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techniques ‘should be considered’.
techniques ‘should be considered’.


[[File:CICV_Algorithm.jpg|800px|center|thumb|Figure 3: Can’t intubate can’t ventilate algorithm. Reproduced with kind permission of Association of Paediatric Anaesthetists ]]
[[File:Difficult Tracheal Intubation Algorithm.jpg|800px|center|thumb|Figure 2: Difficult tracheal intubation algorithm. Reproduced with kind permission of Association of Paediatric Anaesthetists]]




Table 1. Classification of rigid indirect laryngoscopes


Classification Description of technique Examples
‘Non-guided’ devices Provide an indirect view of larynx but require direction
of tracheal tube towards larynx.
Bullard laryngoscope
Glidescope
Storz DCI Videolaryngoscope
Storz C-MAC laryngoscope
‘Guided’ devices Provide indirect view and act as a conduit for passage
of tracheal tube.
Airtraq
Optical stylets Provide indirect view via rigid or semi-rigid stylet, with
a ‘loaded’ tracheal tube for railroading.
Bonfils and Brambrink
Shikani
Lightwand


Alternate techniques
Traditional laryngoscopes (curved, straight or McCoy levering blades)
give a direct view of the larynx. Alternate techniques use an indirect
approach with flexible or rigid equipment.
• Flexible indirect laryngoscopy, in the form of fibreoptic intubation,
is the established ‘gold standard’ for the management of the
predicted difficult airway in adults (see below).
• New rigid indirect laryngoscopes are available, including in
paediatric sizes. Rigid indirect laryngoscopy has a place in the
unexpected difficult tracheal intubation algorithm. The choice of
device depends on local availability and expertise.
If visualising the larynx is impossible, then an LMA should be inserted.
LMAs provide a clear airway in the vast majority of children. This
allows delivery of ventilation, oxygenation and anaesthetic gases with
a lower risk of gastric insufflation. The LMA may also be used as a conduit for fibreoptic intubation (FOI) where necessary, or in older
children, the specifically designed intubating LMA, may be used.
If LMA insertion fails, then oxygenation and ventilation must be
provided by mask ventilation.
3. Cannot intubate, cannot ventilate (CICV) - ‘rescue
techniques’
A simple algorithm for the management of ‘cannot intubate, cannot
ventilate’ is given in Figure 3 : Can’t intubate can’t ventilate algorithm.
http://www.apagbi.org.uk/sites/default/files/images/APA3-CICVFINAL.
pdf
Rescue techniques for the CICV situation have been extensively
researched in the adult literature, but their use in paediatric emergencies
is more anecdotal than evidence-based. The choice is between a surgical
or needle (cannula) technique for cricothyroidotomy. The technique
for cannula cricothroidotomy is shown in Figure 3, and for surgical




