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## Complete Summary

#### GUIDELINE TITLE

Difficult Airway Society guidelines for management of the unanticipated
difficult intubation.

#### BIBLIOGRAPHIC SOURCE(S)

Henderson JJ, Popat MT, Latto IP, Pearce AC. Difficult Airway Society
guidelines for management of the unanticipated difficult intubation.
Anaesthesia 2004 Jul;59(7):675-94. \[314 references\]
[PubMed](http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=15200543)

#### GUIDELINE STATUS

This is the current release of the guideline.

### COMPLETE SUMMARY CONTENT

 SCOPE\
 METHODOLOGY - including Rating Scheme and Cost Analysis\
 RECOMMENDATIONS\
 EVIDENCE SUPPORTING THE RECOMMENDATIONS\
 BENEFITS/HARMS OF IMPLEMENTING THE GUIDELINE RECOMMENDATIONS\
 QUALIFYING STATEMENTS\
 IMPLEMENTATION OF THE GUIDELINE\
 INSTITUTE OF MEDICINE (IOM) NATIONAL HEALTHCARE QUALITY REPORT
CATEGORIES\
 IDENTIFYING INFORMATION AND AVAILABILITY\
 DISCLAIMER

### SCOPE

#### DISEASE/CONDITION(S)

Unanticipated difficult intubation

#### GUIDELINE CATEGORY

Management

#### CLINICAL SPECIALTY

Anesthesiology\
Critical Care\
Emergency Medicine\
Surgery

#### INTENDED USERS

Physicians

#### GUIDELINE OBJECTIVE(S)

To present guidelines for the management of the unanticipated difficult
intubation in an adult non-obstetric patient, to justify the choice of
techniques, and to discuss alternative management strategies

#### TARGET POPULATION

Adult non-obstetric patients undergoing intubation

Note: Paediatric and obstetric patients, and patients with upper airway
obstruction, are excluded.

#### INTERVENTIONS AND PRACTICES CONSIDERED

1.  Direct laryngoscopy

2.  Tracheal intubation

3.  Fibreoptic tracheal intubation through intubating laryngeal mask
    airway (ILMA™) or laryngeal mask airway (LMA™) (or ProSeal LMA™)

4.  Maintenance of oxygenation and ventilation using face mask
    (postponement of surgery and awakening)

5.  Cannula or surgical cricothyroidotomy (rescue technique)

#### MAJOR OUTCOMES CONSIDERED

Not stated

### METHODOLOGY

#### METHODS USED TO COLLECT/SELECT EVIDENCE

Hand-searches of Published Literature (Primary Sources)\
Hand-searches of Published Literature (Secondary Sources)\
Searches of Electronic Databases

#### DESCRIPTION OF METHODS USED TO COLLECT/SELECT THE EVIDENCE

The published literature on difficult and failed tracheal intubation was
reviewed with extensive Medline searches and use of personal
bibliographies. Advice was sought from members who had particular
expertise or knowledge.

#### NUMBER OF SOURCE DOCUMENTS

Not stated

#### METHODS USED TO ASSESS THE QUALITY AND STRENGTH OF THE EVIDENCE

Expert Consensus

#### RATING SCHEME FOR THE STRENGTH OF THE EVIDENCE

Not applicable

#### METHODS USED TO ANALYZE THE EVIDENCE

Review

#### DESCRIPTION OF THE METHODS USED TO ANALYZE THE EVIDENCE

Not stated

#### METHODS USED TO FORMULATE THE RECOMMENDATIONS

Expert Consensus

#### DESCRIPTION OF METHODS USED TO FORMULATE THE RECOMMENDATIONS

A prototype flow-chart was presented at the Difficult Airway Society
(DAS) Annual Scientific Meeting in November 2000. There was debate and
criticism, and constructive suggestions were received at the meeting and
subsequently by electronic mail. The Disease Airway Society executive
committee examined the flow-charts in detail at several meetings.
Development was based on evidence, experience, and consensus. Revised
flow-charts were presented at the Disease Airway Society Annual
Scientific Meetings in November 2001 and 2002. There was overwhelming
support for the concept and content of the flow-charts.

#### RATING SCHEME FOR THE STRENGTH OF THE RECOMMENDATIONS

Not applicable

#### COST ANALYSIS

A formal cost analysis was not performed and published cost analyses
were not reviewed.

#### METHOD OF GUIDELINE VALIDATION

Internal Peer Review

#### DESCRIPTION OF METHOD OF GUIDELINE VALIDATION

A late version of the paper was sent for comments to 27 Difficult Airway
Society (DAS) members who had been particularly involved in the
guidelines discussions. Their comments were considered during
preparation of the final version.

