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Anaesthesiology
The Difficult Airway Algorithm and Infographics
Built from Barash Clinical Anesthesia, 9th Edition
What’s inside
15 sections · 186 slides
Overview
- Scope of this presentation
- Core vocabulary used throughout
- Rationale for the algorithm and its pre-2022 revisions
The ASA Difficult Airway Algorithm
- History of the ASA algorithm
- What the 2022 revision added
- The guideline's own framing of the problem
- ASA Difficult Airway Algorithm for adult patients
- Reading the algorithm figure
- Structure of the adult infographic
- Difficult airway infographic for adult patients
- Pre-airway management decision making tool
- Awake airway management pathway
- Airway management with induction of anaesthesia
Choosing awake or after induction
- Purpose and inputs of the decision tree tool
- Sequence of the decision tree
- First two questions: laryngoscopy and ventilation
- Third and fourth questions: aspiration and desaturation
- The uncooperative patient exception
- Options when awake intubation fails
- Regional anaesthesia as an escape route
- Regional anaesthesia for patients with likely difficult airways
- Reading the regional anaesthesia table
The unanticipated difficult airway
- The unanticipated difficult airway
- Review of airway management strategy prior to anaesthetic induction
- Airway strategy review before induction
- Optimisation of oxygenation throughout airway management
- Preoxygenation and continued oxygenation
- Broadened meaning of induction in 2022
- Judging whether the airway plan succeeded
- End-tidal carbon dioxide as the patency signal
- Carbon dioxide versus oxygen saturation
- The non-emergency pathway
- Three subpaths of the non-emergency pathway
- Limiting the number of attempts
- The emergency pathway and the principle of constraint
- Trigger for the emergency invasive airway pathway
- Modalities in the emergency invasive airway pathway
- Role of rigid bronchoscopy and ECMO
Awake airway management
- Rationale for the awake technique
- Advantages of the awake state
- Cautions and contraindications to awake intubation
- Neurological testing and patient preparation
- Principles of sedation for awake intubation
- Sedative agents used for awake intubation
- Dexmedetomidine for awake intubation
- Dexmedetomidine side effects, and the limit of sedation
- Antisialagogues: purpose, drugs and timing
- Nasal vasoconstriction, aspiration prophylaxis and oxygen
Anaesthetising the airway
- Why the airway needs local anaesthesia
- Systemic absorption of airway local anaesthetics
- Blood levels after topical versus nebulised lidocaine
- Lidocaine for airway topicalisation
- Benzocaine: properties, dosing and methaemoglobinaemia
- Three target areas for airway anaesthesia
- Airway innervation
- Preparing the nose, and its nerve supply
- Invasive palatine nerve block via the oral route
- Non-invasive nasal nerve blocks
- Nerve supply and simple techniques for the oropharynx
- The glossopharyngeal nerve and why it is blocked
- The palatoglossal arch as a block landmark
- Injected glossopharyngeal block: technique and drawbacks
- The superior laryngeal nerve and its branches
- Non-invasive superior laryngeal nerve block
- Invasive superior laryngeal nerve block
- Translaryngeal injection for the cords and trachea
- Confirming entry and managing the cough
- Topicalisation through the flexible scope
Preoperative endoscopic airway evaluation
- Clinical scenario: preoperative endoscopy
- Concept of preoperative endoscopic airway evaluation
- Study evidence for preoperative endoscopic evaluation
- Three questions asked during the examination
- Practicalities and wider uses of the examination
The flexible intubation scope
- Clinical scenario: flexible scope intubation
- Origins of flexible scope intubation
- Why the flexible scope remains unique
- Clinical situations favouring flexible scope intubation
- Diagnostic and therapeutic uses below the cords
- Endoscopic views below the vocal ligaments
- Laryngeal web seen at endoscopy
- Tracheal mass seen at endoscopy
- Skill maintenance through routine use
- Contraindications to flexible scope intubation
- Contraindications and the problem of secretions
- Other practical constraints
- Common reasons for failure of flexible scope intubation
- Themes among the failure modes
- Awake use of other intubating devices
Anatomy of the flexible intubation scope
- From fibreoptics to video chips
- Single-use flexible intubation scope components
- The accessory lumen or working channel
- Tip articulation and rotational control
- Light sources in flexible scopes
- Supporting equipment for flexible scope intubation
Using the flexible intubation scope
- Holding and steering the scope
- Loading the tube and choosing scope diameter
- Hang-up: definition, frequency and the fix
- Size discrepancy between tube and scope
- Tube design and other measures against hang-up
- Choosing and preparing the nasal route
- Purpose of intubating oral airways
- Intubating oral airways
- Features of the Ovassapian airway
- Features of the Williams and Berman airways
- Managing glottic closure, gag or cough
- Advancing the tube and confirming its position
- Flexible scope-aided intubation techniques
- Themes among the scope-aided variations
Rescue with the supraglottic airway
- Clinical scenario: failed rapid-sequence induction
- Rescue and definitive intubation in the case
- Frequency of combined mask and laryngoscopy failure
- Why supraglottic airways rescue so well
- Aspiration risk with supraglottic airways
- Evidence base for supraglottic rescue
Flexibility and back-up planning
- Clinical scenario: trauma with declining consciousness
- Course and outcome of the trauma case
- Neuromuscular blockade and laryngoscopy
- Neuromuscular blockade and facemask ventilation
- Lessons from abandoning the original plan
Other airway devices
- Oesophageal tubes with laryngeal openings
- Oesophageal tracheal tube with laryngeal ports
- Prehospital role of oesophageal tubes
- Airway introducers
- Emergency department evidence for the bougie
- The Eschmann introducer
- The Frova intubating introducer
Front-of-neck access
- Indication for transcricothyroid membrane procedures
- Criteria for performing emergent invasive airway management
- Interpreting the emergent invasive airway criteria
- Principle of retrograde wire-aided intubation
- Equipment for retrograde wire intubation
- Notes on the retrograde intubation equipment
- Indications for retrograde wire intubation
- Contraindications and complications of retrograde intubation
- Definition and anatomy of cricothyrotomy
- Elective use and contraindications of cricothyrotomy
- Percutaneous emergency airway access
- Three techniques of percutaneous emergency airway access
- Success rates of front-of-neck techniques
- Improvised versus purpose-built equipment
- Identifying the cricothyroid membrane
- Positioning and preparation for invasive access
- Needle insertion and the air-contrast technique
- High-pressure oxygen source for transtracheal ventilation
- Settings for transtracheal jet ventilation
- Why low-pressure systems fail
- The requirement for a route of gas escape
- Low-flow oxygen systems and flow interruption
- The Enk flow modulator
- Expiratory ventilatory assistance and the Ventrain
- Animal model comparison of Ventrain and jet ventilation
- Interpreting the animal model results
- Devices for percutaneous emergency airway access
- Specialised percutaneous cricothyrotomy systems
- Melker set insertion technique
- Practical points during Melker insertion
- Barotrauma complications and their causes
- Steps of the scalpel-bougie-tube technique
- The scalpel-bougie-tube technique
Conclusions
- Airway management as a core duty, and the limits of guidelines
- Evolution of technology and the breadth of skill needed
- The governing principle
- Key numbers from this topic
- Take-home points
- References
- References (continued)
- References (continued)
- References (continued)
- References (continued)
- References (continued)
- References (continued)
- Barash, Cullen, and Stoelting's Clinical Anesthesia, 9th Edition