[[File:CICV_Algorithm.jpg|800px|center|thumb|Figure 3: Can’t intubate can’t ventilate algorithm. Reproduced with kind permission of Association of Paediatric Anaesthetists ]]
[[File:CICV_Algorithm.jpg|800px|center|thumb|Figure 3: Can’t intubate can’t ventilate algorithm. Reproduced with kind permission of Association of Paediatric Anaesthetists ]]
Table 2. Technique for surgical cricothyroidotomy
1. Position the patient so that the neck is fully extended so that the trachea and larynx are pushed forward
2. Locate the cricothyroid membrane and stabilise the trachea
3. With a scalpel blade make a stab incision through the skin and cricothyroid membrane*
4. Insert a tracheal hook or retractor at the lower edge of the incision
5. Pass an appropriately sized tracheal or tracheostomy tube
6. Ventilate patient and assess effectiveness
7. Secure the tube
Arterial forceps, the scalpel blade and tracheal dilators may be used to dilate the orifice
cricothyroidotomy, in Table 2.
Since there is no randomised controlled trial of one technique versus
another, the choice should be determined by local experience and
availability of equipment. This includes utilising the surgeon who may
be more experienced than the anaesthetist. Adult evidence suggests
surgical cricothyroidotomy is preferable, so this is recommended in
older children.
The important factor is that at least one technique is actually attempted
by someone in the CICV situation when the oxygen saturations are
less than 80% and falling and/or the heart rate is decreasing.
The CICV situation is a particular challenge in infants and small
children, due to important anatomical differences:
• The trachea is small, elastic, flaccid and mobile, and so prone to
collapse during insertion of a transtracheal device.
• The cricothyroid membrane is much smaller, with an average size
of only 2.6 x 3mm, smaller than the smallest tracheal tubes.
• It is more difficult to locate the cricothyroid membrane than in
adults due to a differing orientation of the hyoid bone and the
cricoid and thyroid cartilage. This orientation also increases the
chance of laryngeal trauma during cricothyroidotomy.
• It is easier to locate the space between the tracheal rings rather
than the cricothyroid membrane.
Together these factors mean it may be more appropriate in infants
and small children to perform a surgical tracheostomy.
All ‘rescue techniques’ have significant potential for complications so
should only be performed in life threatening situations. Clearly, all the
steps for difficult facemask ventilation should be tried first. If muscle
relaxants have been used and can be reversed, wake the child up.
THE EXPECTED DIFFICULT AIRWAY
If the preoperative airway assessment alerts the anaesthetist to expected
difficulties in airway management then there are three key questions:
1. Does the anaesthetist have the necessary paediatric airway
experience?
2. Does the hospital have the necessary paediatric equipment?
3. Does the relative benefit of the planned surgery outweigh the
possible risks of anaesthesia?
If there is any doubt, full discussion should take place with the parents
(or carers), child, surgeons and anaesthetists. It may be appropriate
for the child to be referred to specialist hospital or wait for a more
experienced paediatric anaesthetist to attend.
The anaesthesia plan must be carefully considered, including what to
do if tracheal intubation is unsuccessful; will the child be woken up,
or will a tracheostomy be necessary. The anaesthesia plan should be
communicated clearly to the whole theatre team including surgeons
and nursing staff. Difficult airway equipment must be checked and
prepared.
The primary plan for management of the expected difficult paediatric
airway will likely be one of the following:
1. Laryngoscopy anticipated to be difficult but may be possible:
Attempt laryngoscopy and intubation. If fails, consider
repositioning and try alternate laryngoscopes if available, or insert
LMA and perform fibreoptic intubation (FOI) via LMA.
2. Laryngoscopy predicted to be impossible: Perform nasal FOI or
insert LMA and perform FOI via LMA.
3. Laryngoscopy and LMA insertion known to be impossible:
perform nasal FOI.
4. Laryngoscopy, LMA insertion and nasal FOI not available
or known to be impossible: perform tracheostomy either using
inhalational anaesthesia via face mask or intravenous ketamine
especially if face mask anaesthesia impossible.
Blind intubation through an LMA is NOT recommended in children
due to risk of airway trauma. Attempts at FOI should be limited to two
and if unsuccessful, consider waking child, or continue with surgical
procedure on an LMA. In situations where LMAs are unavailable,
ventilation by face mask is the alternative. If neither LMAs nor FOI
are available, the surgeon and anaesthetist need to discuss whether
the benefits of surgery outweigh the risk of attempting anaesthesia
in a child with a known difficult airway with insufficient equipment
to provide safe management. This is a very difficult decision and will
depend on the individual merits of each case.
Premedication
The use of sedative premedication in a child with a potential airway
problem is controversial. A frightened, screaming child producing
lots of secretions and in whom it is difficult to place monitoring,
intravenous cannula, and even approach to do an inhalational
induction, is also a risk.
Therefore, a small dose of sedative premedication, such as midazolam
0.3-0.5mg.kg-1 is often appropriate. Atropine is useful as an antisialogue
(30-40 micrograms.kg-1 PO or 20 micrograms.kg-1 IM). Peak effect of
atropine is 90 minutes if given PO, 25 minutes if given IM.
Anaesthetic technique
The most important principle in managing the difficult airway in
children is to maintain spontaneous ventilation until the airway is
secure.
‘Awake’ techniques require good patient co-operation, which is rarely
possible in children. Therefore, the child must be anaesthetised so the
choice is between an inhalational or intravenous technique. The variety
of airway problems encountered in children means the anaesthetic
must be tailored to the individual situation:
• Large extraoral tumours may mean a face mask will not fit
the child’s face, so an inhalational induction is impossible and IV
induction/sedation must be used instead.