### RECOMMENDATIONS

#### MAJOR RECOMMENDATIONS

**Overview**

The essence of the Difficult Airway Society (DAS) guidelines for
management of unanticipated difficult tracheal intubation is a series of
flow-charts. They should be used in conjunction with the original
guideline document.

The DAS flow-charts are based on a series of plans. The philosophy of
having a series of plans is well established in airway management, as no
single technique is always effective. Effective airway management
requires careful planning so that back up plans (plan B, C, D) can be
executed when the primary technique (plan A) fails. This philosophy
forms the basis of the DAS guidelines. It is hoped that anaesthetists
will always make back-up plans *before* performing primary techniques so
that adequate expertise, equipment, and assistance are available.

Two other principles are particularly important. Maintenance of
oxygenation takes priority over everything else during the execution of
each plan. Anaesthetists should seek the best assistance available as
soon as difficulty with laryngoscopy is experienced.

The basic structure of the DAS flow-charts is shown in figure 1 of the
original guideline document. This contains the plans and core
techniques, and shows the possible outcomes. The plans are labelled A-D:

**Plan A**: Initial tracheal intubation plan

**Plan B**: Secondary tracheal intubation plan, when Plan A has failed

**Plan C**: Maintenance of oxygenation and ventilation, postponement of
surgery, and awakening the patient, when earlier plans fail

**Plan D**: Rescue techniques for \"can\'t intubate, can\'t ventilate\"
(CICV) situation

Not all these plans are appropriate to every possible scenario (vide
infra). The outcome of each plan determines progress to subsequent
plans. In some situations, progress depends upon clinical factors, such
as the best view of the larynx. Subdivision of the Cormack & Lehane
grade 3 into 3a (epiglottis can be lifted) and 3b (epiglottis cannot be
lifted from the posterior pharyngeal wall) has a significant effect on
the success of the introducer (bougie) and fibreoptic techniques.

It was not possible to develop a single detailed flow-chart to cover all
clinical scenarios. Detailed flow-charts have therefore been developed
for each of the following:

1.  Unanticipated difficult tracheal intubation-during routine induction
    of anaesthesia in an adult patient

2.  Unanticipated difficult tracheal intubation-during rapid sequence
    induction of anaesthesia (with succinylcholine) in a non-obstetric
    patient

3.  Failed intubation, increasing hypoxaemia, and difficult ventilation
    in the paralysed, anaesthetised patient, the \"can\'t intubate,
    can\'t ventilate\" situation

The principal points of these plans are discussed in more detail.
Practical details of some techniques are outlined, but full descriptions
should be sought in the references and textbooks. The techniques should
be practised under supervision in elective situations, where
appropriate, and in manikins.

**Scenario 1: Unanticipated difficult tracheal intubation - during
routine induction of anesthesia in an adult patient** (Refer to figure 2
of the original guideline document for a flow chart depicting this
scenario.)

This is the clinical scenario of difficult intubation in an adult
patient after induction of general anaesthesia and muscle paralysis,
usually with a non-depolarising neuromuscular blocking drug.

*Plan A: Initial tracheal intubation plan*

The first attempt at direct laryngoscopy should always be performed in
optimal conditions after ensuring adequate muscle relaxation and
appropriate position of the head and neck (normally the \"sniffing\"
position of head extension and neck flexion). Use of optimum external
laryngeal manipulation (OELM) or backward, upward, and rightward
pressure (BURP) on the thyroid cartilage, if required, applied with the
anaesthetist\'s right hand, should be an integral part of this first
attempt. If, despite these measures, there is still a grade 3 or 4 view,
then alternative techniques will be needed. These techniques include use
of an introducer (\"gum elastic bougie\") and/or a different
laryngoscope. Alternative direct laryngoscopes of proven value include
the McCoy and straight laryngoscopes. The choice of technique depends
upon the experience of the anaesthetist with a particular technique.
Oxygenation is maintained with mask ventilation between intubation
attempts.

The Eschmann tracheal tube introducer (\"gum elastic bougie\") was
designed for multiple use and was marketed in the United Kingdom (UK) in
the early 1970s. It differs from previous introducers in its greater
length (60 cm), angled tip, and the combination of flexibility and
malleability. It is inexpensive and readily available, and the technique
combined simplicity of operation with a high success rate. It is passed
blindly into the trachea when the laryngeal inlet is not visible. The
most widely used technique in the UK is the combination of the
multiple-use bougie (introducer) with the Macintosh laryngoscope. There
is evidence that the bougie is more effective than the stylet when the
best view of the larynx is grade 3.

