Difficult Airway Flashcards
1
Q
Definition of the difficult airway?
A
- Difficulty with ventilation by mask or supraglottic airway (SGA)
- Difficulty with endotracheal intubation
- Or both
- ASA definition:
- ** > 3 attempts w/ DVL (average laryngoscope) for endotracheal intubation
-
** > 10 minutes for endotracheal intubation
- major factor in anesthesia morbidity
2
Q
What is a difficult mask or SGA?
A
- Inability of an unassisted anesthesia clinician to maintain alveolar oxygen delivery or reverse signs of inadequate ventilation
- D/t inadequate mask seal, excessive gas leak, or excessive resistance to ingress/egress of gas
- Visualize by:
- Inadequate chest rise and fall, absent breath sounds, cyanosis, inadequate oxygen saturations, inadequate spirometric measurements of exhaled gases, or signs of hypoxemia or hypercarbia
3
Q
Most common predictors of difficult airway in closed claims analysis?
A
- airway obstruction
- past h/o difficult intubation
- Mallampati 3-4
- limited cervical spine extension
4
Q
Airway review of nares?
A
- Primary function is warming and humidification of air
- Olfaction/speech
- Roof → formed by the cribriform plate of the ethmoid bone
- Fragile structure
- Mucosal lining → very vascular (susceptible to trauma)
- apply vasoconstrictors to help prevent epistaxis
5
Q
Airway review of pharynx?
A
- muscular tube that extends from the base of the skull down to the level of the cricoid cartilage (inferior boarder- C6 vertebral level) and connects the nasal and oral cavities to the larynx and esophagus.
- Respiratory & digestive fx
- Becomes continuous w/ esophagus
- In an awake patient, the pharyngeal musculature helps maintain airway patency.
- Sedation → Loss of pharyngeal muscle tone
- Primary cause of airway obstruction
- Sedation → Loss of pharyngeal muscle tone
- Divided into:
- Nasopharynx
- oropharynx
- Hypopharynx (laryngopharynx)
7
Q
Airway review of larynx?
function?
location?
composition?
A
- Fx:
- Phonation- contains VC
- airway protection- prevent food aspiration into trachea while breathing
- Located between C3 – C6
- Complex structure of cartilage, muscle, and ligaments that serves as the inlet to the trachea
- Superior portion:
- Epiglottis- attached to hyoid bone (attached to inferior pharynx)
- Inferior portion: attached to superior trachea
- Superior portion:
- 9 cartilages
-
3 Unpaired –
- Epiglottis
- Thyroid- “thyroid ring” (only cart to encircle trachea completely)
- Cricoid
- 3 Paired – arytenoid, corniculate & cuneiform
-
3 Unpaired –
- Cricoid is only complete cartilaginous ring
8
Q
What provides sensory to the airway?
A
-
Trigeminal (CN 5)
-
Ophthalmic (V1): anterior ethmoid
- Anterior mucous membranes
-
Maxillary (V2): sphenopalatine
- Posterior mucous membranes
-
Mandibular (V3): lingual
- Anterior 2/3rds of the tongue
-
Ophthalmic (V1): anterior ethmoid
-
Glossopharyngeal (CN 9)
- Roof of pharynx, tonsils, and under surface of palate
- Posterior 1/3rd of tongue
-
Vagus (CN 10)
- Superior laryngeal nerve (has internal (sensory) and external (motor) branch )
- Below epiglottis–> VC
- Internal branch of superior laryngeal: laryngeal mucosa
- Recurrent laryngeal nerve
- Below vocal cords
- Superior laryngeal nerve (has internal (sensory) and external (motor) branch )
9
Q
Airway review of trachea?
specifications and measurements?
A
- Specifications:
- tubular structure
- Starts C6 → extends to T5 (carina/bifurcates)
- Anterior aspect:16-20 C-shaped cartilages (horseshoe)
- Posterior aspect: Membranous/flat– (good landmark for fiberoptic intubations)
- Measurement:
- Length: ~10-16 cm long (avg.)
- Diameter: tracheal lumen narrows slightly as progresses towards carina
- M: 22 cm
- W: 19 cm
- Distance from tracheal carina to the bifurcation of the left upper and left lower lobe is approximately:
- M: 5.0 cm
- W: 4.5 cm
11
Q
What provides motor innervation to the airway?
