8. Failed Intubation Flashcards
Incidence
Failed intubations occur in approximately
1:2000 elective intubations,
1:300 obstetric rapid sequence intubations
and
1:50–100 intubations in the ICU
or emergency department.
Patients do not die from lack of intubation
but from lack of ventilation and oxygenation, and all too often the anaesthetist becomes fixated on trying to intubate at the expense of resuscitating the hypoxic patient.
The Difficult Airway Society (DAS) has published guidelines on how to manage ‘the failed intubation’ scenario.
You will be expected to know
these as examiners are likely to take a very
harsh view of faltering knowledge in this crucial area.
What is a difficult intubation?
A difficult intubation is defined as one in
which an anaesthetist with at least
2 years’ training,
using a traditional laryngoscope blade,
achieves only a poor view at direct laryngoscopy (grade 3 or 4)
or requires more than three
attempts
at direct laryngoscopy or
more than 10 minutes to intubate or
additional equipment in order to secure the airway.
Difficult intubations are thought to occur in about 1 in 65 cases.
What patient factors contribute to a difficult intubation?
> Congenital, e.g. Down’s, Pierre Robin, Treacher Collins and Marfan’s syndromes
> Anatomical, e.g. morbid obesity, pregnancy, large breasts, thick, short and immobile necks,
protruding teeth,
beards and
receding jaws
> Disease, e.g. acromegaly, scleroderma, rheumatoid arthritis, airway malignancy and cervical spine fractures
> Acquired, e.g. swelling, infection, trauma and scars
How can you predict if a patient is
likely to be difficult to intubate?
Unfortunately, there is no single test
that can predict all difficult intubations
and despite pre-operative airway evaluation,
20% of all difficult intubations are not predicted.
An anaesthetic airway assessment
should encompass the following:
Review the medical records
and previous anaesthetic charts:
> Cormack and Lehane grade:
establish previous grade of intubation
(grade 3 or 4 is considered difficult)
and any airway complications.
History:
> Presenting pathology:
e.g. airway malignancies are likely to be
associated with a difficult airway.
> Medical diseases:
e.g. rheumatoid arthritis can affect the
temporomandibular joints, neck and arytenoids.
> Surgery to the neck and airway:
this can distort airway anatomy.
> Radiotherapy to the head and neck: this can distort airway anatomy and cause tissues surrounding the airway to become rigid, making head extension, jaw thrust and direct laryngoscopy very difficult.
> Anaesthesia: ask the patient whether they had any problems, such as
dental damage during previous anaesthetics.
Difficult airway on exam
Examination:
> General:
• BMI
• Beard (often covers a small, receding chin)
• Large breasts
(makes inserting the laryngoscope difficult; consider
using a short-handle laryngoscope)
> Head and neck:
- Scars
- Swellings (e.g. goitre)
- Burns or radiotherapy
- Range of neck movement
> Inter-incisor gap:
• Normal should be 5 cm or three-finger breaths
(using patient’s own fingers).
> Mallampati score:
• Performed with patient sitting up,
head in neutral position,
mouth wide open and
tongue protruding with no phonation.
• Classes I–III were first described by Mallampati in 1983 and class IV
was later added by Samsoon and Young in 1987.
There is now also a
class 0,
applicable when you can visualise the epiglottis!
> Teeth: Protruding teeth make direct laryngoscopy difficult while the edentulous patient makes face mask ventilation difficult.
> Tongue:
Large tongues,
as seen in patients with Down’s syndrome,
make inserting the laryngoscope difficult
and can obscure the view.
> Jaw slide:
• This gives an indication of the degree of mandibular subluxation that
can occur during maximal forward protrusion of the mandible.
• It is classified as
A – lower incisors lie beyond the upper incisors,
B – lower incisors meet upper incisors and
C – lower incisors remain behind upper incisors.
> Thyromental distance:
This represents the gap available
to displace the
tongue and should be ≥6.5 cm.
Radiological investigations:
Other invx
Radiological investigations:
> CT or MRI of upper airway and neck
> X-ray of mandible and cervical spine
Radiological features that may aid prediction of a difficult intubation include:
> Reduced distance between the occiput
and spine of C1
> Reduced distance between spine of C1 and C2
> Ratio of mandibular length to
posterior mandibular depth >3.6.
Other investigations:
> Flexible nasal endoscopy:
Typically performed by ENT surgeons.
Good views of the base of the tongue
and vocal cords are obtained.
