J R Soc Med 2001;94:341-344
© 2001 Royal Society of Medicine
Management of the difficult airway in children
Robert W M Walker FRCA
Royal Manchester Children's Hospital, Pendlebury, Manchester M27 4HA,
UK
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INTRODUCTION
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Airway management and endotracheal intubation in children usually
present
no difficulties for the experienced anaesthetist. In
infants, access may be
slightly more problematic because of
certain anatomical variations: the tongue
is large relative
to the mandible and the larynx is more cephalad than in the
older
child. In infants below the age of four months the epiglottis
is at the
level of the first cervical vertebra; at six months
it has moved down to the
level of the third cervical vertebra.
Unlike the epiglottis in adults, the
epiglottis in infants is
hard and narrow and is folded into an inverted U
shape. These
features together give rise to what many people refer to as
the
‘anterior larynx’, but in fact are just due
to the relative
macroglossia and the higher placement of the
larynx. The anatomical variations
between infants, children
and adults should be easily overcome by use of
straight-bladed
laryngoscopes which can pick up the epiglottis and reveal the
larynx.
The children who present major difficulties for the anaesthetist are not
easily missed. In this paper I focus on congenital causes. Others are
retropharyngeal abscess, burns, trauma and Still's disease.
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PATIENT CHARACTERISTICS
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Common craniofacial abnormalities are the Pierre Robin sequence
and
Treacher Collins and Goldenhar syndromes, but many do not
have an eponym.
The Pierre Robin sequence consists of micrognathia and relative
macroglossia with or without cleft palate. In the severe case, airway
obstruction develops in the first four weeks of life. When the baby is supine
the nasopharynx will fill with the tongue (via the cleft palate if present)
and cause varying degrees of airway obstruction. Matters become worse if the
child struggles and generates a greater negative intrathoracic pressure. These
children are best nursed prone, but a tracheostomy may prove necessary. To the
anaesthetist the combination of severe micrognathia and relative macroglossia
and the cephalad placement of the larynx can make the larynx almost invisible
with conventional equipment.
The Treacher Collins syndrome (mandibulofacial dysostosis) consists of
abnormalities of the external, middle and inner ear causing hearing loss,
mandibular deformities and minor eye abnormalities. Sometimes the facial bones
are hypoplastic (usually the zygoma and mandible). These children may also
have macrostomia, with or without a cleft or high arched palate, and abnormal
dentition. The Goldenhar syndrome (oculoauriculovertebral dysplasia) consists
of eye anomalies and ear defects which may again result in hearing loss. Many
children with this syndrome have micrognathia and a cleft palate, and there
may be unilateral mandibular hypoplasia. In addition, 40% have vertebral
anomalies in the form of a Klippel—Feil anomaly. Both these craniofacial
syndromes present major airway difficulties similar to the Pierre Robin
sequence, and in children with Goldenhar syndrome and associated
Klippel—Feil anomaly there is the added problem of a short immobile
neck1,2.
The mucopolysaccharidoses (such as Hurler's, Hunter's and
Marateaux—Lamy syndromes) are hereditary progressive disorders in which
deficiency of an enzyme results in excessive intralysosomal accumulation of
glycosaminoglycans (mucopolysaccharides). The effects make anaesthesia and
airway management extremely
hazardous3,4.
These patients develop progressive generalized infiltration and thickening of
the soft tissues. The oropharynx becomes obstructed by a large tongue with or
without tonsillar hypertrophy. The nasal airway becomes progressively narrowed
by thickening of the mucous membranes, adenoidal hypertrophy and redundant
‘granulomatous’ tissue. The neck is typically short and immobile
and the temporomandibular joints may be involved; sometimes the cervical spine
is unstable. The supraglottic and infraglottic regions thicken progressively
and thus intubation becomes more difficult with age. The age when children
with different types of mucopolysaccharidoses become difficult to manage
varies greatly and thee is variation within each syndrome category. In
general, children with Hurler's, Hunter's and Marateaux—Lamy syndromes
present the major challenge. A child with Hurler's syndrome may prove
difficult or impossible to intubate from as early as two years of age. These
syndromes are all progressive and the patients who reach adult life (e.g.
those with Hurler—Scheie or Morquio syndrome) will present a severe
challenge to the anaesthetist.
