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:
  1. Problems with oxygenation/circulation
  2. Problems with inadequate sedation/topicalisation
  3. Problems with visibility of relevant structures
  4. Problems with tube advancement
  5. 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