Incidence, causes, and management of failed awake fibreoptic intubation—A retrospective study of 833 procedures

Awake fibreoptic intubation has been considered a gold standard in the management of the difficult airway. However, failure may cause critical situations. The aim of this study was to investigate the incidence and causes of failed awake fibreoptic intubation at a tertiary care hospital. The study was conducted at St. Olav University Hospital in Trondheim, Norway. Problems occurring during anaesthesia are routinely recorded in the electronic anaesthesia information system (Picis Clinical Solutions Inc.), including difficult intubations. We applied text search on all anaesthesia records between 2011 and 2021 and identified 833 awake fibreoptic intubations. The anaesthesia records were examined to identify failed awake fibreoptic intubations, the cause of failure and how the airway ultimately was secured. Among 233,938 patients who received anaesthesia, 90,397 received tracheal intubation and 833 received awake fibreoptic intubation. Twenty‐nine of the procedures failed. In nine patients the failure caused loss of airway control with desaturation and hypoventilation. The major causes of failure were dislodged tube after induction of general anaesthesia (n = 8), patient distress (n = 5), tube not able to pass (n = 5), and airway bleeding (n = 3). The situations were primarily solved using direct laryngoscopy, with or without bougie, or with video laryngoscopy. Tracheostomy was performed in four patients. Awake fibreoptic intubation failed in 3.5% of patients, most often due to dislocation, problems passing the tracheal tube, or patient discomfort. The failure rate was higher than in previous studies.

5][6] However, as a common first choice in an expected difficult airway the procedure may fail.[9] A recent prospective cohort study in the United Kingdom (UK) found that approximately 1% of awake fibreoptic intubations failed and that 11% of these procedures were complicated. 6Failed attempts in 2% of the procedures were reported in a large Canadian study. 4A United States closed claims analysis identified several serious complications in failed awake fibreoptic intubations. 10The NAP4-audit in the United Kingdom, on adverse events during airway management, found 91 major airway complications related to tracheal intubation among approximately 1.1 million anaesthesias. 8The audit identified 15 failed awake fibreoptic intubations. 11In a study of awake fibreoptic intubations recorded by video through an additional nasal fiberscope, the authors identified several mechanisms that prevented successful passing of the tracheal tube. 124][15][16] In recent years, the widespread use of video laryngoscopes, second-generation laryngeal masks, the possibility to reverse neuromuscular blockade with sugammadex, and the teaching of surgical techniques for emergency front-of-neck access have changed the approach to the difficult airway. 3 How these novel approaches affect the indication and the probability of success for awake fibreoptic intubation, and how the airway is secured in cases of failed awake fibreoptic intubation, are important questions.A systematic review and meta-analysis, including 12 randomized trials of airway devices during awake intubation, found awake fibreoptic intubation, video laryngoscopy, and optical stylets to have comparable results with respect to both success rate and procedural complications. 17ere are several studies that have investigated the incidence of failed awake intubation.Less is known from larger study populations about the clinical context in which the failure occurs, and how the airway is secured when fiberoptic awake intubation fails.The main aims of this study were to estimate the incidence and causes of failed awake fibreoptic intubations and to assess how these failures were ultimately handled.

| Human subjects' protection
The study was given a full formal assessment by the Regional Committee for Medical and Health Research Ethics and found to fall outside the working area of the Norwegian Health Research Act (reference number 2019/50, 01.03.2019REK-Midt).The study was given hospital approval as a quality improvement study, and the need for informed patient consent was waived according to Norwegian health care legislation.

| Study design and setting
This is a single-centre retrospective study performed at the Department of Anaesthesia and Intensive Care Medicine at the St. Olav Hospital in Trondheim, Norway.This is an 850-bed tertiary teaching hospital, covering all common surgical procedures except organ transplantation and paediatric cardiac surgery.
All anaesthetic and intensive care records at the hospital are managed in an electronic anaesthesia information system (Picis Clinical Solutions Inc.).The records included data on age, sex, ASAclassification, type of surgery, and type of airway handling as well as data on physiologic measurements of respiratory and circulatory parameters.Anaesthesia-related problems are routinely recorded in the «problem checkbox», grading problems from minor problems to death.The method for recording anaesthesia-related complications is well validated and has been used in our department for more than 30 years. 18,19The anaesthesia record also contains fields for free-text descriptions, giving the anaesthesia provider the possibility to give a more elaborate description of events.
The free text from the included records were assessed by an experienced anaesthesiologist (author KAHK).Only two more cases of awake fibreoptic intubation were identified this way, indicating that the combination of text search and manual assessment was effective.
Fibreoptic intubations performed during general anaesthesia were excluded unless the reason was a failed awake procedure.Awake intubations using direct laryngoscopy or video laryngoscopy as the primary approach were also excluded.Awake fibreoptic intubation was only performed in patients with expected difficult intubation.
The included procedures were assessed to reveal any problems during the procedure, and whether the procedure succeeded or failed (primary endpoint).We also assessed how the failed procedures were ultimately solved.Relevant clinical variables containing numeric data and free text were collected from the electronic records during the individual assessment.

