CRACKCast E192 – Airway

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This Episode of CRACKCast covers Rosen’s Chapter 1 – Airway. We are updating the first several episodes with 9th edition content. Enjoy!

There’s a reason that the first chapter of Rosen’s is devoted to airway. These are some of the most critical skills we need to know as emergency clinicians. This episode provides an overview of core airway knowledge and skills.

Shownotes – PDF here

[1] What are the indications for intubation?

  1. Failure to oxygenate
  2. Failure to ventilate
  3. Failure to protect the airway
  4. Predicted clinical course

[2] List the components of an airway exam.

You can use the mnemonic LEMON for an intuitive way to think through your airway exam.

  • Look externally:
    • Body Habitus (obesity or pregnancy)
    • GCS/Altered LOC
    • Combative?
    • External signs of trauma or burns?
  • Evaluate 3-3-2: Mouth opening (3 fingers), thyromental distance (3 fingers) and thyrohyoid distance (2 fingers).
    • Get the patient to extend their mandible outwards – bite upper lip with bottom teeth. (retrognathia + high riding larynx = difficulty tube!)
    • Dentition – caps, crowns, loose or missing teeth.
    • Does the patient have Dentures? Teeth in to ventilate, teeth out to intubate.
  • Mallampati score (Figure 1.3)
  • Obstruction/Obesity
    • General assessment of body habitus
    • Pregnancy is a predictor of difficulty
    • Signs of airway obstruction (The S’s – more later!)
  • Neck Mobility
    ○ C-spine precautions!

[3] What are the predictors of difficulty in the following situations: intubation, BVM, extraglottic device, surgical airway.

Intubation (LEMON) – Box 1.1

  • Look Externally
  • Evaluate 3-3-2
  • Mallampati
  • Obstruction/Obesity
  • Neck Mobility
  • Also consider Cormack Lehane grade – Higher Grade = higher difficulty!
    • Grade 1: Full view of the glottis
    • Grade 2a: Partial view of the glottis with view of arytenoids and cords
      • First pass success drops significantly from 2a to 2b.
    • Grade 2b: only the arytenoids are seen
    • Grade 3: only epiglottis seen
    • Grade 4: neither glottis nor epiglottis seen.

Bag valve mask ventilation (MOANS) – Box 1.2

  • Mask seal (beard!)
  • Obesity/OSA/obstructe
  • Age >55y
  • No Teeth
  • Stiffness (resistance to ventilation)

Extraglottic device (RODS) – Box 1.3

  • Restricted mouth opening
  • Obstructed/obesity
  • Distorted anatomy
  • Stiffness (resistance to ventilation)

Cricothyroidotomy (SMART) – Box 1.4

  • Surgery
  • Mass (abscess/hematoma)
  • Access/anatomy problems (obesity, edema)
  • Radiation
  • Tumor

[4] What are the physiologic predictors of difficulty?

The HOP Killers! 

  • Hypotension – peri-intubation hypotension can kill people – the switch to positive pressure ventilation often means the patient’s BP will drop around the time of intubation
  • Oxygenation – pre-intubation hypoxia or inadequate preoxygenation
  • pH – beware of ventilating a patient with severe metabolic acidosis (e.g., ASA overdose). Also, be aware that ventilation and pCO2 changes can impact a patient with increased ICP.

 

[5] What is rapid sequence intubation (RSI) and when is it used? List the 7 P’s of RSI.

Rapid sequence intubation = simultaneous administration of induction agent and paralytic, with no interposed bag-valve mask ventilation.
Minimizes risk of aspiration!

Seven P’s of Rapid Sequence intubation (Box 1.6)

  1. Preparation
  2. Preoxygenation
  3. Pretreatment
  4. Paralysis with Induction
  5. Positioning
  6. Placement of Tube
  7. Postintubation management

 

Preparation

We use the mnemonic “STATICS”

  1. Suction
  2. Tube
  3. Airway adjuncts (NPA/OPA/bougie/LMA)
  4. Tape (to secure airway)
  5. Introducer (Stylet)
  6. Circuit (vent) or BVM and Capnography
  7. Scope (laryngoscope)

Preoxygenation

3 minutes of 100% O2 gives you 6-8 minutes of safe apnea time in a healthy, non-obese adult (note that this changes for obese adults, critically ill adults, and kids).

Pretreatment

See box 1.5 for pretreatment agents covered by Rosen’s. Be careful with Fentanyl to avoid hypotension.

  1. Reactive airway disease: Albuterol, 2.5 mg, by nebulizer. If time does not permit albuterol nebulizer, give lidocaine 1.5 mg/kg IV (lidocaine should be considered optional as per Rosen’s, lack of convincing evidence for benefit).
  2. Cardiovascular disease: Fentanyl, 3 μg/kg, to mitigate sympathetic discharge
  3. Elevated ICP: Fentanyl, 3 μg/kg, to mitigate sympathetic discharge and subsequent rise in ICP

Positioning

Aim for “sniffing position.”