The bougie technique should be used in an optimal way. The Macintosh
laryngoscope is left in the mouth and attempts are made to insert the
bougie blindly into the trachea. It is important to maximise the chance
of the bougie entering the trachea. The anaesthetist will not see the
bougie entering the larynx when the laryngoscopy view is grade 3 or 4.
Therefore it is important to be able to recognise whether the bougie is
in the trachea or the oesophagus. Clicks can often be felt by the
anaesthetist when the bougie is passed into the trachea. These are
caused by the tip of the bougie hitting the tracheal cartilages. Clicks
are more likely to be elicited if the distal end of the bougie is bent
into a curve of about 60 degrees. If clicks are present, proceed with
intubation by passing (\"railroading\") the tube over the bougie (vide
infra). Clicks will not be present if the bougie goes down the center of
the tracheal lumen or is in the oesophagus. If clicks are not elicited,
the bougie should be advanced gently to a maximum distance of 45 cm. If
distal hold-up is sensed as slight resistance to further advancement,
indicating that the bougie is held up in the bronchial tree, proceed
with intubation. If the patient is not fully paralysed, coughing may
indicate the presence of the bougie in the trachea. If neither clicks,
hold-up, nor coughing are elicited, the bougie is probably in the
oesophagus. Remove the bougie and consider another attempt at passing
the bougie blindly into the trachea-if the laryngeal view is 3a.

Once the bougie is in the trachea, the tracheal tube is railroaded over
the bougie. Railroading is facilitated if the laryngoscope is kept in
the mouth and the tube is rotated 90 degrees anticlockwise. Use of a
small tube, reinforced tube, the tube (Euromedical ILM) supplied with
the Intubating Laryngeal Mask, and the Parker tube have all facilitated
railroading in flexible fibreoptic intubation. By analogy, it is
probably that these tube factors will facilitate railroading with the
Eschmann introducer.

Success rates with the original reusable Eschmann introducer in
prospective studies have varied between 94.3%, 99.5%, and 100%. Optimum
results depend on regular use and experience. However, the technique is
of limited value when it is not possible to elevate (grade 3b) or
visualise (grade 4) the epiglottis. There are concerns that some
recently introduced single-use disposable introducers are not as
effective as and may cause more trauma than the original multiple-use
bougie.

Alternative techniques of laryngoscopy, of proven value, may be used by
those experienced in these techniques. In particular there is
considerable evidence of the value of the following techniques in
experienced hands:

-   Direct use of the flexible fibreoptic laryngoscope

-   Bullard-type laryngoscope

There are situations in which these techniques can offer unique
advantages. The lighted stylet is not a visual technique, but may be
successful in experienced hands.

Multiple and prolonged attempts at laryngoscopy and tracheal intubation
are associated with morbidity and mortality. The extent of laryngeal
oedema may not become apparent until fibreoptic examination or
extubation. An essential component of Plan A is therefore to limit the
number and duration of attempts at laryngoscopy in order to prevent
trauma and development of a \"can\'t ventilate\" situation. It is
difficult to justify use of the same direct laryngoscopy more than
twice, and the maximum number of laryngoscope insertions should be
limited to four. However, tracheal intubation may be successful when it
is performed by a more experienced anaesthetist and one such additional
attempt is worthwhile.

When these attempts at tracheal intubation have been unsuccessful, Plan
B should be implemented.

*Plan B: Secondary Tracheal Intubation Plan*

A different approach is required when direct laryngoscopy has failed.
Alternative techniques can allow continuous ventilation and oxygenation
both *during* and *between* intubation attempts. This is best achieved
by using a \"dedicated airway device,\" defined as \"an upper airway
device which maintains airway patency while facilitating tracheal
intubation.\" Although the classic laryngeal mask airway (LMA™) has been
recommended as a ventilation and intubation device in patients with a
difficult airway, it was not designed as a conduit for tracheal
intubation and has clear limitations when used for this purpose (*vide
infra*). Any other supraglottic airway device could be used, but the
intubating laryngeal mask (ILMA™) was designed specifically to
facilitate tracheal intubation while maintaining ventilation. Each of
these devices has advantages and disadvantages.

*ILMA™ for secondary tracheal intubation*: Numerous reports have
confirmed the effectiveness of the ILMA™ for both ventilation and blind
intubation in patients *without* airway difficulties. The overall
intubation success rate in 1,100 patients in these studies was 95.7%.
Further studies have confirmed its value in management of patients with
*known* or *anticipated* difficult tracheal intubation. The ILMA™ has
also proved to be a useful device in the management of *unanticipated*
difficult intubation. In one study, blind intubation was performed in 20
out of 23 patients with a 75% success rate at the first attempt (10%
required two or three attempts and 5% required four attempts) and 100%
overall success rate. Fibreoptic guided intubation was successful at the
first attempt in the remaining three patients.