A
Trigeminal (CN 5): mandibular branch (V3)
- Muscles of mastication
Hypoglossal (CN 12)
- All intrinsic and extrinsic muscles of tongue
- except palatoglossus muscle (vagus)
Vagus (CN 10)
-
Recurrent laryngeal nerve
- All intrinsic muscles of the larynx
- except the cricothyroid muscles
-
Posterior cricoarytenoid muscle
-
sole muscle responsible for abduction of VCs
-
Unilateral RLN injury: hoarseness
- concern in ACDF and thyroid sx
- Bilateral RLN injury: partial vs. complete airway obstruction → extreme AW emergency!
-
Unilateral RLN injury: hoarseness
-
sole muscle responsible for abduction of VCs
- All intrinsic muscles of the larynx
-
Superior laryngeal nerve (internal and external branch)
- External branch: cricothyroid muscle (motor)
- tenses and adducts VCs
- Injury: voice quality, generally not dangerous
- tenses and adducts VCs
- External branch: cricothyroid muscle (motor)
12
Q
Components of airway assessment?
A
- History – anesthesia, medical, surgical
- Previous AW issues in the past?
- Head/Neck sx in past?
- Dental damage?
- prolonged airway swelling?
- Physical exam
- Thorough airway exam
- Questions r/t the airway
- Documentation
- Better to falsely predict a difficult airway and be prepared
- ***No infallible method to identify a difficult airway
13
Q
Appropraite assessment of previous intubation history?
A
- *One of the most predictive factors for difficult intubation is a history of previous difficult airway or intubation.
-
Inquire about previous anesthetics
- Dental damage?
- Prolonged/ severe sore throat?
- Were you advised on intubation techniques for the future?
- Are anesthesia records available? → LOOK
- Documents/registry?
-
Inquire about previous anesthetics
- On the other hand, a history of easy intubations do not rule out the possibility of difficult ventilation or intubation.
14
Q
What are congenital syndromes associated with difficult airway?
A
-
Pierre-Robin Syndrome (congenital compression/genetic)
- Micrognathia, macroglossia, cleft soft palate
-
Treacher-Collins Syndrome (genetic – Tcof1)
- Auricular and ocular defects, malar and mandibular hypoplasia
-
Goldenhar’s Syndrome (Unknown/Branchial arch development)
- Auricular and ocular defects, malar and mandibular hypoplasia
-
Down’s Syndrome (trisomy 21)
- Poorly developed or absent bridge of the nose - macroglossia
-
Klippel-Feil Syndrome (GDF3, GDF6, MEOX1)
- Congenital fusion of a variable number of cervical vertebrae – limited ROM
-
Turner Syndrome
- Frequent/ complex abnormality affecting women
- Short neck, maxillary & mandibular hypoplasia
15
Q
Medical history concerns with airway assessment?
A
- Airway pathology (tumor)
- Mediastinal mass- CT/Xray useful
- Thyroid dx → diff breathing lying flat/swallowing
- Trauma- C/S
- Arthritis/ ankylosing spondylitis
- Obesity
- OSA
- Pregnancy
- Acromegaly
- Burns
- Genetic disorders
- Musculoskeletal deformities
- Radiation therapy
16
Q
What are infections that can lead to difficult airway?
A
- Epiglottitis
- Potentially life-threatening bacterial infection
- May lead to emergent airway management
- Croup
- Viral mediated inflammation
- Steeples sign- subglottic tracheal narrowing noted on CXR
- Laryngeal edema/airway irritability
- Retropharyngeal abscess
- Distortion of airway/ mask ventilation and intubation difficult
- Ludwig’s angina
- Abscess in floor of the mouth under the tongue
- Edema/obstruction/distortion of airway/trismus →
- Video laryngoscopy/fiberoptic intubation optimal!
- Abscess in floor of the mouth under the tongue
17
Q
Other conditions that can lead to difficult airway?
A
- Head/Neck Radiation
- Friable tissue, edema, limited ROM/mouth opening
- Morbid Obesity
- Short thick neck, redundant tissue, large tongues and apnea likely
- Acromegaly
- Macroglossia and hypertrophy of laryngeal/pharyngeal tissue
- Burns
- Edema, distortion, fixation of tissue from scars, bronchospasms
18
Q
What previous surgical history predispose to difficult airways?
Surgeries that can cause postop airway issues?
A
- Previous Surgical History
- Tracheostomy or scar
- Have you been intubated since tracheostomy taken out?
