Jaspreet Kaur and Chris Frerk highlight why videolaryngoscopy is an appropriate technique to have available when planning airway management strategies
We performed a retrospective analysis of difficult laryngoscopy and failed intubation cases over an eight-month period at a large district general hospital where videolaryngoscopy is freely available and widely used. There were 10,627 general anaesthetics performed during the study period and in 100 cases laryngoscopy was difficult. The primary intubation plan and the use of rescue techniques were reviewed for each case with difficult laryngoscopy. Videolaryngoscopy was used successfully as a rescue technique in 70% of cases where intubation had failed using direct laryngoscopy. Wake up and postponement of surgery was used as a rescue technique in 15% of cases of failed direct laryngoscopy. When planning airway management strategies, videolaryngoscopy is an appropriate technique to have available.
Background
Securing the airway with a tracheal tube has been conferred with great importance during emergency and elective anaesthesia. Any method which can improve our ability to secure the airway in a timely manner should therefore be investigated.
The Difficult Airway Society published guidelines for the management of unanticipated difficult intubation in 2004 [1], recommending a stepwise approach, ensuring oxygenation and limiting airway instrumentation. Direct laryngoscopy was recommended for Plan A (the initial tracheal intubation plan) with a maximum of four attempts at intubation. A poor view at direct laryngoscopy is recognised as a major cause of difficult intubation and Plan A then supports the use of a bougie or an alternate laryngoscope. Plan B in the 2004 guidelines (the secondary tracheal intubation plan) is one attempt at intubation through a laryngeal mask airway. If tracheal intubation fails with Plan A and B but oxygenation remains possible, then waking the patient up and postponing surgery is recommended (Plan C).
Since the guidelines were published, a variety of new laryngoscopic equipment has become available to try and alleviate the challenges posed by difficult direct laryngoscopy.
Videolaryngoscopy was introduced at our hospital at the end of 2007. Four years later at the time of this study there were four devices available: McGrath series 5, Pentax AWS, Glidescope and Airtraq. Videolaryngoscopy is widely used at our hospital with a collective experience of over 1000 video-intubations. Most consultants are familiar with videolaryngoscopy and over a quarter of consultants are very experienced with the technique (Table 1).
Table1. Consultant_experience_with_videolaryngoscopy
In their review of non-standard laryngoscopes and rigid fibreoptic intubation aids, Mihai et al. [2] highlighted the need to study large numbers of unselected patients to obtain information about genuinely difficult cases rather than extrapolating data obtained from cohorts of patients who are predicted to be difficult, or from those whose tracheas can be easily intubated despite a poor view at laryngoscopy.
We performed a retrospective case analysis of 100 consecutive cases of difficult laryngoscopy and failed intubation to identify how often videolaryngoscopy or wake up was used to rescue failed intubation associated with difficult direct laryngoscopy. Unlike closed claims studies [3] and NAP4 [4], we did not limit our study to cases with poor outcomes but reviewed all cases of difficult direct laryngoscopy regardless of outcome.
Methods
We identified all patients with a difficult laryngoscopy (Cormack- Lehane [CL] grade 3 or 4 laryngoscopy view [5]) from our departmental audit database over an eight-month period (from December 2011 to July 2012 inclusive). All critical incidents over this period were also reviewed to identify any additional patients where airway management had been challenging to the anaesthetists involved. This study has our Trust’s Caldicott Guardian’s approval for publication.
The case notes of each patient were reviewed, and qualitatively analysed for aspects of airway management including initial laryngoscope used, number of intubation attempts, best view obtained and rescue plans used – including use of alternative laryngoscopes, use of a supraglottic airway device, wake up and postponement of surgery, or front of neck airway access. The grade of the most senior anaesthetist present during induction of anaesthesia and, where appropriate, the grade of any help called were also noted, along with any complications recorded such as hypoxia or airway trauma.
Our primary outcome measure was use of a videolaryngoscope to intubate the trachea following failed intubation in patients with a CL grade 3 or 4 direct laryngoscopic view. Our secondary outcome measure was failed intubation with wake up and postponement of surgery.
Results
There were 10,627 general anaesthetics performed during the eight-month study period. In 2834 (27%) cases the airway was managed with tracheal intubation, in 7793 (73%) the airway was managed with a supraglottic airway device or facemask.
One hundred difficult direct laryngoscopies (CL grade 3 or 4 view) were identified from our audit database. An overview of the management of these 100 cases is shown in Figure 1.