| Equipment, medications, and clinical protocols
The following flexible bronchoscopes were used in the department during the study period: In most cases, the type of flexible bronchoscope applied was not documented in the anaesthesia record.The departmental procedure for topical anaesthesia recommends lidocaine spray 100 mg/mL in the oral cavity combined with topical anaesthesia of the trachea with lidocaine 40 mg/mL administered through the flexible scope.For nasal intubations, tetracaine 16 mg/mL on a nasal tampon was most often applied.The procedure recommends either midazolam and fentanyl or remifentanil and propofol separately or in combination.It also recommends awake sedation, stating: "Carefully titrated sedation.It is important to always be able to communicate with the patient."

| Study size
Patients were included between the March 1, 2011, when the electronic anaesthesia information system was fully operational, and the December 31, 2021.No formal sample size calculation was performed.Due to a lack of manpower and challenges imposed by the COVID-19 pandemic, the finalization of the manuscript was delayed.

| Statistical methods
Statistical analysis was performed with the software R version 4.0.3 with the package "ggplot2." 20Data are presented as means with standard deviation or proportions, in some instances with 95% confidence interval (95% CI), as appropriate.
Twenty-nine failed awake fibreoptic intubation were identified (3.5% of the procedures).An overview of clinical problems during these failed attempts, and how these problems ultimately were solved, is given in Table 2.A more detailed description of each failed procedure is given in Table S2.In nine patients there was loss of airway control with desaturation and hypoventilation.
A description of the patient being heavily sedated was given for six of these patients.
Three procedures failed due to airway bleeding.Eight failures were caused by dislodging of the tube after induction of general anaesthesia.In three of these instances, an adequate CO 2 -curve was recorded before induction of general anaesthesia.In another four, deep sedation was given due to coughing and other difficulties related to passing the tube.In one patient, cuff rupture was identified after intubation and dislodgement occurred when the tube was changed over a tube exchanger.Five procedures failed due to pharyngeal reflexes and/or patient discomfort, and in five procedures the tube could not be passed.In 21 of the failed awake fibreoptic intubations, the airway was secured using direct laryngoscopy (n = 8) or video laryngoscopy (n = 9) after induction of general anaesthesia, of whom six received neuromuscular blocking agents.
In four failed attempts, the airways were secured by tracheostomy or front-of-neck access, one of them emergent due to loss of control of the airway.Three tracheostomies were performed by an otolaryngologist applying local anaesthesia, with the patient awake and spontaneously breathing.The surgical access to trachea was at a level below the cricoid cartilage.The emergency tracheostomy performed by an otolaryngologist was not further described in the anaesthesia report.
Although 57% of the awake fibreoptic intubations were performed via the oral route, 72% of these failed attempts were via the oral route and 24% via the nasal route.