- May need smaller ETT
- Neck dissection
- UPPP
- Cervical neck fusion → video/fiberoptic tech optimal
- Tracheostomy or scar
- Post-op Period Emergencies (hematoma)
- Thyroidectomy
- Tonsillectomy
- Neck Dissection (Hematomas postop period)
19
Q
Physical characteristics to look out for on preop assessment of airway?
A
- Facial deformities?
- Neck-size circumference + length
- Goiter?
- Mandible-receding?
- Facial hair?
- Cervical collar?
- Trachea midline?
- Nares-size? Open? Mouth breathing? Flaring?
- Mouth-lips, tongue, tissues-color, size, condition?
20
Q
Features of an airway exam?
A
- Mouth opening
- Size & mobility tongue
- Palate- high or arched?
- Visualization of supraglottic masses/ tonsillar hyperplasia?
- Size & shape mandible; maxillary overgrowth?
- TMJ –degree of motion? Dislocations?
- Ability to advance lower incisors in front of upper?
- Neck circumference
- Thyromental distance
- Mallampati
- Dentition
- **Evaluating for the ease of DL, but predicting difficult DL remains, in large part and enigma
21
Q
How do we assess mouth opening?
A
- Inter-incisor distance/gap:
- Measured from upper to lower incisors
- Normal: > 4.5 cm
-
Abn: < 3 cm (2 finger breaths) (some video need 2 cm for insertion)
- suggestive for difficult airway
- Measured from upper to lower incisors
22
Q
What is the modified mallampati classification system?
A
- assess relationship b/t tongue size and oropharyngeal cavity
-
Diff mask/vent & diff laryngoscopy:
- III: visualize base of uvula only
- IV: soft palate no visible
-
Diff mask/vent & diff laryngoscopy:
Tests → POOR predictor ALONE (use together)
23
Q
What is thyromental distance? Sternomental distance? Purpose?
A
Helps determine how readily the laryngeal and pharyngeal axis aligns
-
Thyromental: Measure from upper edge of thyroid cartilage to chin/jaw with the head fully extended
- A short thyromental distance = an anterior larynx
-
Normal: 6.5 cm
- > 7 cm = usually easy intubation
- Diff Intubation: < 6 cm
-
Normal: 6.5 cm
- A short thyromental distance = an anterior larynx
-
Sternomental: Upper border of manubrium (sternal notch) to the tip of the mandible w/ head extended
- Sternomental distance:
Diff Intubation = < 12.5 cm
25
Q
What is the cormack and lehane classification system?
A
- A. Class I: full view of the glottis
- *** Likelihood of difficult intubation Class I: < 1%
- B. Class IIa: partial view of the glottis
- *** Likelihood of difficult intubation Class IIa: 4.3-13.4%
- B. Class IIb: only the posterior glottis is seen or arytenoid cartilages
- *** Likelihood of difficult intubation Class IIb: 65-67.4%
- D. Class III: only epiglottis is seen
- *** Likelihood of difficult intubation Class III: 80-87.5%
- E. Class IV: Neither glottis nor epiglottis is seen
- *** Likelihood of difficult intubation Class IV: very likely
27
Q
What neck circumference is predictive of a difficult airway?
A
-
Predictive diff visualization of glottic opening: 17 in (42 cm)
- Increase in pretracheal and soft tissue ass w/ DAW
- Inability to achieve optimal neck extension
- Fatty tissue around posterior pharyngal/buccal skin folds → diff visualizing of glottic opening
29
Q
What are some difficult airway techniques and equipment?
A
- Equipment/techniques to manage difficult airway include, but are not limited to:
- Awake intubation
- Video-assisted laryngoscopy
- Intubating stylets or tube-changers
- SGA for ventilation
- SGA for intubation
- Rigid laryngoscopes
- Fiberoptic guided intubation
- Lighted stylets or light wands
- Cricothyrotomy
34
Q
What are the regional methods to block the glossopharyngeal nerve?
A
Regional- 2 approaches
-
Oral approach (for Glossopharyngeal nerve block)
- 25g needle inferior to tonsil pillars (base of tongue)
- after mouth numbed with lidocaine, can retract tongue medially better to access pillars
- 1-2 mls 2% lidocaine (gargle)
- Need sufficient mouth opening to access the pillars
- point of injection at caudal aspect of posterior tonsillar pillar. ~0.5 cm lateral to edge of tongue where it joins edge of mouth
- 25g needle inferior to tonsil pillars (base of tongue)
-
Peristyloid approach
- Posterior to styloid process
- glossopharyngeal N runs nearby
- can palpate styloid process but requires deep palpation
- pt in supine with head neutral. styloid process midpoint at angel to jaw to tip of mastoid process
- place needle perpendicular aiming to hit styloid process. once contact made, walk needle posteriorly until contact lost
- Close proximity to **internal carotid
- 5-7 mls of 2% lidocaine (after negative aspiration)
- Posterior to styloid process
35
Q
What are the approaches to block the superior laryngeal nerve?