> Flow–volume loops: Can help to differentiate between intrinsic and
extrinsic causes of stridor.
What is the Wilson risk
sum score?
This is a scoring system designed to predict a difficult intubation. It
comprises five risk factors each scoring between 0 and 2 points with a
maximum total of 10 points:
A score of more than 2 predicts approximately 75% of difficult intubations.
Weight
Head and neck
movement
Jaw movement
Receding mandible
Protruding teeth
What are the management options of a failed intubation?
In any failed intubation scenario,
there are four questions that must be
addressed in order to determine the
safest management option for the patient:
1
> Can the patient be ventilated?
• If the patient can be ventilated,
this allows time for help to be
summoned and intubating aids to be brought.
2
• If the patient cannot be ventilated,
the ‘can’t intubate, can’t ventilate’
algorithm from the DAS should be followed
> Is this an RSI or non-RSI technique?
• Time constraints and the risk of aspiration may complicate a failed RSI intubation.
3
> Is surgery elective or emergency?
• If surgery is elective and no immediate assistance is at hand and no advanced airway equipment set up, then the patient should be woken up and alternative options including awake fibre-optic intubation,
regional anaesthetic techniques or local anaesthetic techniques should be considered. Alternatively, surgery should be postponed.
• If immediate surgery is essential because without it the patient would incur serious morbidity or even death, provided the patient can be adequately ventilated, the safest option of maintaining the patient’s airway (e.g. LMA ProSeal™) needs to be decided.
• Remember that the examiners are asking for what you would do in this situation.
Do not jump the gun and offer them a technique with
which you are unfamiliar; tell them which technique would be safest in your hands.
4 > Is the patient pregnant? • The mother’s survival is paramount. • Two situations in which surgery may be required despite failure of intubation are maternal cardiac arrest (CPR is not effective without delivery of the baby) and imminent risk of life to the mother if surgery does not proceed (e.g. massive peri-partum haemorrhage).
Post-operatively:
Post-operatively:
> The patient should be reviewed.
> The exact nature of the difficult airway must be clearly documented in the anaesthetic notes with particular mention of ease of bag valve mask
ventilation.
> The patient must be informed of this and encouraged to alert all future anaesthetists.
> A ‘difficult airway alert’ form should be completed and given to the patient and a copy sent to the GP (the DAS website has a letter template).
DAS has published guidelines on the management of various ‘failed intubation’ scenarios. You must be well versed with these algorithms, as any evidence of
faltering knowledge is likely to lead to a failure. These guidelines are reproduced with the permission of DAS at the end of this question.
Do you know of any national
audits relating to the difficult
airway?
The fourth National Audit Project (NAP 4),
conducted by the Royal College
of Anaesthetists and DAS,
was published in 2011 and
is the world’s largest
prospective audit that looked
into the incidence of major airway complications
within the UK
(death, brain damage, surgical or needle cricothyroidotomy and
unanticipated ICU admissions related to an airway complication)
Data were
collected for 1 year between 2008 and 2009. There were two phases to the audit:
> Snapshot phase:
Performed over a 2-week period,
data on the total numbers and
types of anaesthetically related
airway interventions were collected.
These data were then extrapolated to
give the number of airway
interventions that were performed
within the UK per annum.
> Data collection phase: Performed over a 1-year period, the total number of major airway complications was collected, enabling the incidence of these complications to be calculated (data collected also for ICU and emergency departments).
Major findings of NAP4:
> 2.9 million general anaesthetics were performed in UK NHS hospitals over
the 1-year period.
The airway management for these cases were as follows:
- 56% had a supraglottic airway device (e.g. LMA)
- 38% had a tracheal tube
- 5% were managed with a face mask
> Poor airway assessment (either incomplete or with omissions) along with a failure to alter the management plan in response to the findings of these assessments contributed to poor airway outcomes.
> Poor airway planning strategies
contributed to poor airway outcomes.
Anaesthetists must have a logical
sequence of plans to manage various
airway complications.
> Awake fibre-optic intubations were
not always used when indicated.
> Problems arose when difficult intubations
were managed by multiple repeat
attempts at intubation with no change of approach.
> At least one in four major airway
events reported came from ICU or the
emergency department.
> Failure to use capnography in ventilated patients was a likely contributing factor in 70% of all ICU-related airway deaths.
> Displaced tracheostomies, and to a lesser extent tracheal tubes, were a major cause of morbidity on ICU.
> Most events in the emergency department were complications of rapid sequence induction.
DAS Algorithims
DAS