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ANAESTHETIC APPROACH
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Anaesthetic management of children with any of the above conditions
should
always include a full and frank discussion of risks with
parents (and child if
appropriate). The possibility of tracheostomy
and, indeed, of failure to
secure the airway should always be
mentioned.
In adult anaesthetic practice an awake technique will often be employed,
but this cannot be done in children since cooperation is required to gain good
bronchoscopic views. What are the essential components of the general
anaesthetic approach in children? Atropine premedication should be
administered to dry up secretions, then oxygen should be given with either
halothane or sevoflurane, by a spontaneously breathing method. Muscle
relaxants should be withheld until the airway is secure. Intubation should be
performed under deep inhalational anaesthesia. Use of a muscle relaxant during
induction of anaesthesia may result in a situation where the anaesthetist can
neither manually inflate the patient's lungs nor intubate, and must therefore
gain a surgical airway rapidly. Maintenance of spontaneous breathing allows
the anaesthetist a way out should the airway prove impossible to secure.
After inhalational induction of anaesthesia, the aim is to attain
anaesthesia deep enough to allow visualization of the larynx with a
laryngoscope. Should this prove not possible for whatever reason, the
anaesthetist must have a plan of how to proceed. This may be to abandon the
procedure if the surgical need is not pressing, but if the procedure is
essential then alternative means must be available to aid endotracheal
intubation. In these groups of patients, although certain manoeuvres using
conventional equipment can sometimes succeed, fibreoptic intubation techniques
are often necessary.
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FIBREOPTIC BRONCHOSCOPES USED IN PAEDIATRIC PRACTICE
(Figure 1)
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Adult bronchoscopes
Adult fibreoptic bronchoscopes (e.g. Olympus LF2) have an outer
diameter of
around 3.5-4.0 mm and thus can take realistically
a size 4.0-4.5 endotracheal
tube loaded onto them. This limits
their use in patients less than one year of
age, should a simple
railroading technique be employed, but the advantage of
these
scopes is that they have a suction channel to clear troublesome
secretions.
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Figure 1. Fibreoptic bronchoscopes used in paediatric anaesthetic practice.
The larger scope is the Olympus LF2 and is placed beside a 4.5 endotracheal
tube. The thinner scope is the Olympus LF-P and is placed beside a size 2.5
tube
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Ultrathin bronchoscopes—Olympus LF-P
Ultrathin fibrescopes (such as Olympus LF-P) have an outer diameter of
roughly 2.2 mm so a 2.5 mm endotracheal tube can be railroaded over them. The
optical quality of these scopes is superb but it should be noted that the LF-P
has no suction channel and secretions must be aspirated with a normal suction
catheter. The LF-P can be more difficult to control than the larger
bronchoscopes and much practice is required if it is to be used for difficult
intubations. It is also a delicate piece of equipment, easily damaged.
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FIBREOPTIC INTUBATION TECHNIQUES
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When one opts to use a fibreoptic bronchoscope for intubation,
the first
requirement is to keep the airway clear, by some means,
to allow the
anaesthetist time to visualize the larynx. Secondly,
an endotracheal tube must
be introduced into the trachea. This
may be achieved by loading the tube onto
the fibrescope and
railroading the tube into the trachea, but if the size is
wrong
the airway may be traumatized. An alternative technique employs
a
guidewire and this is discussed below. A guidewire technique
allows the
anaesthetist to use the more robust and more easily
guided adult-sized
bronchoscopes.
Nasal route
The nasal route is favoured in adult practice and can be used successfully
in children. In my own practice, the nasal route is used only if access to the
mouth is impossible. Although the angles to the larynx are said to be easier
when the scope is introduced through the nose, nasal bleeding caused by the
scope or the tube can be very troublesome, especially in patients with
mucopolysaccharidoses.
Oral route
With use of the oral route the airway can be preserved by many different
methods. Anaesthesia can be maintained via a nasal airway or via a specially
adapted facemask. The bronchoscope can then be inserted into the mouth and the
larynx visualized. The laryngeal mask airway can also be used. Use of this
device in anaesthetic practice can avoid the need for
intubation5, but
should intubation be deemed necessary it provides a superb airway, both to
maintain anaesthesia (freeing the anaesthetist's hands) and as a conduit for
the fibrescope to view the larynx. The laryngeal mask airway is applicable in
almost all paediatric patients with a difficult airway and is an excellent
tool to aid visualization of the larynx and entry to the
trachea6.