What is this?  Combination of flexion of the neck on the body and extension of the head on the neck.

Paralysis with Induction

Administration of induction agent (commonly, propofol or ketamine) and NMBA (rocuronium or succinylcholine) 45-60 seconds after.

Placement of Tube

Pass the tube under direct visualization of cords. Depth: traditional teaching of 21cm in females and 23cm in males may over/underestimate tube depth in certain patients, and a height-based approach may be more accurate.

Placement confirmed with ETCO2 persisting after 6 breaths.

Postintubation management

  1. Continuous ETCO2
  2. Mechanical Ventilation
  3. Chest radiograph
  4. Postintubation sedation and analgesia

[6] Describe an approach to the airway with no anticipated difficulty.

We just talked about this! RSI is the cornerstone of emergency airway management in the absence of predictors of difficulty! See figure 1.7 for the Rosen’s algorithm.

 

[7] Describe an approach to the airway with anticipated difficulty.

Arguably, all emergency airways are “difficult.” The emergency patient requiring airway management is very different than, say, an elective surgery patient going for general anesthesia.

This is an entire topic in itself. Again, use this podcast as a jumping off point – there are tons of good FOAM resources about this topic.

Core principle of this approach is that NMBAs should not be used unless:
○ Intubation is likely to be successful
○ Oxygenation can be maintained with BVM or EGD if the patient desaturates during the attempt
○ A “Forced to Act” scenario exists (i.e. rapid deterioration towards arrest in a patient with predictors of a difficult airway – in this case, RSI is the way to go).

See figure 1.9 for the Rosen’s algorithm.

[8] Describe an approach to the crash airway.

This is an immediate intubation attempt in a patient who is arresting or peri-arrest who is not likely respond to the unpleasant stimulus of laryngoscopy. If your first attempt fails, can consider a single dose of NMBA to aid in relaxation of the patient. See Figure 1.8.

[9] Describe an approach to the failed airway.

Defined as:

  • ≥3 intubation attempts by an experienced operator
  • SpO2 continuing to fall despite optimal use of BMV or EGD.
  • “Impossible” intubation after a single attempt- i.e. grade 4 view- and no backup devices (VL, EGD) available

Can’t Intubate, Can’t ventilate? Time for a cric!

If you are in a can’t intubate, can oxygenate situation, you have time. Call for backup and consider rescue devices.

See figure 1.10.

[10] How do you perform a surgical cricothyroidotomy?

First—The Anatomy!

Landmarks: Cricothyroid membrane is below the thyroid cartilage and above the cricoid cartilage. These 2 landmarks are palpable on most patients.

Knife-finger-bougie approach

Equipment:

  • Scalpel
  • Artery forceps
  • Bougie
  • Size 6 ETT

Technique:

  • Extend the neck to make anatomy easier to palpate (“laryngeal handshake”)
  • Stabilize thyroid cartilage with non-dominant hand.
  • Hold scalpel with dominant hand, can rest on sternum for support.
  • Make a 4cm vertical incision over cricothyroid membrane. (may extend from mandible to sternum if you can’t palpate the anatomy)
  • Palpate the cricothyroid membrane ± blunt dissect with forceps until membrane is visible.
  • Make a horizontal incision through the cricothyroid membrane.
  • Dilate with a gloved little finger
  • Pass a bougie alongside the finger into the trachea
  • Confirm bougie placement with finger (should also get holdup at the carina ± sensation of tracheal rings).
  • Pass ETT over the bougie. May need to corkscrew the ETT to advance. Advance the ETT until the cuff is no longer visible.
  • Hold the ETT in place and remove the bougie.
  • Confirm placement with ETCO2 + adjunctive measures (CXR, misting, chest rise, etc) and connect to a BVM/Vent!

[11] List common induction agents and paralytics.

This is just a quick overview!

Common Induction Agents

Etomidate

  • Imidazole derivative
  • Induction Dose: 0.3 mg/kg
  • Pros: Does not impact hemodynamics
  • Cons: Transient adrenal suppression.

Ketamine

  • Phencyclidine derivative
  • Induction dose: 1-2 mg/kg
  •  Pros:
    • Reaches clinical effect rapidly within 30 seconds, nearing peak effects at 1-minute
    • Preserves protective airway reflexes and ventilatory drive
    • Hemodynamically neutral
    • Bronchodilatory effects- beneficial in the asthmatic patient
  • Cons:
    • Laryngospasm, emergence reactions, transient apnea and respiratory depression.

