Intra-operative difficult airway identification and critical airway communication

Editor, It is the anaesthetist's professional duty to report difficult airway events that might have a significant impact on a patient's subsequent anaesthetics. As such, national bodies such as the American Society of Anesthesiologists (ASA), Difficult Airway Society (DAS) and the Canadian Airway Focus Group (CAFG) have issued recommendations on counselling of patients post DA management to allow for planning of future anaesthesia.1–3 However, the perception of a difficult airway can be highly subjective, with anaesthetists having different thresholds for what ‘difficult’ truly means. Addressing this mismatch is important to encourage the widespread reporting and dissemination of critical airway information. Few studies have examined whether anaesthetists tend to record a patient's airway as ‘difficult’ when one or more of the published definitions of difficulty has been encountered, or equally, whether they have communicated this information to the patient postoperatively. We carried out a retrospective review to study how anaesthetists identify an intra-operative difficult airway, as well as compliance with international guidelines on critical airway communication. National Healthcare Group Domain-Specific Review Board exemption was obtained for this study. We reviewed the electronic anaesthetic records of all patients who received a general anaesthetic in our tertiary institution (Tan Tock Seng Hospital, Singapore) from July to December 2014. A standard definition of the difficult airway cannot be identified in the available literature. For this review, we adapted our definitions from the ASA1 and CAFG3 guidelines. We reviewed each anaesthetic record individually by hand for the documented intra-operative airway information. For the study purposes, a case was labelled as a ‘Difficult airway’ if any of the foregoing definitions of difficulty were met. Then, for those cases, we determined whether the attending anaesthetist also subjectively recorded airway management as ‘difficult’, by placing free text comments such as ‘difficult intubation’, ‘difficult airway’ and so on in the anaesthetic record. The latter was recorded as ‘Perceived difficult airway’. For all the patients labelled as having a difficult airway in our review, we searched for documentation of follow-up counselling in the medical record, wherein the patient received information about the difficult airway during a postoperative visit by the anaesthetist, either verbally or by providing a written letter. Our primary outcomes are firstly, the proportion of ‘perceived difficult airway’ out of all difficult airway cases identified in this review and secondly, the incidence of postoperative counselling after difficult airway management in this subset of patients. Secondary outcome measured was incidence of difficult airway in our institution. Data were subjected to statistical analysis with Microsoft Excel spreadsheet and STAT v.13.0 software (Stata Corp. College Station, Texas, USA). Out of 6318 general anaesthetics performed over the review period, 198 cases were identified to have a difficult airway, with an overall incidence of 3.13%. The types of difficulty encountered appear in Table 1. Of the 198 cases of difficult airway, 87 (44%) were also ‘perceived’ as difficult by the anaesthetist, based on the presence of additional free-text recording (Table 2). The remaining 56% of difficult airway cases were identified on the basis of the definitions provided by the international guidelines. Of the 87 ‘Perceived difficult airway’ cases (Table 3), none of the cases with difficult facemask ventilation had documented follow-up after surgery. Verbal information was provided to one case (3.3%) of difficult laryngoscopy, 11 cases (26.8%) of difficult intubation and two cases (66.6%) of failed intubation. A difficult airway letter was given to only three patients (3.4%), one case of difficult laryngoscopy, one difficult intubation and one difficult/failed supraglottic device (SGD) insertion.Table 1: Incidence of difficult airway and specific types of difficulty encounteredTable 2: Proportion of ‘Perceived difficult airway’ by the attending anaesthetistTable 3: Summary of follow-up plan of the 87 cases of ‘perceived difficult airway’Despite the launch of the 2013 ASA and CAFG guidelines,1,3 our study suggested that identifying an intra-operative difficult airway was still very much a subjective decision. Possible reasons include lack of awareness and uncertainty about the guidelines. It is still controversial if difficult laryngoscopy is synonymous with difficult intubation. It is also uncertain if difficult facemask ventilation and difficult/failed SGD insertion should be viewed with the same level of caution as difficult intubation, as reasons for failure are usually multifactorial and may not equate to difficult intubation. Concerns have been raised if lowering our threshold would lead to over reporting of difficult airway, resulting in unnecessary work and stress to the patient. We wish to emphasise the importance in realising that the final goal of airway management is not intubation, but the maintenance of oxygenation and rapid recovery from hypoxaemia.4 As such, we believe that the success of facemask ventilation and SGD insertion are as critical as tracheal intubation in achieving oxygenation in an anaesthetised patient. Difficulty or failure of the above are significant threats that should be recognised and reported accordingly. Dissemination of critical airway information is vital to prevent an unexpected and unprepared airway crisis from happening to the same patient again.1–3 Our study showed poor compliance with these recommendations, possibly due to lack of awareness and resources to provide proper airway communication. A written letter is more effective than verbal communication of the difficult airway.5 With the absence of a workflow guiding postoperative communication, only three cases (3.4%) were given a written letter, while 14 (16%) cases received verbal information about their airway concerns. Recognition of a difficult airway and postop care are interlinked. The use of the ASA/CAFG classification of difficult airway ensures a more objective and accurate documentation of intra-operative airway difficulties, as opposed to relying on the subjective perception of the attending anaesthetist. On a departmental level, the airway lead anaesthetist6 could facilitate the development of a standardised workflow for proper documentation and postoperative dissemination of written critical airway information. Our study showed that usage of the 2013 ASA/CAFG difficult airway definitions was low, and often, anaesthetists failed to perceive the intra-operative airway difficulties even when the objective definitions were fulfilled. There was a low follow-up rate of patients with documented difficult airway. It would be helpful if international societies could provide a global consensus on standardising airway definitions, and if all categories of difficult airway should be reported with equal importance. We hope that the results of our study will stimulate reflection of current practice for the improvement thereof. Acknowledgements relating to this article Assistance with the study: we would like to thank J. Adam Law for his assistance with the manuscript preparation. Financial support and sponsorship: this work was supported by the Department of Anaesthesiology, Intensive Care and Pain Medicine, Tan Tock Seng Hospital, Singapore. Conflicts of interest: none.

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