To the Editor
We read with interest the editorial on “Airway management before intervention: what we know and what we do.”1
We are pleased to learn that colleagues other than us believe that it may be time to rethink the methods used for preinduction airway evaluation. We agree that it is time to include assessment of risk factors for other airway management modalities than intubation by direct laryngoscopy.
In the editorial, the authors quote our study examining the diagnostic accuracy of predicting difficult tracheal intubation and difficult mask ventilation.2 In regard to the comments in the editorial, we would like to elaborate on a few points. The Danish Anaesthesia Database only allowed us to collect and analyze data on the 2 questions regarding anticipation of difficulties with (1) facemask ventilation and (2) tracheal intubation. Although it was impossible for us to explore the methods used for the airway assessments, these were to some extent based on examination of known risk assessment tools for difficult laryngoscopy (DL). We conducted a survey on 29 Danish anesthesia departments (approximately 70% national coverage) inquiring on departmental guidelines for airway assessment. Some or all of the following risk factors for DL were listed on the 29 assessment forms: mouth opening, Mallampati score, cervical spine movement, jaw protrusion, thyromental distance, and history of a previous difficult intubation. The median number of risk factors registered was 4 (range 1–6). Thus, it would be fair to assume that the answers to anticipation of difficulties were, to some extent, based on the application of risk assessment tools. Our aim was to demonstrate the diagnostic accuracy of airway assessment in every day clinical practice, and thus we did not pursue data on individual airway assessment tools, which also were deemed infeasible.
Nevertheless, we share the authors’ advocacy for evidence on the effect of using multivariable risk tools for airway assessment. Consequently, we designed a cluster randomized trial allowing us to compare the use of the Simplified Airway Risk (SARI) with a control group continuing existing practice.3
Using the SARI was not superior to existing practice on our primary outcome, the overall incidence of unanticipated difficult intubation. We found that 89% (SARI) and 91% (control) of all difficult intubations were unanticipated (patients scheduled for advanced intubation techniques were excluded), underlining the findings of our previous work. We are currently working on an article with data on the individual risk factors from this trial. It will reflect the efficacy of assessing risk factors in nonselected patients from everyday practice in contrast to previous cohort studies describing rigorous and standardized study designs on a preselected patient population, making it difficult to extrapolate to everyday conditions.
We found the results of the survey on airway assessment forms intriguing because they underline the diversity in airway assessment and the predominant attention paid to prediction of DL. We appeal the authors to publish the results of this survey and align with them in the call for solutions for a better and evidence-based airway assessment.
Anders Kehlet Nørskov, MD, PhDDepartment of AnaesthesiologyCopenhagen University Hospital, Capital Region of DenmarkNordsjællands HospitalHillerød, DenmarkCopenhagen Trial UnitCentre for Clinical Intervention ResearchCopenhagen University Hospital, RigshospitaletCopenhagen, Denmarkanderskehlet@hotmail.com
Charlotte Vallentin Rosenstock, MD, PhDDepartment of AnaesthesiologyCopenhagen University Hospital, Capital Region of DenmarkNordsjællands HospitalHillerød, Denmark
Jørn Wetterslev, MD, PhDCopenhagen Trial UnitCentre for Clinical Intervention ResearchCopenhagen University Hospital, RigshospitaletCopenhagen, Denmark
Grethe Astrup, MDDepartment of Anaesthesiology and Intensive CareSection SouthAarhus University HospitalAarhus, Denmark
Arash Afshari, MD, PhDDepartment of Anaesthesiology, Juliane Marie CentreCopenhagen University Hospital, RigshospitaletCopenhagen, Denmark
Lars Hyldborg Lundstrøm, MD, PhDDepartment of AnaesthesiologyCopenhagen University Hospital, Capital Region of DenmarkNordsjællands HospitalHillerød, Denmark
1. Hung O, Law JA, Morris I, Murphy M. Airway assessment before intervention: what we know and what we do. Anesth Analg. 2016;122:17521754.
2. Nørskov AK, Rosenstock CV, Wetterslev J, Astrup G, Afshari A, Lundstrøm LH. Diagnostic accuracy of anaesthesiologists’ prediction of difficult airway management in daily clinical practice: a cohort study of 188 064 patients registered in the Danish Anaesthesia Database. Anaesthesia. 2015;70:272281.
3. Nørskov AK, Wetterslev J, Rosenstock CV, et al. Effects of using the simplified airway risk index vs usual airway assessment on unanticipated difficult tracheal intubation - a cluster randomized trial with 64,273 participants. Br J Anaesth. 2016;116:680689.