Although high success rates can be achieved with a blind technique,
several attempts may be required and the incidence of oesophageal
intubation can be up to 5%. Transillumination techniques may improve
first-attempt success rates and certainly reduce the number of
manoeuvres required, the incidence of oesophageal intubation, and the
time required to achieve intubation. However, intubation under vision
through the ILMA™ using a flexible fibreoptic laryngoscope has real
advantages. The first-attempt and overall success rates are higher than
blind techniques, and it nearly always succeeds when blind intubation
fails.

The techniques of insertion and intubation through the ILMA™ differ in
many respects from the classic LMA™, and training and practice are
essential if it is to be used to achieve a high success rate and
minimise trauma in the unanticipated difficult tracheal intubation. A
learning curve of about 20 insertions has been described. The
manufacturer\'s instruction manual describes the insertion and
intubation techniques, the adjustments necessary for ideal positioning
of the device, and an approach to problem-solving. The \"Chandy
manoeuvre\" (alignment of the internal aperture of ILMA™ and the glottic
opening by finding the degree of sagittal rotation which produces
optimal ventilation, and then applying a slight anterior lift with the
ILMA™ handle) facilitates correct positioning and blind intubation
through the ILMA™ and has been shown to reduce the number of intubation
attempts. Use of the dedicated silicone tracheal tube is strongly
recommended. The fibrescope can be used to visualise the \"Epiglottic
Elevator Bar\" lifting the epiglottis and observe passage of the
tracheal tube through the glottis or it can be passed into the trachea
after glottic visualisation and then used to railroad the tube. The DAS
prefers the latter technique. The lubricated silicone tracheal tube is
first inserted into the shaft of the ILMA™ until its tip reaches the
mask aperture (indicated by the transverse line on the tube). The
fibrescope is then inserted through the tracheal tube so that its tip is
just within the tip of the tube. The tube and fibrescope are then
advanced together for about 1.5 cm so that the \"Epiglottic Elevator
Bar\" is seen to elevate the epiglottis. Once the tip of the tube is in
the larynx, the fibrescope is advanced into the trachea and the tube is
then railroaded over it. Finally, the position of the tube is checked
with the fibrescope during withdrawal. Oxygen and anaesthetic gases can
be delivered continuously if a self-sealing bronchoscope connector is
attached between the 15-mm tracheal tube connector and the anaesthetic
breathing system. Ventilation is maximised by using a wide tracheal tube
with a narrow fibrescope. The ILMA™ should be removed when tracheal
intubation has been verified and the tracheal tube secured.

*Classic LMA™ for secondary tracheal intubation*: Fibreoptic tracheal
intubation through the classic LMA™ (the role of the single-use LMA™ in
management of the difficult airway patient has not been established)
should be considered when ILMA™ is not available. Although Heath
reported a 93% success rate for blind intubation through the LMA™ (in
the absence of cricoid pressure), others have achieved much lower
success rates, and blind intubation cannot be recommended. Success rates
of 90 to 100% (depending on technique, equipment, number of attempts
allowed and experience of user) can be achieved with fibreoptic
intubation through the classic LMA™. The limitations of the classic LMA™
as a conduit for intubation are well known and include the following:

-   The LMA™ tube connector is narrow and will allow for a 6-mm
    (internal diameter \[ID\]) tracheal tube through a size 3 or 4 LMA™
    and 7 mm (ID) through a size 5 LMA™

-   The LMA™ tube is so long that the cuff of an uncut normal tracheal
    tube (26 to 27 cm) may lie between the vocal cords so that it is
    ineffective and potentially traumatic. A long flexometallic tube,
    nasal RAE or a microlaryngeal tube is recommended.

-   The mask aperture bars may obstruct the passage of the tracheal tube

-   Manipulation requires head and neck movement and/or finger
    insertion, both of which may worsen difficulties.

Difficulties may be encountered during subsequent removal of the LMA™.
The LMA™ may be left in situ if its presence does not interfere with
surgical access. Techniques of LMA™ removal without dislodging the
tracheal tube have been described, but they may fail and expose the
patient to avoidable danger.

The problems mentioned above can be avoided by using a two-stage
technique with a flexible fibreoptic laryngoscope and an Aintree
Intubation Catheter.

Whatever technique of tracheal intubation through a \"dedicated airway\"
is used, the vocal cords should be open and non-reactive before
attempting to advance the fibrescope or tracheal tube into the trachea.
If two attempts at the secondary tracheal intubation technique fail,
surgery should be postponed, and the patient awakened (i.e., Plan C
should be implemented).

