Airway Flashcards
Assess difficult BMV by?
Mallampati score
Radiation to neck
Beard
Old >55yrs
Obese
No teeth, thyromental distance <6cm
Snorning, sleep apnoea
Anterior column components of airway assessment
Mouth opening - Mallampati
Teeth - prominent front teeth
Shortening of TMD
Size of tongue
Jaw protrusion
Middle column assessment of airway
History of stridor or hoarse voice
Nasopharyngoscopy
CT / MRI
Mainly looking for abnormality of airway passage - foreign body, tumours
Posterior column assessment
Range of neck movement
- Flexion of lower C spine
- Extension of the occipito-atlanto-axial complex
Neck circumference of > 43cm = difficult
Mnemonic for difficult LMA? RODS
Restricted mouth opening
Obesity, OSA
Distorted airway
Stiff lungs
Difficult intubation predictors
Long upper incisors
Poor jaw protrusion
Small mouth opening
Limited movement of neck
Short TMD
High MP score
What are the 3 cardinal signs of upper airway obstruction
Stridor
Difficulty swallowing
Muffled voice
What did the landmark trial for THRIVE show?
Patel’s study
- Average apnoea time of 17 mins
- Small rise in EtCO2 of 1.1mmHg per min
What are the risks and contraindications of high flow?
Contraindicated in CSF leak, oesophageal perf, BoS fracture, pneumothorax
Risks: barotrauma, gastric distention
How is preoxygenation achieved?
EtO2 >0.9
Adequate seal
3mins of TV ventilation or 8 deep breaths in 60s
Benefits of HFNP oxygen
reduces dead space, generates PEEP, and reduces work of breathing
What does TRHIVE stand for?
Transnasal humidified rapid insufflation ventilatory exchange
How much does EtCO2 rise per min in apnoea
1.8mmHg per min
What’s the pressure relief valve set at for Laerdal bag?
60cmH2o for adult
40 for children
What are the goals of assessing an obstructing airway
Nature, location and extent of the lesion causing obstruction
Urgency of airway management
What are the four choices of airway management in an obstructing airway?
Awake surgical tracheostomy
Awake intubation
Asleep SV intubation
Asleep intubation with paralysis
Measures to manage obstructing airway?
Sit upright
Apply O2 via HFNP to reduce WoB
Nebulised adrenaline 1-4mg
IV steroids
Helium O2 mixture
Why is inhalational induction no longer recommended for an obstructing airway?
In theory it maintains SV, can reverse volatile anaesthesia in failure
However, complete airway obstruction can occur, resulting in hypoxia and inability to decrease anaesthetic depth
Options of airway management for advanced laryngeal tumour
- Inhalational induction with double set up
- If obstruction moderate, and intubation deemed possible on FNE.
- 2 attempts at intubation. If failed, then surgeon to perform tracheostomy - Tracheostomy under LA in severe pathology
Why is AFOI not used in laryngeal tumour?
Risk of topicalisation causing laryngeal spasm
Sedation causing complete obstruction
Airway diameter too narrow - cork in bottle
Risk of bleeding
Technical difficulty can lead to loss of airway
What are the newer techniques for managing advanced laryngeal tumours?
AFOI, in skilled operator, coaching pt through cork in bottle stage
Awake videolaryngoscopy with fiberoptic intubation - displacing the tongue for greater glottic access
SV TIVA with HFNP
What is Ludwig angina?
Bilateral bacterial cellulitis of the entire floor of mouth, usually an extension of a dental infection
How does Ludwig’s angina change the airway?
Elevation and posterior displacement of the tongue
progressive swelling of epiglottis and oropharyngeal tissue
Can cause truisms - reflex spasm of the master and medial pterygoid muscles
What symptoms will make AFOI difficult in patients post neck radiotherapy?
Usually not difficult.
However, if preop hoarseness and stridor, known to have laryngeal oedema = difficult
Progression of symptoms in post thyroid neck haematoma?
Subtle voice change or hoarseness
Dyspnoea and stridor are late signs
What’s the cause of airway obstruction in post thyroidectomy haematoma?
Spread of blood in the tissue plane - direct compression of airway
Compression of veins and lymphatics -> airway oedema
Why and when should you reopen the neck in post thyroid haematoma?
If patient is distressed and airway threatened.
Unwise to attempt intubation in a symptomatic patient without opening haematoma
Allows access to rapid tracheostomy
Airway plan for post thyroidectomy haematoma?
Open neck wound
AFOI preferred - very likely to succeed.
Inhalational induction
IV induction + paralysis if surgeon ready to perform tracheostomy when intubation fails.
Double set up to perform surgical airway
Symptoms and signs of acute epiglottis?
sore throat, odynophagia (pain on swallowing)
fever, muffled voice, pharyngitis signs
Respiratory distress
Why is inhalational induction the traditional approach for epiglottis?
LA could precipitate loss of airway
What are some key points when managing the airway of pt with acute epiglottis
Avoid LA for intubation
Double set up - plan B surgical airway should intubation be impossible
- Tracheostomy performed with volatile anaesthetic + SV
Avoid muscle relaxant traditionally
Use a smaller than usual ETT
What’s the pathophysiology of hereditary angioemdema?
How is it treated?
C1 esterase inhibitor deficiency.
Treat with FFP, containing C1 esterase inhibitor
Why can’t SAD be used in C spine injury?