Figure 1. Management_of_100_difficult_laryngoscopy_airway_cases
On reviewing the original anaesthetic records, external laryngeal manipulation improved the view in six cases to a CL grade 2 and the trachea could be intubated without difficulty over a gum elastic bougie. These cases were excluded from further analysis.
Of the 94 remaining cases, 12 had awake fibreoptic intubation performed because of anticipated airway difficulty, with difficult direct laryngoscopy confirmed after induction of anaesthesia. These 12 cases were also excluded from further analysis.
Therefore, 82 cases of difficult laryngoscopy (2.9% of all intubated cases) occurred during the study period and were analysed in detail. These are described below by primary intubation plan and by rescue technique used.
Primary tracheal intubation plan
Macintosh laryngoscopy
Direct laryngoscopy with a Macintosh blade was the primary plan in 69 cases, 41 of which were intubated blind without a change in laryngoscope type. In 28 patients, tracheal intubation failed using the Macintosh blade and a variety of rescue strategies were adopted. A McCoy blade was used successfully in eight cases and failed in four. Videolaryngoscopy was used successfully for rescue in 14 cases and failed in two. Asleep fibreoptic guided intubation was used successfully in two cases. In three cases intubation attempts were abandoned and the patient was woken up. In the final case, blind tracheal intubation using a Macintosh laryngoscope was eventually achieved following a failed rescue attempt with a videolaryngoscope. No surgical airways were required.
McCoy laryngoscopy
Direct laryngoscopy with a McCoy blade was the primary plan in four cases, all of which were successfully intubated blind.
Videolaryngoscopy
The Glidescope videolaryngoscope was used successfully as Plan A in one patient. Post-intubation direct laryngoscopy with a Macintosh laryngoscope gave a CL grade 3 view.
The McGrath Series 5 videolaryngoscope was used successfully as Plan A in one patient. Post-intubation direct laryngoscopy with a Macintosh laryngoscope gave a CL grade 3 view.
The Pentax AWS videolaryngoscope was chosen as Plan A in one case. In this case tracheal intubation failed because of reflections from copious secretions and was subsequently achieved blind using a Macintosh laryngoscope and bougie.
Asleep fibreoptic laryngoscopy
Asleep fibreoptic intubation had been chosen as Plan A for two patients. The first was a middle-aged adult with severe learning difficulties and micrognathia but the larynx could not be identified using this technique; however, Plan B (tracheal intubation with a Glidescope) was successful. In the second case, the night registrar assessed and consented an adult patient with a dental abscess for awake fibreoptic intubation. The following morning the consultant on call changed the plan to asleep fibreoptic intubation but was unable to locate the trachea and woke the patient up. An uneventful awake fibreoptic intubation was performed later that day.
Other
There were four cases where the primary plan had been to use a supraglottic airway device but conversion to tracheal intubation was required. All four were intubated blind using a Macintosh laryngoscope and bougie.
videolaryngoscopy
Rescue strategies
Videolaryngoscopy as rescue after failed intubation
Videolaryngoscopy was used in 17 cases and was successful in 15 (Table 2). Videolaryngoscope rescue failed in two cases. In the first case a large soft tissue mass at the back of the tongue obscured the view of the larynx. The trachea was intubated over a gum elastic bougie placed blindly by an ENT surgeon using a Macintosh laryngoscope. In the second case, after a failed attempt at tracheal intubation with CL grade 3 view with a Macintosh laryngoscope, the anaesthetist was able to see the glottis with an Airtraq but was unable to pass a tube. A McCoy blade gave a grade 2b view [6] and tracheal intubation was accomplished using a gum elastic bougie.
Wake up as rescue after failed intubation
In four cases, intubation attempts were abandoned and the patient was woken up (0.14% of all intubations).
Case 1: A planned asleep fibreoptic intubation in a patient with a dental abscess and limited mouth opening failed. Spontaneous ventilation had been maintained using sevoflurane in oxygen and, after declaring the failed intubation, the anaesthetist woke the patient up. An uneventful awake fibreoptic intubation was performed later the same day.
Case 2: Tracheal intubation failed during a rapid sequence induction for a Nissan’s fundoplication. Initial laryngoscopy by a trainee with a Macintosh 3 blade achieved a CL 3 view; the supervising consultant took over and achieved the same view with the same blade, and then the same view with a size 4 Macintosh blade. Rescue ventilation was difficult but improved on insertion of an I-gel. The patient was woken up, their operation was postponed and they subsequently had an uneventful awake fibreoptic intubation for their surgery three weeks later.