*Plan C: Maintenance of Oxygenation and Ventilation, Postponement of
Surgery, and Awakening the Patient-If Plans A and B Have Failed*

If Plan B (secondary tracheal intubation technique) fails, it remains
important to avoid trauma to the airway and to maintain ventilation and
oxygenation with the dedicated airway device. Elective surgery should be
cancelled and the airway device should be removed only after muscle
relaxation has been reversed, spontaneous ventilation is adequate, and
the patient is awake. An alternative plan for anaesthesia can then be
made. Although it may be possible to perform surgery under regional
anaesthesia, the safest plan is to secure the airway with the patient
awake. If adequate ventilation and oxygenation cannot be achieved with
the dedicated airway device, ventilation should be performed using a
face mask with or without an oral or nasal airway.

If ventilation is impossible and serious hypoxaemia is developing, then
Plan D (Rescue techniques for CICV situation) should be implemented
without delay (*vide infra*).

**Scenario 2: Unanticipated Difficult Tracheal Intubation-During Rapid
Sequence Induction of Anaesthesia (with Succinylcholine) in a
Non-Obstetric Patient** (Refer to figure 3 of the original guideline
document for a flow-chart depicting this scenario.)

*Plan A: Initial Tracheal Intubation Plan*

In scenario 2, in contrast to scenario 1, there is an increased
likelihood of regurgitation or vomiting, with a consequent risk of
pulmonary aspiration. The change in management involves the use of
pre-oxygenation and the application of cricoid pressure. It is
particularly important to use a pre-oxygenation technique which
maximises oxygen stores.

Cricoid pressure has played an important role in the prevention of
pulmonary aspiration since its introduction by Sellick. It is an
integral part of the flow-chart for the patient having rapid sequence
induction. However, it can impair insertion of the laryngoscope, passage
of an introducer and can cause airway obstruction. A force of 30 Newtons
(N) provides good airway protection while minimising the risk of airway
obstruction, but it is not well tolerated by the conscious patient.
Cricoid pressure should be applied with an initial force of 10 N when
the patient is awake, increasing to 30 N as consciousness is lost. The
force should be reduced, with suction at hand, if it impedes
laryngoscopy or causes airway obstruction.

The principles of optimising the initial tracheal intubation technique,
and use of the Eschmann introducer and alternative direct laryngoscopes,
are the same as in Plan A in the elective patient. If intubation fails
despite a maximum of three attempts, a failed intubation plan with the
aim of maintaining oxygenation and awakening the patient (Plan C) is
initiated immediately. Further doses of succinylcholine should not be
given.

*Plan C: Maintenance of Oxygenation and Ventilation and Postponement of
Surgery, If Possible*

Plan B is omitted from airway management of the patient having rapid
sequence induction for two reasons. The risk of regurgitation or
vomiting is greater than in the elective patient, so that the risk of
aspiration during further attempts at tracheal intubation is higher. The
short duration of succinylcholine increases the risk of laryngospasm and
difficulty with laryngoscopy during recovery of neuromuscular function,
so that further tracheal intubation attempts increase the risk to the
patient. When initial attempts at tracheal intubation in this scenario
fail, the safest plan in most patients is to postpone surgery and awaken
the patient.

Plan C of this scenario contains two subsidiary scenarios, in which the
urgency of proceeding with surgery differs. A risk-benefit assessment
balances the risks of delaying the surgery against the risk of
proceeding with a suboptimal airway. If it is essential to proceed with
the surgery, the traditional technique has been to continue with a face
mask and oral airway, maintaining cricoid pressure. Continuation of
anaesthesia with a classic LMA™ is now an established technique,
although not always effective or accepted (effect of cricoid pressure on
LMA™ insertion - *vide infra*). If it proves difficult to ventilate the
lungs as a consequence of gas leakage past the cuff of the classic LMA™,
use of the ProSeal LMA™ should be considered. The ProSeal LMA™ forms a
better seal than the classic LMA™ and provides improved protection
against aspiration. The potential advantages of the ProSeal LMA™ have to
be offset against increased complexity of insertion (not a problem when
a precise technique and the insertion tool are used). The risk (about
5%) of airway obstruction may be lower than that with the classic LMA™.
Airway obstruction may be overcome by reinsertion, use of a smaller
size, withdrawal of air from the cuff and/or moving the head and neck
into the sniffing position. However, poor seal and airway obstruction
may be significant problems in some obese patients.