A
- Superior Laryngeal Nerve Block (2 approaches)- innervation to laryngeal structure above VC
- Splits → internal/external branch
- Internal branch→ penetrates thyrohyoid membrane 2 cm over greater cornu
- External branch → descends on larynyx to sternohyoid muscle
- Splits → internal/external branch
-
External approach
- Supine with neck extended (need ability to extend neck)
- Identify the greater hyoid bone
- Underneath angle of mandible
- Displace hyoid toward clinician
- Insert 23/25 g – 1.75 cm over inferior border of cornu and walk of bone inferiorly- inject 2 cc 2% lido. If you don’t pierce the thyrohyoid membrane, then external and internal SLN blocked
- Pass through thyrohyoid membrane- if you pierce the thyrohyoid membrane, will only block internal branch.
- Aspirate
- Inject 1-2 mls of local (blocks internal/external branches of SLN)
- Need to complete bilaterally….
- If too far and penetrate thyrohyoid membrane → only will block internal branch (NO!)
-
Oral/internal:
- Lidocaine soaked gauze in piriform fossae
- 5-10 mins
53
Q
Techqniue for needle cricothyrotomy?
A
- Needle cricothyroidotomy should be performed with universal precautions and sterile technique. The puncture site is cleansed with povidone-iodine solution after sterile gloves have been donned.
- Hold the trachea in place and provide skin tension with the thumb and middle finger of the non-dominant hand placed on either side of the trachea. Use the index finger to palpate the cricothyroid membrane.
- Hold a 3 to 10 mL syringe half-filled with saline attached to the over-the-needle IV catheter in the dominant hand.
- Place the catheter in the midline of the neck at the inferior margin of the cricothyroid membrane (to avoid the cricothyroid blood vessels located superiorly and laterally). Direct it caudally (toward the feet) at an angle of 30 to 45 degrees.
- Puncture the skin and subcutaneous tissue. Advance the catheter while continuously applying negative pressure on the syringe, until air bubbles are seen, confirming intratracheal placement.
- Advance the catheter forward off the needle until its hub rests at the skin surface. Remove the syringe and the needle.
- Reattach the syringe to the catheter and again aspirate for air to confirm that the catheter remains in the trachea.
- Hold the catheter firmly in place at all times or delegate an assistant to do this to reduce the chance of kinking or dislodgement, even after it has been secured with suture material.
- Needle Cricothyroidotomy
61
Q
Steps involved for extubation from low-risk algorithm?
A
- 100% O2
- Remove sx
- Insert bite block
- Sitting position
- Reverse NMB
- SV- normal RR
- Minimize head and neck movement
- Provide PPV
- Deflate cuff
- Remove ETT
- Continue O2 supplement
62
Q
At risk algorithm for extubation?
What are some exclusions for extubation?
A
- Risk factors present
- Preexisting difficulty:
- Ex: Obesity/OSA, pts w/ risk for aspiration
- Perioperative AW deterioration:
- AW normal @ induction → then become diff
- Ex: distorted anatomy, hemorrhage, hematoma, edema from sx/trauma/nonsx factors
- AW normal @ induction → then become diff
- Restricted AW access
- Ex: shared AW, ROM limited
- Preexisting difficulty:
- Exclusion of extubation:
- Impaired resp fx
- CV instability
- Neurologic/neuromuscular impairment
- Hypo/hyperthermia
- Clotting abnormalities
- Acid/base or electrolyte imbalances
64
Q
How do you use an airway exchange catheter (AEC)?
A
- Depth of AEC. Distal tip must remain above carina (never beyond 25 cm)
- Insert lubricated AEC through ETT
- Employ pharyngeal suction
- Remove ETT over AEC. Monitor depth
- Secure AEC to cheek or forehead
- Record depth at teeth/lips/nare (label)
- Check that there is a leak
- Supplemental oxygen applied
- If not tolerated, check depth, inject lidocaine
- Remain NPO
- Must go to ICU
- Can be tolerated up to 72 hrs (before being removed)
