Case 43 - The Difficult Airway Flashcards
1
Q
What are predictors of difficult mask ventilation?
A
Predictors of Difficult Facemask Ventilation
- previous airway records indicating so
- obesity
- beard
- edentulousness
- history of snoring
- history of OSA
- facial abnormalities (dressings, burns)
- massive jaw
- age > 55 yo
- large tongue
- poor atlanto-occipital extension
- pharyngeal pathology (tonsil hypertrophy, laryngeal tonsil abscess)
2
Q
What is the sniffing position?
A
- Airway contains three visual axes:
- long axes of mouth
- oropharynx
- larynx
Sniffing position
- attempt to align these three axes together
- Cervical flexion - brings pharyngeal and laryngeal axes together
- atlanto-occipital extension - brings oral axis in line with other two axes
**inability to assume sniffing position is a predictor of difficult intubation**
3
Q
what are example of problems that prevent the sniffing position?
A
- pain, tingling, numbness with sniffing position
- c-spine arthritis
- cervical ankylosing spondylitis
- unstable c-spine fractures
- cervical collars
- morbid obese patients with posterior neck fat pads
unable to assume sniffing position –> predictor of difficult intubation
4
Q
Why is Mouth opening important during airway examination?
A
- allows examiner to determine available space for placing and manipulating laryngoscope and tracheal tube
- allows examiner to see soft palate, hard palate, tonsils, and uvula –> MP classificaiton –> predictor of difficult intubation
measurements
- intercisior distance >3 cm or 2 fingerbredth
- MP class
- dentition
- TMJ dysfunction
5
Q
How does dentition affect airway manipulation?
A
- instrumentation of airway places teeth at risk for damage
- poor dentition/loose teeth can be accidentaly knocked out, enter trachea, migrate to lung, predispose to abscesses
- poor dentition/loose teeth forces one to avoid placing pressure on these teeth, which may make one manipulate the laryngoscope into a less than ideal position with poor view of glottis.
- prominent maxillary incisiors –> forces one to achieve a different line of sight, providing a less than ideal view of the glottis.
6
Q
How is evaluating the tongue a predicitor of difficult intubation?
A
- during induction, tongue falls posteriorily obstructing the line of sight into glottis.
- laryngocopes are designed to push the tongue anteriorly –> move it from a posterior obstructing position to a new anterior non-obstructing positiong between the mandibular spaces
-
goal - assess tongue size in relation to size of mouth, oropharynx, and mandible.
- large tongue compared to size of mouth interferes with visualization
Predictor of difficult intubation
- Macroglossia - harder to displace tongue anteriorly, will still take up real estate during laryngoscopy -> obstruct line of sight
- Micrognathia - normal tongue fits poorly into small mandibular space, unable to displace all of tongue anteriorly –> obstruct line of sight
7
Q
What is the Mallampati-Samsoon classificaiton system?
A
- initially developed to relate the size of the tongue to the oropharygneal structures identified.
- as tongue size increase, fewer structures are visualized, and laryngoscopy becomes more difficult.
MP 1
- see tonsillar pillar and fauces, uvula, soft palate
MP2
- partial tonsilar pillar and fauces, uvula, soft palate
MP 3
- soft palate, base of uvula
MP 4
- hard palate only
8
Q
What is the upper lip bite test?
A
TMJ
- laryngoscopy –> not only displaces tongue anteriorly, but lifts mandible anteriorly as well.
- TMJ
- hingelike motion for mouth opening
- gliding (translational) movement –> allows mandible to slide anteirorly across maxilla.
- inability for translational movement makes intubation difficult
Upper lip bite test
- assess for TMJ displacement (gliding movement)
- protrude lower teeth as high on upper lip as possible (beyond vermilion border = upper lip)
9
Q
What is the purpose of measuring the thyroidmental distance?
A
- TM distance is a good estimate of the size of the mandible.
- small mandibular size results in less mandibular space to displace the tongue anteriorly into –> makes intubating difficult.
- use thyroid notch (Adam’s Apple) and measure to mentum (chin).
- >6 cm or 3 finger-bredths –> easy intubation
- <6 cm or 3 finger-bredths –> sign of difficult intubation
10
Q
What are predictors of Difficult Intubation?
A
- History
- long upper incisiors
- interincisor distance < 2 fingerbredth (or <3 cm)
- overbite (max incisors override mandib incisors)
- poor upper lip bite (inability for mandib incisors to protrude above upper lip = poor TMJ gliding mvmt)
- poor cervical range of motion
- TM Distance < 3 fingerbredth (or < 6 cm)
- MP III or IV
- Neck - short, thick
- palate shape - high arched or narrow
11
Q
What is the cormack and lehane grading system?
A
- grading system for comparing laryngoscopic view
Grades 1 to 4
- grade 1 = entire glottic opening
- grade 2 = posterior laryngeral apateure, unable to see anterior portion
- grade 3 = soft palate and epiglottis, no part of larynx
- grade 4 = soft palate, no part of epiglottis
12
Q
are the risk factors for difficult intubation reliable predictors of difficult intubation?
A
No!
- no single factor reliably predicts difficult intubation
- likelhood of dificult intubation increaes when multiple predictors are present in a patient at the same time.
-
Study by Rock:
- MP 3-4 + short neck + receding mandible + protruding maxillary incisors –> approx 90% probability of difficult intubation
13
Q
How is an anticipated difficult intubation approached?
A
- Awake vs asleep intubation
- Spontaneous vs supported breathing
- oral vs nasal ett
Awake FOB
- Give anticholinergic 20-30 min prior to procedure
-
antisialagogue effect
- reduce secretions –> obstruct view
- desiccate mucosa –> allows better contact between local anesthetic topicalization and mucosa –> provides better airway anesthesia
-
antisialagogue effect
- Topicalize with lidocaine 4%
- glossopharyngeal nerve at tonsillar pilllars
- superior laryngeal nerve (internal branch) at pyriform fossae located on either side of base of tongue
- recurrent laryngeal nerve - walls of trachea
- Palatine nerves (V2 maxillary branch of trigmenal) -> block for nasal route
- if nasal intubation, use Afrin (oxymetazoline) = vasoconstrictor
14
Q
You induce a patient, after induction you cannot intubate, but can mask ventilate, what do you do?
A
- why is it difficult?
- secretions
- floppy epiglottis (miller may be better)
- position not adequate
- anterior larynx
- difficult threading tube due to getting caught on arytenoid
- Grade III, IV view
Options for Failed traidtional tracheal intubation under general anesthesia (non-emergency pathway)
- continue anesthesia by facemask
- continue anesthesia with supraglotic device
- awake patient
- consider regional anesthesia
- awake FOB
- reattempt intubation with change in position (sniffing position optimized), glidescope, different blade/handle, fiberoptic intubation, aintree catheter intubation, intubating LMA, glidescope assisted FOB intubation, intubating stylet (gum elastic bougie)
initial tracheostomy indicated for laryngeal fractures or abscesses that impinge on the airway
15
Q
After induction, ventilation and intubation is impossible. What do you do?
A
- Call For HELP!
- notify surgeon/ENT Team for possible surgical airway required
- Place supraglottic airway –> LMA, laryngeal tube, combitube
- Able to ventilate with SGA –> go to non-emergency pathway
-
unable to ventilate through SGA –> Emergent pathway
- Surgical Airway - surgical cricoidthyroidotomy (incision of cricoidthyroid membrane with placement of trach or ett via seldinger technique), needle cricoidthyrodiotomy with jet ventilation, retrograde intubation
