Module 12
The American Society of Anesthesiologists'
Management
of the Difficult Airway Algorithm
and Explanation-Analysis of the Algorithm
The ASA Algorithm on the
Management of the Difficult Airway
AWAKE TRACHEAL INTUBATION
Although awake intubation is generally
more time consuming for the anesthesiologist and a more
unpleasant experience for the patient, there are several
compelling reasons why intubation should be done while a patient
with a recognized difficult airway is still awake. First,
and most important, the natural airway will be better maintained
in most patients when they are awake (“no bridges are burned”).
Second, in the awake patient, enough muscle tone is maintained
to keep the relevant upper airway structures (the base of the
tongue, vallecula, epiglottis, larynx, esophagus, and posterior
pharyngeal wall) separated from one another and much easier to
identify. In the anesthetized and paralyzed patient, loss
of muscle tone tends to cause these structures to collapse
toward one another (e.g., the tongue moves posteriorly), which
distorts the anatomy.29,48
Third, the larynx moves to a more anterior position with the
induction of anesthesia and paralysis, which makes conventional
intubation more difficult.49
Thus, if a difficult intubation is anticipated, awake
endotracheal intubation is indicated.
Crucial to the success of an awake
endotracheal intubation is proper preparation of the patient
(see Chapter 10). Most
intubation techniques will work well in patients when they are
quiet and cooperative and have a larynx that is nonreactive to
physical stimuli. The components of proper preparation for
an awake intubation consist of psychological preparation (awake
intubation will proceed more easily in the patient who knows and
agrees with what is going to happen); appropriate monitoring
(electrocardiogram, noninvasive blood pressure, pulse oximetry,
and capnography); oxygen supplementation (nasal prongs, nasal
cannula, suction channel of a fiberoptic bronchoscope (FOB),
transtracheal catheter),5,7,23,42
vasoconstriction of the nasal mucous membranes, (if performing
nasal intubation) administration of a drying agent and topical
anesthesia; judicious sedation (keeping the patient in
meaningful contact with the environment); performance of
laryngeal nerve blocks (e.g., block lingual branch of the
glossopharyngeal nerve and the superior laryngeal nerve);
aspiration prevention (see Chapter
11); and having the appropriate
airway equipment available. Box 2 lists the suggested (ASA
guidelines) contents of a portable airway management cart.47
BOX 2 Suggested contents of
the portable storage unit for difficult airway management
IMPORTANT: The items listed in
this box represent suggestions. The contents of the portable
storage unit should be customized to meet the specific
needs, preferences, and skills of the practitioner and
healthcare facility.
1. Rigid laryngoscope
blades of alternate design and size from those routinely
used; this may include a rigid fiberoptic laryngoscope
2. Endotracheal tubes of
assorted sizes
3. Endotracheal tube
guides. Examples include (but are not limited to) semirigid
stylets, ventilating tube changer, light wands, and forceps
designed to manipulate the distal portion of the
endotracheal tube
4. Laryngeal mask airways
of assorted sizes; this may include the intubation laryngeal
mask airway (LMA Fastrach™) and the LMA-Proseal™ (LMA North
America, Inc. San Diego, CA)
5. Fiberoptic intubation
equipment
6. Retrograde intubation
equipment
7. At least one device
suitable for emergency nonsurgical airway ventilation.
Examples include (but are not limited to) the Esophageal
Tracheal Combitube (Tyco Healthcare, Mansfield, MA), a
hollow jet ventilation stylet, and a transtracheal jet
ventilator
8. Equipment suitable for
emergency surgical airway access (e.g., cricothyrotomy)
9. An exhaled CO2
detector
10. Rigid ventilating bronchoscope
There are numerous ways to intubate the
trachea and/or ventilate a patient
(see Chapters 13-30). Box 3
shows a list of the techniques contained within the ASA
guidelines. The techniques chosen will depend, in part,
upon the anticipated surgery, the condition of the patient, and
the skills and preferences of the anesthesiologist.
BOX 3 Techniques for difficult
airway management
IMPORTANT: This box displays
commonly cited techniques. It is not a comprehensive list.
The order of presentation is alphabetical and does not imply
preference for a given technique or sequence of use.
Combinations of techniques may be employed. The techniques
chosen by the practitioner in a particular case will depend
upon specific needs, preferences, skills, and clinical
constraints.
I. Techniques for
difficult intubation
Alternative laryngoscope blades
Awake intubation
Blind intubation (oral or nasal)
Fiberoptic intubation
Intubating stylet or tube changer
Invasive airway access
Laryngeal mask airway as an intubating
conduit
Lightwand
Retrograde intubation
II. Techniques for
difficult ventilation
Esophageal tracheal combitube
Intratracheal jet stylet
Invasive airway access
Laryngeal mask airway
Oral and nasopharyngeal airways
Rigid ventilating bronchoscope
Transtracheal jet ventilation
Two-person mask ventilation
Occasionally, awake intubation may fail
owing to a lack of patient cooperation, equipment or operator
limitations, or all of these. Depending on the precise cause of
failure of awake intubation: 1) the surgery may be canceled (the
patient needs further counseling, airway edema, or trauma has
resulted, or different equipment or personnel is necessary); 2)
general anesthesia (GA) may be induced (the fundamental problem
must be considered to be a lack of cooperation, and mask
ventilation considered to be nonproblematic); 3) regional
anesthesia may be considered (requires careful clinical judgment
balancing risks and benefits) (see
Chapter 42); or 4) a surgical
airway may be created (the surgery is essential and GA is
considered inappropriate until intubation is accomplished.
Occasionally, a surgical airway is the best choice for
intubation (e.g., with laryngeal or tracheal fracture or
disruption, upper airway abscess, combined mandibular-maxillary
fractures)
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