Prediction of Difficult Endotracheal Intubation in Thyroid Surgery

Abstract

Background: Thyroid surgery is usually considered as difficult airway and a risk factor for intubation. Methods: All adult patients who were undergoing thyroid surgery under general anaesthesia were prospectively included in this study over a period of eighteen months to determine the incidence of difficult intubation using the intubation difficulty scale (IDS) and to assess whether features related to goitre were associated with increased risk of difficult intubation. Depending upon the IDS score calculated, two groups were formed as Group 1→IDS < 5, Group 2 → IDS > 5. The association between different variables and difficult intubation was evaluated using the chi-square test for qualitative data and the Student's t test for quantitative data. Results: The numbers of patients in Group 1 were 156 and those in Group 2 were 31. The incidence of difficult intubation was 16.5%. The highest IDS value attained was 11. Mallampati classification III or IV, thyromental distance < 65 mm. Interincisor gap < 35 mm, neck mobility < 80^o and prognathic or retrognathic mandible were statistically significant risk factors for difficult intubation. Malignant goitre was found to be associated with difficulty in intubation. Conclusions: Except for malignant goitre no other goitre related specific risk factors were associated with increased incidence of difficult intubation. The classical risk factors for difficult intubation such as Mallampati grade III or IV, interincisor gap less than 35 mm, thyromental distance less than 65 mm, neck mobility less than 80^o and mandibular abnormality were reliable predictors.