#33 Anatomically Difficult Airway Part 1

On this week’s episode of Critical Care Time, Nick & Cyrus return to talk about airway management in the ICU. In season 1 we focused on the physiologically difficult airway. Now we will begin to unravel the anatomically difficult airway. Today we will break things down by covering foundational concepts, discussing some of the physical and cognitive tools you can use to address an airway, and basically set the stage for part II where we will go through some case studies and leave you with our pitfall and pearls for anatomically difficult airways. This episode is packed with clinical pearls that will empower you to take on even the spiciest of airways!As always - give us a watch or a listen and let us know what you think! Don’t forget those reviews!!

Show Notes:

What is an anatomically difficult airway?

  • An anatomically difficult airway is a situation where a skilled operator faces difficulty intubating a patient due to physical challenges with preparation, visualization, or passing the tube through the vocal cords.

    • Success is dependent on overcoming the physical/technical barriers presented.

    • Contributors to an anatomically difficult airway may include:

      • Facial hair

      • Redundant skin/soft tissue from the neck, up

      • Small mouth

      • False, loose, missing teeth 

      • Poor neck mobility (patients with RA, prior neck surgery)

      • Prior neck surgery/radiation (ex: prior/remote tracheostomy)

      • Known H/N cancer

      • Recent/prior neck/facial trauma

      • Bleeding & vomitous (makes visualization challenging)

      • Short neck and/or anterior airway

      • Oral infections/abscesses

      • Vocal cord edema

      • …and more!

  • This is in contrast to a physiologically difficult airway, where the patient's disease state(s) contribute to hemodynamic instability which makes the peri-intubation period challenging and potentially life threatening.

    • Success is dependent on overcoming the patient-specific disease factors that make for a challenging airway (mitigating shock, resuscitation & pre-resuscitation, etc.)

  • An airway can (of course!) be both anatomically & physiologically challenging.

  • According to a meta-analysis of over 50,000 patients, difficult airways have a prevalence of about 5.8% of all intubations.


Anticipating the Anatomically Difficult Airway

  • Frank Borman: “A superior pilot uses his superior judgment to avoid situations which require the use of his superior skill.”

    • So: “A superior intensivist uses their superior judgment to avoid the difficult airways that would require the use of superior skill.”

  • Tools to predict difficult airways:

    • MOANS (difficult to BVM/bag)

    • LEMON (difficult to intubate)

    • RODS (difficult to place SGA)

    • SHORT (difficult eFONA - emergency front-of-neck airway)

  • MOANS

    • Mask seal

    • Obesity/obstruction

    • Age>55

    • NO teeth

    • Sleep apnea / stiff lungs

  • LEMON

    • Look at head/neck

    • Evaluate (3-3-2) rule

      • Interincisor distance (IID): More than 3 fingers between the open incisors, indicating patient's mouth opens adequately to permit the laryngoscope to reach the airway

      • Hyoid-mental distance (HMD): more than 3 fingers along from mentum to hyoid bone, which indicates enough space for intubation

      • Hyoid-thyroid cartilage distance (HTD): More than 2 fingers from hyoid to thyroid cartilage.

    • Mallampati Score

      • Class 0: Any part of the epiglottis is visible

      • Class I: soft palate, uvula, and pillars are visible

      • Class II: soft palate and uvula are visible

      • Class III: only the soft palate and base of the uvula are visible

      • Class IV: only the hard palate is visible

    • Obstruction

    • Neck Mobility

  • RODS

    • Restricted mouth opening 

    • Airway obstruction

    • Distorted airway

    • Stiff lungs / surgical spine

  • SHORT

    • Surgery (H&N)

    • Hematoma

    • Obese

    • Radiation

    • Tumor

Planning for the Anatomically Difficult Airway 

  • This is the time for your best operator to either take the airway OR be immediately available to take over if indicated.

  • Clearly assign roles.

  • Talk through the plan/pre-plan:

    • “First attempt will be XXX, followed by YYY, if we proceed to ZZZ I expect 1, 2 and 3 to occur simultaneously without me needing to ask.”

  • Closed loop communication:

    • Physician: “If I call for the cric kit, Michael. I need you to STAT page anesthesia & general surgery to the bedside for a CODE AIRWAY.”

    • Michael: “If you call for the cric kit I’ll call anesthesia and general surgery to the bedside, STAT.” 

  • Effective preoxygenation:

    • Why? Essentially you are increasing the O2 concentration in the airway & lungs by 5-fold assuming the patient was on RA and you are providing 100% oxygen.

    • Strategies:

      • BVM

      • NIPPV (PREOXI)

      • High-Flow 

      • Apneic oxygenation?

        • Providing oxygen when the patient is apneic (i.e. paralyzed) through passive/semi-passive oxygenation that allows for nitrogen washout.

        • Limited data to support, makes sense physiologically, won’t hurt the patient but don’t delay intubation to provide apneic oxygenation.

  • Where should the intubation occur?

    • ED? ICU? Ward? OR?

  • Positioning:

    • Bending/elevating the head of the neck only can actually occlude the airway

    • Consider the “sniffing” position or reverse trendelenburg - whole bed is positioned at an angled-down, continuous slope with the feet below the head 

  • Awake vs Asleep:

    • May want to maintain airway reflexes if the airway is likely to be difficult.

    • Consider the awake bronchoscopic intubation and pre-treating with lidocaine, benzocaine and cocaine in certain cases.

    • For topicalization, consider nebulization and/or atomization. 

    • Remember: For lidocaine NOT blended with any other medications (i.e. lidocaine WITHOUT epi) you want to keep the total dose at < ~5mg/kg to avoid toxicity.

    • Ketamine can be a useful drug to cause some degree of dissociation without impairing the respiratory drive. Can give in smaller, repeated doses until the effect is achieved.

  • Using paralysis - what are the options:

    • No-paralytic and just sedation (generally not advisable due to reflexes making intubation difficult / worse outcomes)

    • Rapid-sequence intubation (sedative and paralytic essentially given at the same time)

    • Delayed sequence intubation (sedative given, flushed, wait for effect, optimized oxygenation, then paralytic, flush and go).

  • Final planning considerations

    • Nasotracheal intubation

      • Consider in trauma situations

      • Recommend back-up at the bedside - these are not common procedures

      • A regular 5-0 ETT can be used, typically threaded over a bronchoscope

      • Topicalize, topicalize, topicalize!!!!! Consider cocaine or Afrin to minimize bleeding / vasoconstrict prior to attempting.

    • VL vs DL

    • Bronchoscope?

      • Whether or not a nasotracheal intubation is on the table, consider having a disposable bronchoscope at the bedside for anticipated difficult airways.

      • Think of it as a “smart bougie.”

    • Bougies?

      • They can be helpful, however, not supported by the 2021 JAMA trial, appropriately named the BOUGIE trial

      • Reasonable to have one in the room, to practice with one, but if you are comfortable with a bronchoscope that provides similar benefits with the huge-add of optics!

    • eFONA:

      • Make sure you have the tools (Circ-Kit, etc.) and the experienced operators at the bedside or readily available if you think you are going to need to “cut the neck”.

      • Another good argument for actual simulation / cognitive simulation!

    • Suction: 2 is 1 and 1 is none when it comes to difficult airways 2/2 contamination! 

      • The thicker/shorter/stockier the suction device, the better the suction!

      • Remember: Pousille’s law!!!

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#34 Anatomically Difficult Airway Part 2

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#32 Three Wishes with Dr. Thanh Neville