Wherever possible the aim should be to postpone surgery and awaken the
patient. Maintenance of ventilation and oxygenation with a face mask is
a conventional technique. This may include the one- or two-person
technique and the use of an oral or nasal airway. A narrow, soft,
lubricated nasopharyngeal airway may be inserted gently if this can be
done without trauma. It may be necessary to reduce cricoid force in
order to achieve satisfactory ventilation. If satisfactory oxygenation
(e.g. oxygen saturation \[S~p~o~2~\] \>90% with a fraction of inspired
oxygen \[F~i~o~2~\] of 1.0) cannot be achieved with a face mask, the
LMA™ should be used. Cricoid force impedes positioning of and
ventilation through the LMA™. It may be necessary to reduce cricoid
force during LMA™ insertion when it is used in an emergency.

If ventilation is impossible and serious hypoxaemia is developing, then
Plan D (Rescue techniques for CICV situation) should be implemented
without delay.

**Scenario 3: Failed Intubation, Increasing Hypoxaemia, and Difficult
Ventilation in the Paralysed Anaesthetised Patient**

*Plan D: Rescue Techniques for CICV Situation* (Refer to figure 4 of the
original guideline document for a flow chart depicting this scenario.)

This scenario may develop rapidly, but often occurs after repeated
unsuccessful attempts at intubation in scenarios 1 and 2, where a \"can
ventilate\" situation develops into a CICV situation. It is probable
that most patients who suffer hypoxic damage pass through a CICV stage.
In situations where mask ventilation fails to oxygenate the patient, the
upper airway is normally sufficiently patent to allow gas to escape
upwards. This has an important bearing on the efficacy of different
airway rescue techniques (*vide infra*).

Before resorting to invasive rescue techniques, it is essential that a
maximum effort has been made to achieve ventilation and oxygenation with
non-invasive techniques, such as optimum mask ventilation and the LMA™.

Other supraglottic airway devices, particularly the Combitube™, have
been used in the CICV situation. Satisfactory placement of the Combitube
is not always possible, even when inserted with a laryngoscope. When
properly positioned, it allows ventilation with a higher seal pressure
than the classic LMA™, protects against regurgitation, and allows
subsequent attempts at intubation while the inflated oesophageal cuff
maintains airway protection. Although there have been failures, the
Combitube has been used successfully in the difficult intubation and the
CICV situation, including failure with the LMA™. Adjustment of cuff
pressure may be necessary. The Combitube is a large and bulky device,
and there have been some reports of oesophageal damage with the original
product, but the risk should be lower with the SA (Small Adult) size.
The decision to use the Combitube will depend on availability,
experience, and clinical situation.

The risks of an invasive rescue technique must be constantly weighed
against the risks of hypoxic brain damage or death. Rapid development of
severe hypoxaemia, particularly associated with bradycardia, is an
indication for imminent intervention with an invasive technique. Once
the decision to perform an invasive technique is made, it is essential
to use an effective technique. Rapid reoxygenation is now necessary, and
this is best achieved with a combination of an invasive airway device
and a ventilation technique which is capable of reliably delivering a
large minute volume with an F~i~o~2~ of 1.0. Many cricothyroidotomy
techniques have been criticised because they are not capable of
providing effective ventilation.

Classical emergency surgical tracheostomy involves incision through skin
and platysma, division of the isthmus of the thyroid gland, haemostasis,
incision of the tracheal cartilage, and insertion of a cuffed
tracheostomy tube. Emergency tracheostomy can be very difficult and have
serious complications. A few surgeons may succeed in 3 minutes, but most
will take longer. Delay in completion of tracheostomy in this situation
results in death of the patient.

There are a few case reports of successful use of percutaneous
tracheostomy techniques in the failed intubation and CICV situation.
However, percutaneous tracheostomy techniques include a number of steps
and can take time.

The anaesthetist must be prepared to use invasive techniques to secure
the airway via the cricothyroid membrane. Success depends on
understanding the anatomy of the cricothyroid membrane and of the
factors which determine the efficacy of ventilation with different
airway devices.

Invasive airway devices which are frequently recommended include:

-   Cuffed tracheal or tracheostomy tubes

-   Narrow (4 to 6 mm ID) uncuffed tubes

-   Cannulae

These must be matched to the ventilation technique in order to provide a
system which can deliver a large minute volume. When a cuffed tube is
used, a low-pressure ventilation system is satisfactory. When a 4-mm
(ID) uncuffed tube is used, successful ventilation is less certain. The
\"inflated\" gas may enter the lungs or flow out through the upper
airway. Factors which promote entry of gas into the lungs include high
resistance in the upper airway, high lung compliance, high flow rate,
and long inflation time. The limitations of the uncuffed tubes in the
CICV situation are well summarised by Walls. When a cannula is used, a
high-pressure ventilation source is necessary. This system is discussed
clearly by Dworkin.