Intubation through laryngeal mask airway
For endotracheal intubation through the laryngeal mask both blind and
fibreoptic guided techniques have been described.
Blind techniques
Blind techniques are possible with either a gum elastic bougie or an
endotracheal tube7.
The published success rate varies and in my opinion these techniques should be
avoided in patients with a difficult airway, because of the risks of
trauma.
Fibreoptic guided techniques
Fibreoptic techniques depend on adaptation either of the laryngeal mask
airway (split8 or
shortened9) or of
the mode of endotracheal passage (telescoping the tube over the
fibrescope10 or a
wire technique 11).
Telescoping (Figure 2) involves
pushing the tube of choice onto a larger one which acts as a holding device
allowing the anaesthetist to remove the laryngeal mask airway and fibrescope
without accidentally pulling out the endotracheal tube. Shortening the
laryngeal mask airway and splitting are other methods to the same end allowing
the anaesthetist to advance the endotracheal tube through the laryngeal mask
airway which can then be removed without hazarding the tube. The technique
that I personally favour involves a wire
(Figure 3). The guidewire
technique allows the anaesthetist to insert a conventional adult fibreoptic
bronchoscope to gain a view of the larynx and use the suction facility
(lacking in the ultrathin bronchoscopes). The suction channel can then be
employed to facilitate passage of a long guidewire into the trachea. This
avoids the need to preload an endotracheal tube onto the fibrescope and
railroad the tube into the trachea through the laryngeal mask airway—a
difficult procedure, and even then the laryngeal mask airway must be removed
to allow proper fixation of the tube.
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Figure 2. ‘Telescoping’ of the endotracheal tubes over the fibreoptic
bronchoscope through the laryngeal mask airway
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Figure 3. Guidewire technique. An extra long J-tipped guidewire is emerging
through the suction channel of the fibrescope, which in turn has been guided
through the laryngeal mask airway into the trachea
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When the patient is breathing deeply, spontaneously, on sevoflurane or
halothane, the fibreoptic bronchoscope is introduced into the laryngeal mask
airway until a view of the cords is obtained. Lignocaine 2-3 mg/kg is sprayed
via the suction channel of the fibreoptic scope onto the cords. The fibreoptic
scope is manipulated through the cords into the trachea until the bifurcation
of the trachea is visible. A long J-tipped guidewire is then inserted via the
suction channel into the trachea and the fibreoptic scope is carefully
removed. If the child's trachea is deemed too small for the fibrescope, the
fibreoptic scope will simply sit above the cords and the guidewire is inserted
through the cords under direct vision down to the carina and beyond.
A ‘stiffening’ device is then railroaded over the guidewire
through the laryngeal mask airway. The stiffening devices are either a
ureteric dilator or a Cook airway exchange catheter. Once these are in place
the guidewire is removed and the position of either the ureteric dilator or
the airway exchange catheter is verified by capnography. Only after a
successful CO2 trace is obtained is the laryngeal mask airway
removed and a tracheal tube of appropriate size railroaded over the stiffening
device.
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CONCLUSION
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Fibreoptic intubation should not be undertaken lightly in children.
The
laryngeal mask airway not only provides a good airway in
a difficult
paediatric patient but also can be effective when
used as an aid to fibreoptic
intubation.
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REFERENCES
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Ross EDT. Treacher Collins syndrome: an anaesthetic hazard.
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Johnson CM, Sims C. Awake fibreoptic intubation via a laryngeal
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Walker RWM, Darowski M, Morris P, Wraith JE. Anaesthesia and
mucopolysaccharidoses: a review of airway problems in children.
Anaesthesia1994; 49:1078
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McKusick VA. Heritable Disorders or Connective
Tissue, 4th edn. St Louis: Mosby, 1972
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Brain AIJ. The laryngeal mask; a new concept in airway management.
Br J Anaesth1983; 55:801
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Walker RWM. The laryngeal mask airway in the difficult paediatric
airway: an assessment of positioning and use in fibreoptic intubation.
Paediatr Anaesth2000; 10:53
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Paediatr Anaesth1995; 5:129
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Darling JR, Keohane M, Murray JM. A split laryngeal mask as an aid
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intubating airway. Anaesthesia1993; 48:1079
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Goldie AS, Hudson I. Fibreoptic tracheal intubation through a
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Chadd GD, Walford AJ, Crane DL. The 3.5/4.5 modification for
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INTRODUCTION
PATIENT CHARACTERISTICS
