IG), the thyromental distance (TMD), the maximum range of head and neck movement and the oropharyngeal view was assessed using a modified Mallampati classification. Glottic visualization was assessed using a modified Cormack Lehane grading that was considered as the dependent parameter for which all other evaluated parameters were analyzed as independent predictors. Difficult laryngoscopy was set at Cormack Lehane Grades 3 and/or 4. Results: Cormack Lehane grading for glottic visualization defined 582, 125, 56 and 15 patients of grades I, II, III and IV, respectively and 27 patients (3.5%) had difficult intubation, 12 were grade IV, 13 were grade III and 2 patients were grade II. Cormack Lehane grading and subsequent DTI showed a positive significant correlation with BMI, presence of short neck, presence of abnormal anterior teeth and Mallampati scoring, while showed negative significant correlation with TMD and angle of head movement. Logestic regression analysis defined the presence of abnormal anterior teeth, Mallampati scoring, TMD, presence of short neck and the angle of head movement, while excluded the other parameters as predictors for DTI. ROC curve analysis defined the presence of short neck and body weight as sensitive predictors, while BMI, TMD and Mallampati scoring as specific predictors for DTI. Conclusion: No single parameter could be used as a predictor for unanticipated DTI of patients assigned for elective surgery, but the combination of detecting high BMI, short TMD, abnormal anterior teeth and high Mallampati grade, in varied combinations could predict DTI with high sensitivity and specificity.