All current airway guidelines recommend management of the CICV situation
using:

-   Cannula cricothyroidotomy with percutaneous transtracheal jet
    ventilation (TTJV) or;

-   Surgical cricothyroidotomy

They remain the standard techniques.

*Cannula cricothyroidotomy*: Cannula cricothyroidotomy involves the
combination of insertion of a cannula through the cricothyroid membrane
with high-pressure ventilation. It can provide effective ventilation,
although low success rates have been reported. The DAS recommends use of
kink-resistant cannulae because standard intravenous cannulae are easily
kinked. The technique is summarised in the flow-chart and is described
in detail by Benumof and Stewart. Verification of correct cannula
placement by aspiration of air into a large syringe, before the use of
high-pressure ventilation, is essential. Subsequent dislodgement of the
cannula must be prevented.

A high-pressure source is needed to achieve effective ventilation
through a cannula. The oxygen flush systems of most modern anaesthesia
machines do not provide sufficient pressure and an adjustable
high-pressure device (driven by gas pipeline pressure) with a Luer Lock
connection is recommended. Barotrauma is less likely if an initial
inflation pressure of less than 4 kilopascals (kPa) (55 pounds per
square inch \[psi\]) is used. Some have recommended insertion of a
second cannula to facilitate exhalation. However, the driving pressure
for exhalation is relatively low and use of a second cannula is not a
reliable means of relieving high airway pressure. Initial high-pressure
ventilation should be performed particularly cautiously. It is important
to keep the upper airway as open as possible and to verify deflation of
the lungs and exhalation through the upper airway. If an LMA has been
used, it should be kept in place to facilitate exhalation.

*Surgical cricothyroidotomy*: Surgical (\"stab\") cricothyroidotomy can
allow rapid restoration of ventilation and oxygenation in the CICV
situation and is included in advanced trauma life support (ATLS) and
military training. Anaesthetic deaths could be prevented by appropriate
use of surgical cricothyroidotomy. Emergency cricothyroidotomy can
result in serious complications, although these are infrequent when
staff are well trained. The technique uses low-pressure ventilation
through a cuffed tube in the trachea.

A simplified cricothyroidotomy technique can be performed in 30 seconds.
This 4-step technique consists of:

**Step 1:** Identification of the cricothyroid membrane

**Step 2:** Horizontal stab incision (No. 20 scalpel) through skin and
membrane

**Step 3:** Caudal traction on the cricoid membrane with a tracheal hook

**Step 4:** Intubation of the trachea

The advanced trauma life support (ATLS) cricothyroidotomy technique
includes blunt dilation of the incision made in step 2. It is important
to avoid endobronchial intubation when a tracheal tube is used.

Cricothyroidotomy is sometimes particularly difficult in the obese
patient. Insertion of the tube can be facilitated by passage of an
introducer (bougie) through the incision or use of a tracheal retractor.

Guidewire techniques of cricothyroidotomy have been developed. Some
claim that these can restore the airway as quickly as the standard
surgical technique, while others have found the guidewire technique to
take longer, and to be less satisfactory, as a consequence of kinking of
the wires. It has recently been shown that the technique can be
performed in 40 seconds after practice in a manikin. The Melker™
guidewire intubation set is now available with a cuffed tube. This
technique seems promising but further reports are needed before it can
be considered a core rescue technique.

Cannula and surgical cricothyroidotomy each have advantages and
disadvantages. Cannula cricothyroidotomy involves a smaller incision
with less risk of bleeding. It may be the technique of choice when
dedicated equipment is immediately available and staff are trained in
its use. If it cannot be performed rapidly, is ineffective, or causes
complications, surgical cricothyroidotomy should be performed
immediately. Surgical cricothyroidotomy is more invasive. It can be
performed very rapidly and will allow effective ventilation with
low-pressure sources.

Invasive airway access is a temporary measure to restore oxygenation.
Definitive airway management will follow. This may be a formal
tracheostomy, but tracheal intubation will be possible in some patients.

#### CLINICAL ALGORITHM(S)

Clinical algorithms are provided in the original guideline document for:

-   The basic structure of the Difficult Airway Society (DAS) guideline
    flow-chart

-   The management of unanticipated difficult tracheal intubation during
    routine induction of anaesthesia in an adult patient

-   The management of unanticipated difficult tracheal intubation during
    rapid sequence induction of anaesthesia (with succinylcholine) in a
    non-obstetric patient

-   The management of failed intubation, increasing hypoxaemia and
    difficult ventilation in the paralysed anaesthetised patient

### EVIDENCE SUPPORTING THE RECOMMENDATIONS

#### TYPE OF EVIDENCE SUPPORTING THE RECOMMENDATIONS

Controlled studies cannot be performed in unanticipated difficult
intubation. The evidence basis of these guidelines best fits the
description of expert committee reports, opinions, and experience. All
Difficult Airway Society recommendations are supported by at least two
case reports or series, the strongest evidence available for infrequent
emergency situations.