• Large intraoral tumours prevent laryngoscopy and the use of an
LMA - nasal fibreoptic intubation (FOI) should be used.
• Conditions such a noma (cancrum oris) often cause severe
limitation of mouth opening - nasal FOI is likely to be required.
• Other problems such as partial mouth opening, severe retrongathia
or bony abnormalities (ameloblastoma) often make laryngoscopy
difficult but do permit the insertion of an LMA if laryngoscopy
proves impossible.
• Burns contractures causing fixed flexion of the neck may be
released prior to intubation using ketamine anaesthesia and with
local infiltration.
The variety of clinical conditions mean a one-size-fits all approach is
impossible. The best technique will depend on the equipment and
expertise available, as well as the nature of the difficult airway.
Inhalational induction, using halothane or sevoflurane in 100%
oxygen, is generally recommended Intravenous access may be
established either before or after induction but must occur before
airway instrumentation. The general technique is to deepen anaesthesia
until laryngoscopy is tolerated or LMA inserted or FOI performed
depending on the airway management plan.
If inhalational induction is impossible, small doses of IV induction
agent should be given to induce loss of consciousness but still
preserving spontaneous ventilation. Propofol 0.5-1mg.kg-1 or ketamine
0.5-1mg.kg-1 should be given and titrated to effect.
If inhalational induction is not possible due to pain, for instance, from
an infected facial mass/tumour (rather than because of a large extraoral
tumour meaning a face mask will not fit), give a small dose of ketamine,
then apply the face mask and deepen anaesthesia by spontaneous
inhalation with sevoflurane or halothane. In our experience, this
combination provides better conditions for laryngoscopy than when
using intravenous ketamine alone.
Nasal fibreoptic intubation – general
• Maintain anaesthesia either with incremental doses of ketamine
or inhalational anaesthesia either via a nasal airway in the other
nostril connected to the breathing circuit or using a specially
designed facemask with a port for insertion of the fibreoptic
bronchoscope.
Table 3. Size compatibility of tracheal tubes, bronchoscopes and LMAs
Tracheal tube size 2.5 3.0 3.5 4 4.5 5 6
Will fit through classic LMA size: 1 1 1.5 2 2 2.5 3
Will fit over bronchoscope Outer Diameter: 2.0mm 2.5mm 2.8mm 3.5mm 3.5mm 4.1mm 5mm
Will fit over AEC size: 7F 8F 8F 11F 11F 11F 14F
[Note: different brands of LMA vary in their internal diameter. It is important to determine the compatibility of equipment within your own department.]
• Use a topical vasoconstrictor to prevent bleeding from the nose
during FOI, as otherwise this may make intubation impossible.
Pseudoephedrine, ephedrine, phenylephrine, oxymetazoline, or
nasal packs soaked in 1:10,000 adrenaline may be used, depending
on local availability.
• Apply topical lidocaine to the nose and oropharynx. Larger
fibreoptic laryngoscopes often have a channel through which local
anaesthesia can be injected. Alternatively an epidural catheter can
be passed through the suction port (if present) and local anaesthetic
injected through this. Be careful not to exceed the maximum dose
of lidocaine (3mg.kg-1 i.e. 0.3ml.kg-1 of a 1% solution).
The correct size of tracheal tube is critical to success. Too large a
tube will fail and require the bronchoscope to be withdrawn and the
procedure repeated. Too small may make subsequent positive pressure
ventilation difficult. It is sensible to use a small cuffed tube if available,
rather than repeated bronchoscopy.
Fibreoptic intubation through an LMA
There are three main techniques available:
1. Railroad the tracheal tube over the fibreoptic bronchoscope into
the trachea
2. Railroad an airway exchange catheter (AEC) over the bronchoscope
into the trachea.
3. Pass a soft tip wire through the suction channel of the bronchoscope
into the trachea, then pass an AEC or similar over the wire as a
guide for the tracheal tube.
The choice of technique depends upon size of the child, the size of the
LMA, and the diameter of available bronchoscope (Table 3). Removal
of the LMA once the tracheal tube is in situ may be challenging.
Options include:
• Leave the LMA in situ
• Use a long tracheal tube (croup tube)
• Fix two tracheal tubes together over the FOB; the LMA may be
withdrawn over the tracheal tubes.
• Use an AEC.
Tracheostomy
A tracheostomy should be performed by an experienced practitioner,
normally an ENT surgeon. Inhalational anaesthesia or small
incremental doses of ketamine (as above) may be given to supplement
local infiltration anaesthesia. The child should breathe 100% oxygen
by facemask.
DIFFICULT AIRWAY CART
The equipment available in different institutions will vary considerably.
It is good practice to organise airway equipment in such a way that
it is readily accessible in an emergency. Many hospitals use a ‘difficult
airway cart’ to do this. This is simply a trolley or cart where all the
useful equipment for managing difficult airways is stored according
to the step-wise approach to managing a difficult airway.
For example, using the algorithms presented in this review, the difficult
airway cart could consist of a series of drawers or boxes containing:
Drawer 1: simple laryngoscopes and airway adjuncts.
Drawer 2: alternative laryngoscopes and LMAs.
Drawer 3: equipment for fibreoptic intubation
Drawer 4: equipment for CICV situations.
Whatever the availability and variety of equipment, the difficult airway
cart (or boxes) should always be stored in the same place, close to the
operating rooms, and the contents regularly checked. The cart should
be physically present in the operating room for any child with an
anticipated difficult airway; and can be quickly fetched when faced
with an unexpected problem.
CONCL USION
Unexpected difficult airways in paediatric practice are rare. Many
problems can be prevented by routine pre-operative airway assessment,
pre-oxygenation, and preparation of equipment. A simple step-wise
approach to management improves outcome. Anaesthetists have
a responsibility to be familiar with airway algorithms and make
pragmatic modifications to account for available resources.


== REFERENCES ==
== REFERENCES ==
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