DISCUSSION
Guidelines for the management of known difficult airways1, 6 and for intubation in critically ill
adults 7 have been published.
In known difficult airways ATI is still considered the standard
approach.1, 2, 6, 8 The benefits of ATI are, that
spontaneous breathing is preserved (hence oxygenation), that the patient
can be sitting up (thus providing maximal airway diameter and avoiding
atelectasis) and that there is some protection against aspiration
(preserved reflexes and muscle tone).2, 6, 8Traditionally, ATI is performed with a FB.1, 2, 6, 8
The VL revolutionised airway management, since even previously difficult
airways only manageable with the FB now often were manageable with the
VL. Accordingly, awake airway techniques and FB intubation skills in
particular may have become less frequently needed/practiced by the
typical anaesthesiologist and are underutilised
techniques.9 Prior to the widespread adoption of VL´s,
only approximately 50% of anaesthesiologists considered themselves to
be skilled in FB intubation.10 Reluctance to perform
ATI-FB may be because of lack of training and concerns related to time
delay and patient discomfort.6, 8, 9 With the right
preparations though, the time spent on the procedure is acceptable2, 11, 12 and most patients do not experience
discomfort.2, 11, 13, 14
If ATI-FB, performed by a non-expert anaesthesiologist is required,
considerations should be made early before the patient´s
physiological status has deteriorated. The cricothyroid membrane should
be identified (if necessary guided by ultrasound) and marked in advance
in the extended-neck position.2, 15 The patient should
be positioned upright sitting and face-to-face with the
anaesthesiologist, providing both maximal luminal patency and maximal
patient comfort and, hence, a reduced need for
sedation.3, 4, 6
The most common problems with acute ATI-FB in critically ill patients
may be categorized as follows:
- Problems with oxygenation/circulation
- Problems with inadequate sedation/topicalisation
- Problems with visibility of relevant structures
- Problems with tube advancement
- Impossible FB intubation necessitating a backup strategy
Preoxygenation can be achieved using NIV with 100% oxygen while
performing sedation/topicalization 7, NIV can be
changed to HFNO at 100% oxygen and maximal flow, for the intubation
itself. The patient should be fully monitored, including a-line and
large bore venous line (if time permits central venous line) and
vasopressors/inotropes should be ready and used
proactively.7
In the elective ATI-FB, no superior sedation/topicalisation regime has
been identified.8 In the critically ill, a non-opioid
based regime could theoretically provide a safety benefit and minimal
sedation should be titrated cautiously. Over-sedation would be dangerous
due to the risk of secondary airway obstruction,
hypoventilation/hypoxia, and circulatory collapse.6, 8Optimal airway topicalisation is the key to success.2,
6, 8 Oral intubation is preferred to avoid epistaxis2, and to employ a sufficiently large tube size, if a
period of ventilator therapy is expected. As last resort plans, the
nasal route is prepared from the start (backup if oral route access
fails) and subcutaneous local anaesthetics can be placed superficially
to the cricothyroid membrane (backup if invasive techniques have to be
performed). The maximal dose of topical lidocaine is 9
mg/kg.1, 6
The visibility of relevant structures is enhanced if the upper airway
diameter is enlarged, secretions and blood do not obscure the vision
with the FB, and the glottis and vocal cords can be identified
expediently. Simple maneuvers can contribute to this (Fig. 1). The
upright sitting position has the most significant impact on airway
patency.6 Specialized oral airways for FB´s (e.g.
Berman), increase the upper airway diameter, but insertion might be
impossible in cases of severely limited mouth opening. If the patient´s
cerebral status deteriorates (or due to over-sedation), biting on the FB
or tube may make oral intubation impossible. Insertion of an oral
airway, bite block, or a HA-VL blade intraorally as conduit for the FB
may alleviate this problem (otherwise the nasal route can be
considered). Thick purulent secretions can cover the mucosal surfaces
thus acting as a mechanical barrier for optimal topicalisation of these
areas and can hinder visualisation with the FB. Cautious suctioning
should thus be performed before topicalisation. Early administration of
an antisialologue (e.g., glycopyrrolate), has a mucosal drying effect
and vasoconstrictor agents applied to the mucosa (especially nasally)
can minimise epistaxis.6 Retrograde light-guided
laryngoscopy is not a new idea; a method with direct laryngoscopy and a
flashlight held on the front of the neck has previously been
published.16, 17 When IRRIS is placed superficial to
the patient´s cricothyroid membrane or trachea, it emits flashing
infrared light through the skin.5 When a FB is
introduced into the airway, the infrared light will become visible as a
flashing white light on the FB´s video-screen, showing the pathway to
the vocal cords and trachea.5 IRRIS has been shown
beneficial in the elective VL-guided intubation of lean respectively
extreme obese patients 18, 19, elective ATI-FB in
known difficult airways 20 and in ATI-FB of an
obstetric patient with a known difficult airway 4.
The incidence of tube impingement is reduced, if specialized tubes are
used (e.g., LMA®Fastrach™ ETT, Teleflex,
Beaconsfield, UK), the opening of
the bevel is oriented posteriorly and the gap between the tube and the
FB is minimised.6
In hospitals with ear, nose and throat (ENT) surgical
expertise, awake surgical tracheostom y would have been a viable
backup option and could also have represented the primary
plan.2, 3 In hospitals without ENT surgical
backup as in this case, immediate relocation of the patient with NIV to
another hospital can be considered, if the clinical status is expected
to be very stable for the duration of the transport. If acute
ATI-FB is attempted and fails, awake cricothyroidotomy (by an
anaesthesiologist) or awake percutaneous dilatational
tracheostomy (by an experienced intensivist) can be
considered.3 Emergency cricothyroidotomy after
high-risk general anaesthesia with full relaxation should remain the
last resort, since failure rates may be over 50% when performed by an
anaesthesiologist in a ´cannot-intubate-cannot-oxygenate´
situation.9, 11