Case 3: A patient for vocal cord biopsy had a history of previous uneventful anaesthetics and no difficulty was anticipated. Following induction of anaesthesia laryngoscopy with a Macintosh blade gave a CL grade 3 view. The consultant anaesthetist was unable to intubate using a gum elastic bougie and noted some bleeding. Further attempts at tracheal intubation were abandoned and he woke the patient up. The patient remained stable in the recovery area for a few hours following which the same anaesthetist performed an uneventful awake fibreoptic intubation; surgery and tracheal extubation were uneventful.
Case 4: A patient with no predictive factors for difficult intubation had a rapid sequence induction of anaesthesia for a diagnostic laparoscopy out of hours. The best view the trainee anaesthetist could achieve using a size 3 Macintosh blade was CL grade 3, and he was unable to pass a bougie into the trachea. There was no improvement in view using a size 4 Macintosh blade. Senior help was not immediately available so no further attempts were made at intubation and the trainee woke the patient up. The operation was rescheduled for the following day and the airway was secured using an awake fibreoptic intubation.
In all cases of videoscope rescue and in three of the four cases where the patient was woken up, a consultant was either already present or arrived to assist in response to a call for help. Documented complications included bleeding in one case, desaturation in two cases and oesophageal intubation in two cases. None of the patients suffered harm from these events.
Table 2. Sequence of devices used where videolaryngoscopy was successfully used to rescue tracheal intubation
Discussion
This study details 82 cases of difficult intubation identified from 10,627 consecutive general anaesthetics at a large district general hospital. It demonstrates how unselected anaesthetists applied their knowledge, training and available equipment to deal with difficult intubations encountered in routine practice.
Our audit database is subject to rigorous quality control so we are confident that we have captured all CL grade 3 and 4 direct laryngoscopies from our operating theatres. The database does not collect cases from the Emergency Department or the Intensive Care Unit (where it is known from NAP4 [7] that airway difficulty is encountered more commonly) so we are unable to comment on rescue techniques used in these clinical areas.
Tracheal intubation that succeeds despite failed visualisation has been described as a near miss [8]. Blind tracheal intubation can evidently be an effective technique but risks soft tissue trauma and, in this series, failed in 25% of cases.
Improvement in view is well described with videolaryngoscopes [9]; however, our study has also confirmed ease of tracheal intubation using videolaryngoscopy in the majority of cases when the technique is widely available and frequently practised.
The 15 cases that were rescued using videolaryngoscopy were intubated under vision within four attempts (in accordance with Difficult Airway Society guidelines [1]). Before the introduction of videolaryngoscopy this would not have been possible and the options would have been to intubate blind, use an asleep fibreoptic technique, wake the patient up or to continue anaesthesia using a supraglottic airway device for airway maintenance.
Abandoning intubation attempts, waking the patient up and postponing surgery is an appropriate rescue technique for failed intubation and while this does not equate with harm it is an undesirable outcome. Videolaryngoscopy was not attempted in the four cases where wake up was used as rescue and it is possible that if an anaesthetist trained in videolaryngoscopy had been managing these cases (and a videoscope had been available) then tracheal intubation under vision may have been possible and wake up would not have been necessary. All four cases were subsequently managed using an awake fibreoptic intubation technique, which has been described as the gold standard for managing the anticipated difficult airway. Occasionally this remains the only likely successful approach and it is an entirely appropriate technique especially when there is known difficulty with facemask ventilation.
Any tracheal intubation may prove unexpectedly difficult or fail; NAP4 recommends that plans for difficult or failed intubation should be made before induction of anaesthesia and should include the use of alternative devices both for laryngoscopy and for airway rescue [10].
Waking a patient up and postponing surgery is a safe option but having a comprehensive strategy with appropriate equipment available is the key to safe airway management. Cooper has stated: “We should not reserve the best methods for only our most difficult patients; they should be offered to all our patients. This will provide our patients with the best care” [8].
This study demonstrates that where the technique is routinely practiced, videolaryngoscopy can be used to rescue failed tracheal intubation in the majority of cases when the larynx cannot be seen under direct vision.
Acknowledgements
The authors wish to thank Liz Gill for providing assistance with access to and interpretation of the anaesthetic audit database.
Competing interests
The authors have declared no competing interests and that no external funding was used for this study
References
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