Propofol

  • Alkylphenol with GABA receptor stimulation activity
  • Induction dose: 1.5 mg/kg IV
  • Pros:
    • Rapid onset of action
    • Brief duration of action
    • Diminished ICP and cerebral metabolic rate, making it ideal to use in the patient with head injuries
  • Cons:
    • Pain with injection
    • Vasodilation, myocardial suppression = hypotension!
    • Respiratory depression and apnea

Paralytics

Rocuronium

  • A competitive non-depolarizing neuromuscular blocking agent
  • RSI dosing: 1.0-1.2 mg/kg IV
  • Pros:
    • Rapid onset of action
    • No absolute contraindications to rocuronium
    • Prolonged duration of action (approximately 50 minutes); as such, can be used post-intubation in patients who require long-term paralysis
  • Cons:
    • Prolonged duration of action, which would require the intubator to bag mask ventilate a patient for quite some time if intubation fails

Succinylcholine

  • A non-competitive depolarizing neuromuscular blocking agent
  • Combination of two acetylcholine molecules
  • RSI dosing: 1.5 mg/kg
  • Pros:
    • Rapid onset of action (paralysis with 45 seconds of rapid IV administration)
    • Brief duration of action (6-10 minutes in most patients)
    • Reliably produces paralysis in most patients
    • Limited common serious side effects
  • Cons:
    • Know the contraindications!
  • Table 1.2:  Contraindicated for:
    • Burns >10% BSA
    • Crush Injury
    • Denervation Injury (CVA, SCI)
    • Neuromuscular Disease (ALS, MS, MD)
    • Intra-abdominal sepsis

WiseCracks

[1] Describe an example airway plan.

The key here is to have a clearly outlined plan that has been vocalized to the room (or to your examiner). An example airway plan for an RSI might look something like this (assuming you have gone through and gathered your equipment, chosen your induction agent/NMBA, preoxygenated the patient, etc.):

  • Plan A: Attempted direct laryngoscopy ± bougie assist
  • Plan B: Video laryngoscopy
  • Plan C: LMA and call for additional assistance
  • Plan D: if failed airway with a can’t intubate, can’t ventilate situation exists, surgical cricothyroidotomy.

Obviously, this would vary depending on the clinical situation!

[2] List maneuvers used to open the airway and maintain a patent airway.

Maneuvers that one can use to open the airway or maintain airway patency:

1. Head Tilt, Chin Lift
This strategy can be used in the patient without a suspected or proven cervical spine injury who is displaying signs of airway compromise. To achieve this positioning, place one hand on the patient’s forehead, directing force posteriorly. With your other hand, use your index a middle fingers to bring the chin anteriorly. These actions will do much to eliminate any airway obstruction and will place the patient in the ideal “sniffing position” for potential intubation.

2. Jaw Thrust
This strategy can be used in the patient with suspected or proven cervical spine injury. Using your middle and index fingers on either hand, put pressure on the angle of the mandible bilaterally. This will bring the patient’s tongue into a more anterior position, diminishing upper airway obstruction.

[3] What is a laryngeal mask airway (LMA) and when is it used? How are they sized?

What are they?

● Laryngeal mask airways (LMA’s) are a type of extraglottic airway device that are readily used in both the in hospital and prehospital setting. These devices are typically ovoid in shape and are designed to be inserted blindly into the oropharynx of an anesthetized patient. They form a seal above the glottis and allow for ventilation through a centralized channel.

When are they used?

● LMA’s are typically used in elective anesthesia cases that are of short duration. However, given their ease of use, they can be used as a backup airway in the case of a failed intubation and can be used as a temporizing measure that could be used in place of traditional bag valve mask ventilation to bridge someone to definitive airway control. LMA’s can also be used in the prehospital setting to better control the airways of EMS patients.

How are they sized?

● LMA’s are sized by the body weight of the patient. When in doubt, you can usually find weight ranges printed on the LMA!

[4] Does presence of a gag reflex correlate with ability to protect an airway?

Answer: No.

It is important to note that the gag reflex is actually absent normally in approximately 25% of adults. The fact that it is not present does not indicate that an individual is unable to protect their airway. To truly assess an individual’s capacity to protect their airway, consider the following factors:

    • The patient’s ability to voluntarily swallow
    • The patient’s ability to handle secretions
    • The patient’s level of consciousness
    • The patient’s ability to phonate in response to voice commands

[5] How do you examine for airway obstruction?

Signs of airway obstruction (The S’s). See this great Canadiem article here.

  • Silent Chest, See-Saw Chest
  • Secretions
  • Snoring (tongue relaxation)
  • Smash (teeth/blood in airway)
  • Stridor
  • Singe/sputum (carbonaceous) – risk of airway burns
  • Stab/swelling (impending obstruction by hematoma)
  • Sleepy – low GCS (unable to protect the airway)
  • Angioedema/Ludwig’s angina
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Owen Scheirer

Owen Scheirer

Owen is a resident in the FRCPC Emergency Medicine program at the University of Saskatchewan. When he's not running around the emergency department, he's outside cycling, or hanging out with his wife and dog.
Dillan Radomske

Dillan Radomske

Dillan Radomske is an Emergency Medicine resident at the University of Saskatchewan. He is passionate about technology-enhanced medical education, podcast creation and production, and Indigenous advocacy. He is one of the new CRACKCast hosts, and aspires to continue to contribute to the field of FOAMed in the future.
Dillan Radomske
- 2 months ago