### BENEFITS/HARMS OF IMPLEMENTING THE GUIDELINE RECOMMENDATIONS

#### POTENTIAL BENEFITS

Reduce the incidence of airway trauma and hypoxaemic damage associated
with unanticipated difficult intubation and result in better outcomes
for patients

#### POTENTIAL HARMS

-   The Combitube is a large and bulky device, and there have been some
    reports of oesophageal damage with the original product, but the
    risk should be lower with the SA (Small Adult) size.

-   Emergency tracheostomy can be very difficult and have serious
    complications. A few surgeons may succeed in 3 minutes, but most
    will take longer. Delay in completion of tracheostomy in this
    situation results in death of the patient.

### QUALIFYING STATEMENTS

#### QUALIFYING STATEMENTS

It is not intended that these guidelines should constitute a minimum
standard of practice, nor are they to be regarded as a substitute for
good clinical judgment.

### IMPLEMENTATION OF THE GUIDELINE

#### DESCRIPTION OF IMPLEMENTATION STRATEGY

The techniques which have been recommended in these plans should be an
integral part of initial and continuing airway training. This can be
achieved by acquisition of knowledge in classroom teaching, learning
practical skills using manikins in workshops, and use in clinical
practice, when appropriate.

There are equipment implications in these guidelines. All the equipment
described should be available for regular practice. A cart containing
the equipment should be located no more than a couple of minutes from
every location where anaesthesia is administered. Recommended equipment
lists will be published on the Difficult Airway Society (DAS) Web Site
([http://www.das.uk.com](http://www.das.uk.com/)).

#### IMPLEMENTATION TOOLS

Clinical Algorithm

For information about
[availability](#identifying-information-and-availability), see the
\"Availability of Companion Documents\" and \"Patient Resources\" fields
below.

### INSTITUTE OF MEDICINE (IOM) NATIONAL HEALTHCARE QUALITY REPORT CATEGORIES

#### IOM CARE NEED

Staying Healthy

#### IOM DOMAIN

Effectiveness\
Safety\
Timeliness

### IDENTIFYING INFORMATION AND AVAILABILITY

#### BIBLIOGRAPHIC SOURCE(S)

Henderson JJ, Popat MT, Latto IP, Pearce AC. Difficult Airway Society
guidelines for management of the unanticipated difficult intubation.
Anaesthesia 2004 Jul;59(7):675-94. \[314 references\]
[PubMed](http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=15200543)

#### ADAPTATION

Not applicable: The guideline was not adapted from another source.

#### DATE RELEASED

2004 Jul

#### GUIDELINE DEVELOPER(S)

Difficult Airway Society - Medical Specialty Society

#### SOURCE(S) OF FUNDING

Difficult Airway Society

#### GUIDELINE COMMITTEE

Not stated

#### COMPOSITION OF GROUP THAT AUTHORED THE GUIDELINE

*Primary Authors*: J.J. Henderson, Anaesthetic Department, Gartnavel
General Hospital, Glasgow, UK; M.T. Popat, Nuffield Department of
Anaesthetics, John Radcliffe Hospital, Headington, Oxford, UK; I.P.
Latto, Anaesthetic Department, University Hospital of Wales, Heath Park,
Cardiff, UK; A.C. Pearce, Anaesthetic Department, Guy\'s Hospital,
London, UK

#### FINANCIAL DISCLOSURES/CONFLICTS OF INTEREST

*Conflict of interest*: Various companies manufacturing/distributing
equipment mentioned in the guidelines have contributed to meetings and
workshops held by the Difficult Airway Society (DAS) or by the authors.
Neither the Difficult Airway Society nor any of the authors have any
commercial links with any of these companies.

#### GUIDELINE STATUS

This is the current release of the guideline.

#### GUIDELINE AVAILABILITY

Electronic copies: None available

Print copies: Available from John Henderson, Department of Anaesthesia,
Western Infirmary, 1051 Great Western Road, Glasgow G12 0YN

#### AVAILABILITY OF COMPANION DOCUMENTS

None available

#### PATIENT RESOURCES

None available

#### NGC STATUS

This NGC summary was completed by ECRI on February 9, 2005.

#### COPYRIGHT STATEMENT

This NGC summary is based on the original guideline, which is subject to
the guideline developer\'s copyright restrictions.

### DISCLAIMER

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Date Modified: 11/3/2008