| DISCUSSION
The incidence of failed attempted awake fibreoptic intubation was found to be 3.5%.5][16] In nine attempted procedures the failure caused loss of airway control with desaturation and hypoventilation.The most common cause of failure was dislocation of the tube recognized after induction of general anaesthesia.Other important causes were the inability to pass the tube, pharyngeal reflexes, patient distress, and airway bleeding.
Bronchoscopy may be difficult during bleeding due to obscured view and the light-absorbing effect of blood.Two out of three patients with bleeding during awake fibreoptic intubation needed a tracheostomy to secure the airway.We also found that awake fibreoptic intubation by the oral route was associated with more failures than awake fibreoptic intubation by the nasal route.It is encouraging that 25 of the failed attempts were managed without the need of performing a front-of-neck access, the majority were managed by direct laryngoscopy or video laryngoscopy after induction of general anaesthesia.
5][6] The higher failure rate in our study is likely due to low procedural volume per anaesthesiologist, a heterogenic patient population, and that we only perform awake fibreoptic care centre demonstrated 1.3% failed awake fibreoptic intubations. 9ey experienced relatively few problems with advancing the tube, although done after the induction of general anaesthesia.Only in selected high-risk cases did they advance the tube during spontaneous ventilation, and the study was performed in a hospital where awake fibreoptic intubations were performed in 12% of all general anaesthesias.
In our study, many attempts failed due to inability to advance the tube into the trachea while the bronchoscope was in the correct position, interrupting the attempt.In a case report describing a patient with severe airway malignancy, extreme deviation, and sharp angle probably caused failure of awake fibreoptic intubation, resulting in an awake tracheostomy. 13In a study of 45 awake fibreoptic intubations recorded by video through an additional nasal fiberscope, the authors identified several mechanisms that prevented successful passing of the tracheal tube. 12The authors demonstrated that the tube frequently stopped at the right arytenoid or in the inter-arytenoid soft tissues.Moreover, the so-called "Murphy's eye" in the tracheal tube was sometimes "hooked" in the right arytenoid, in which a 90 counter-clockwise rotation of the tube often solved the problem.In our departmental procedure, rotation of the tube is recommended in these instances.
In eight instances, dislocation occurred after induction.Deep sedation and/or mechanical problems during tube advancement most likely contributed to an oesophageal dislocation in five of these.A possible mechanism may be "backward migration," that is, when advancing the tube over the fiberscope the tube may push the midsegment of the fiberscope toward the oesophageal inlet and dislocate the fiberscope. 21It is also possible for a tracheal tube positioned in the tracheal inlet to dislodge to the oesophagus during withdrawal of the bronchoscope.In the remaining three instances, tracheal position was confirmed with end-tidal CO 2 before induction of general anaesthesia.We believe it is important to verify tube position by checking that the tube and the carina are visualized at the same time in a spontaneously breathing patient before induction of general anaesthesia.
In the United States closed claims analysis and NAP4-audit, the authors emphasized the dangers of over-sedation which contributed to several serious failures. 8,10In our study, pharyngeal reflexes and patient distress caused five procedures to fail, which may have been caused by inadequate topical anaesthesia and/or too light sedation.However, we also found six failed awake fibreoptic intubations with loss of airway control where the patients were heavily sedated.How to practice the art of anaesthesia may be the issue here, that is, anesthetize well with local anaesthesia and titrate sedation to the optimal level, anaesthetize before you advance the tube or not sedate at all. 9,22The need for deep sedation may be a good reason to abandon awake fibreoptic intubation as the primary approach.A major difference between our study and NAP4 is that the latter is based on case reports, and only more serious complications are reported.Our material includes all failures-most of them leading to minimal or no patient harm.Even less harm was found in a study performed at a training course in awake fibreoptic intubation, on healthy participating anaesthetists, revealing a failure rate of 10% with mainly minor complications. 23 found a significant decrease in the incidence of awake fibreoptic intubation during the study period, reducing from 1.44% in 2011 to 0.6% in 2021, raising the question of whether there will be too few cases to get the right level of experience.There is an unsettled debate whether awake fibreoptic intubation should be a procedure all anaesthesiologists should master or a procedure that should be delegated to fewer practitioners. 3,17A recent meta-analysis T A B L E 2 An overview of clinical problems causing failure of awake fiberoptic intubation, and airway procedures applied to secure the airway.

Clinical problem
No.
How the airway was secured (no.) supported awake intubation with devices such as video laryngoscopes and fiberoptic stylets and concluded them to be clinically comparable to awake fibreoptic intubation. 17The individual doctor rarely encounters situations where the procedure fails.It is therefore important for clinicians to learn the pitfalls of fiberoptic intubation from the studies performed.

| Strengths and limitations
A strength with our study is the high number of patients receiving general anaesthesia assessed for inclusion.As awake fibreoptic intubation is a low-incident procedure, with a low failure rate, a large study population is needed to estimate the incidence of failed procedures.However, the retrospective design of the study represents a methodological weakness.In several of the incidents, the choice of tube size, type of fiberscope, timing of neuromuscular blockers, and the extent of technical and clinical problems were poorly documented.
This reflects that the study relied on the quality of the procedural documentation in routine anaesthesia.As several studies find failed awake fibreoptic intubation in approximately 1% of attempted procedures, a prospective design would require a very large sample size.In our study, the heterogeneity in patients and procedure characteristics is a strength with respect to the external validity of the findings for a mixed surgical population.

Awake fibreoptic intubation failed in 3 .
5% of attempts, most often due to dislocation of the tracheal tube, problems when trying to pass the tube, or patient discomfort.Some failures were associated with loss of airway control with desaturation and hypoventilation, in which oversedation was evident.Despite the need for front-of-neck access in some cases, most failed cases were solved by direct laryngoscopy or video laryngoscopy in general anaesthesia.As awake fibreoptic intubation is still an indispensable technique in the management of the difficult airway, lower procedural volumes and increased failure rates may be concerning.AUTHOR CONTRBUTIONSStudy design: KAHK, SEG, SF; Data collection: KAHK, SF; Data analysis and interpretation of results: KAHK, SEG, TN, SF; Manuscript draft and revision: KAHK, SEG, TN, SF.All authors have approved the final version of the manuscript.