High pressure against C spine may cause posterior displacement if spine is unstable
What are the C-spine abnormalities possible in rheumatoid arthritis
Subaxial subluxation
Atlanto-axial subluxation
What’s the radiological finding of atlanto-axial subluxation
Widening of the distance between arch of C1 and the dens of >3mm in adults in fully flexed position.
Cyanide poising
- lab indicator?
- antidote?
unexplained lactic acidosis >10mmol/L
Hydroxycobalamin 5g IV over at least 15 mins
Sodium thiosulphates - slower effect, give in combination with hydroxycobalamin
In laryngeal trauma (tracheal transection) - what is the preferred airway management technique and why?
Fibreoptic intubation under LA
- Careful passage through the injured area.
- BMV, or ETT passing partially transected trachea can create false passage -> complete airway obstruction
In emergency, can use direct placement of a smaller ETT, with position checked with fiberoptic scope.
Surgical tracheostomy is the favoured approach
Threatened obstructed airway in an uncooperative patient - options?
Safest = volatile induction, despite risk of gastric regurgitation. Maintain SV
Double set up, as can perform tracheostomy should intubation fail
Airway considerations for high grade maxillary fractures?
Le Fort 3 - midface is mobile, can displace posteriorly to obstruct airway
- Patient will position self to maintain airway - take note of position
- Can lift bone manually
Bleeding can be severe.
Beware of BoS fracture - no high flow / THRIVE, or C-spine # -> need for MILS.
Head injury with reduced conscious state = impaired ability to protect airway
Describe TIVA SV induction
Marsh model
Cpt 2-3 mcg/ml starting
Increase Cpt by 0.5-1 when the Ce reaches a point below Cp
Continue until Ce of 5-6mcg/ml -> laryngoscopy.
Spray cophenylcaine onto epiglottis, vocal cords, trachea.
Suspension laryngoscopy when Ce 6-7 mcg/ml
Absolute contraindications to AFOI
Patient refusal
Allergy to LA
Relative contraindications to AFOI
Blood and secretion in airway - difficult visualisation
Gross airway distortion, fixed laryngeal obstruction - Cork in bottle effect
Significant respiratory distress or airway compromise - LA may precipitate spasm
Disadvantages of nasal AFOI
epistaxis
smaller tube use
patient’s discomfort
topicalisation includes nasopharynx
Disadvantages of oral AFOI
natural conduit of the passage of the tube is lost - needs more advanced fibreoptic skills
Patient bite on scope
Can gag as scope might touch the oropharynx
Holdup of tube at the cord
Reduced MO = difficult
What’s the main purpose of Berman airway?
Protect the fiberoptic scope and facilitate direct passage to larynx
What’s the advantage of Ovassapian airway over the Berman?
Smaller size, better tolerated, easier to remove post intubation
Max dose of lignocaine from current recommendations?
Reasonable to use 7-9mg/kg
DAS suggests not exceeding 9mg/kg
What does each co-phenylcaine spray contain?
5mg lignocaine, 0.5mg phenylephrine
What are the target nerves when topicalising for AFOI?
Trigeminal nerve - sensory to nasal cavity, anterior 2/3 of tongue
Glossopharyngeal nerve - posterior 1/3 of tongue, soft palate, palatoglossal folds, lingual surface epiglottis
Vagus - internal branch of superior laryngeal nerve for larynx above cord, RLN for sensory below cords
Aims of topicalisation in AFOI?
Ablate gag reflex - success when no response when touching pharynx
anaesthetise vocal cords and trachea
anaesthetise nose
How does a DeVilbiss atomisation device work?
Generates very small LA droplets for efficiency passage through airway and absorption via mucosa
What’s the endpoint for airway topicalisation?
Ablation of gag reflex
Change in voice
What is LASER?
light amplification of stimulated emission of radiation.
Advantages of laser surgery?
Precise cutting
Low tissue reaction
Simultaneously cut and cauterise - reduce bleeding
Disadvantages of laser surgery
Airway fire
Iatrogenic burns of surrounding tissue
Scarring
ETT cuff rupture
Staff protection measures from laser?
Warning signs or locks on OR doors
Protective glass
Skilled operator
Regular training / inservice
Protection from fire - bottle of water set to douse the fire
Hazards of laser
eye damage, skin burns, airway burns
Atmospheric contamination with laser plume - can cause laryngospasm / viral transmission
Tissue perforation
What are the three approaches to micro laryngeal surgery?
- Conventional low pressure ventilation with either microlaryngeal tube or laser-flex tube
- Subglottic jet ventilation
- no-tube technique
What is the crucial distinction between patients with laryngectomy vs. tracheostomy?
Tracheostomy patients have a potentially patent upper airway.
What is the function of an obturator in tracheostomy tube?
Fits within the trache tube, acts as an introducer, with a smooth, rounded tip to assist passage of tube.
What is the function of an inner cannula for tracheostomy?
Allows cleaning of build up of secretions
Blocks the fenestrated holes of the outer tube
Steps of emergency management for tracheostomy
Apply O2 upper + trache site.
Assess patency by passing suction tube down. Can’t pass -> let down cuff
If can’t do either, remove tracheostomy
If can’t breath, positive pressure ventilate via either ends
No improvement - intubate via stoma or orally
after how many days would you expect a well established stoma for tracheotomy?
7-10 days
