First step to safe anesthesia: Pre-operative prediction of difficult airway.

Corresponding author: Kye-Min Kim, M.D., Ph.D., Department of Anesthesia and Pain Medicine, Inje University College of Medicine, Sanggye Paik Hospital, 761-1, Sanggye 7-dong, Nowon-gu, Seoul 139-707, Korea. Tel: 82-2-950-1173, Fax: 82-2-950-1323, E-mail: kyemin@paik.ac. kr Copyright c Korean Society of Anesthesiologists, 2009 cc This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Difficult airway is a major factor threatening the safety of anesthesia. According to the database of the American society of Anesthesiologists Closed Claims Project [1], difficult tracheal intubation is the second most common cause of adverse events bringing about anesthesia-related malpractice claims. To avoid the unanticipated difficult intubation and the catastrophic outcomes, preoperative airway assessment and recognition of difficult intubation are necessary. Several factors such as Mallampati classification, thyromental distance, sternomental distance have been related to difficult intubation [2]. Predictive abilities for difficult intubation of these factors or composite indexes have been tested [2,3]. Postburn sternomental contractures with limited head and neck mobility are considered to increase the incidence of difficult airway. A recent case report on a child with an advanced neck contracture after burn shows us how serious it can be [4]. Therefore, very careful approach to the airway management is required in these patients. In this issue of Korean Journal of Anesthesiology, Jeong et al. [5] compared the predictive abilities for difficult intubation in those patients among three tests: modified Mallampati classification, modified Onah’s classification, El-Ganzouri and Colleagues Multivariate Risk Index (EGRI) [6]. In the study, Jeong et al. introduced Onah’s classification [7] which is originally for guiding surgical options. They modified it by removing elements of surgical consideration and used the simplified form for predicting difficult intubation. In their study, sensitivity and specificity of Mallampati classification for predicting difficult intubation were 97.7% and 19.7%, respectively. On the other hand, sensitivity and specificity of modified Onah’s classification were 86.0% and 84.9%, respectively, which are remarkably improved. Even though the diagnostic performance of EGRI were slightly lower than those of modified Onah’s, they seem to be acceptable also (sensitivity and specificity of EGRI were 83.7% and 75.8%, respectively). On the basis of these results, modified Onah’s classification was more accurate test for difficult intubation than the others in patients with sternomental contractures (Accuracy of modified Onah’s classification, EGRI and modified Mallampati classification were 85.3%, 78.9% and 50.5%, respectively). For safety issue, we must reduce the incidence of unanticipated difficult intubation as far as we can. To do so, we need to use more accurate test for the prediction of difficult intubation in case of postburn sternomental contractures. From this point of view, Jeong et al.’s study has clinical implication. However, we should also keep in mind that there is some probability of false negative prediction even with the most accurate test. So, it is recommended to be careful in the airway management regardless of the results of predictive tests. Furthermore, we should be fully aware of ‘practice Guidelines for Management of the Difficult Airway’ [8] and be familiar with several alternative techniques to laryngoscopic intubation.