Anaesthesiology - Airway management Flashcards
Modalities of airway management
Indications of airway management
Indications for airway management:
□ Need for airway protection, eg. upper airway obstruction, risk of aspiration, ↓consciousness
□ Need for ventilation, eg. anaesthesia with NMB, IPPV indicated (for eg. resp failure)
□ Need for oxygenation, eg. significant unrelieved respiratory distress, blood gas abnormalities
Outline PE for airway exam
Features of difficult airway
General exam:
- Anxious, sitting upright or in tripod position
- Diaphoresis
- Cyanosis
- Altered mental status
- Obesity
- Obvious head and neck pathology (e.g. massive goiter)
- Medical equipment (e.g. halo traction, neck collar)
Oro-facial exam:
- Loose teeth/ no teeth, Dentures, SIngle incisors, overbite/ buck teeth
- Beard
Respiratory exam:
- Respiratory distress: Tachypnea, SoB, Use of accessory muscles and in-sucking of ICS
- Hoarseness/ voice change
- Snoring, Stridor, Wheezes, Crackles
- Mediastinal deviation with increased resonance (tension pneumothroax)
- No chest expansion with inspiration
- Silent chest
- No perceivable airflow
List predictive tests for difficult laryngoscopy
- Mallampati Score
- Interincisor Distance
- Thyromental distance
- Cervical spine movement
- Sternomental distance
- Jaw protrusion
Combined test: Mallampati and Thyromental distance are more predictive than individual tests
Outline Mallampati Score for ease of laryngoscopy
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Mallampati score: pillars visible (I), fauces visible (II), base of uvula visible (III), only hard palate visible (IV)
Outline Thyromental distance for ease of laryngoscopy
- Distance >6.5cm is rarely associated with difficulty
- Distance 6-6.5cm may be associated with difficult
laryngoscopy but intubation is usually possible - Distance < 6 associated with difficult direct laryngoscopes
Define the interincisor gap and sternomental distance for ease of laryngoscopy
Interincisor gap
* The distance between the incisors with mouth fully open
* It is affected by TMJ and upper C spine mobility
* <3cm = intubation more difficult
* <2.5cm = SAD insertion more difficult
Sternomental distance
Sternal notch to tip of mandible
* Less than 12.5cm = difficult direct laryngoscopy
Define the Cervical neck movement for ease of laryngoscopy
- Extension of upper cervical spine
- Limited (less than 90 degrees)
= Difficult direct laryngoscopy
List predictors of difficult mask ventilation
- Obese (BMI over 26kg/m2)
- Beard
- Absence of teeth
- Facial abnormalities/ craniofacial syndromes
- Receding chin
- Mallampati 3-4
List predictors of difficult supraglottic airway device
- May be used as rescue plan
- Mouth opening < 2.5cm
- Intraoral and pharyngeal masses
- Obesity
- Poor dentition
First-line investigations for difficult airway
- Nasoendoscopy
- CT or MRI scan
- Ultrasound
- Plain radiographs: CXR, facial X-rays, C-spine X-ray
Monitor: SpO2, BP/P, temperature
List all basic airway management options
Simple airway maneuvers:
- Head-tilt chin-lift: when C-spine injury is NOT a concern ± combination w/ manual in-line stabilization to stabilize C-spine when jaw thrust fail to open airway
- Jaw thrust: when C-spine injury IS a concern (eg. trauma
Simple airway adjuncts:
- Oropharyngeal airway
- Nasopharyngeal airway
Basic ventilation techniques:
- Mouth-to-mouth ventilation (only if no equipment, risk of infection and poor O2 enrichment)
- Mouth-to-mask ventilation (one way valve decrease infection risk)
- Bag-valve-mask (BVM) ventilation with Ambu-Bag
Removal of underlying causes:
- Foreign body aspiration: bough, finger sweep, Heimlich maneuvers, Chest thrust, back blows
- Suction for secretions
Signs of successful ventilation
- Chest expansion
- Exhaled tidal volumes
- Presence of breath sounds
- Listen and feel for air leaks
- Pulse oximetry reading
- Capnography most accurate
Reasons for unsuccessful ventilation
Solutions for unsuccessful ventilation
Causes of unsuccessful ventilation:
- Poor mask seal
- Airway obstruction: partial or complete
- facial hair
- dentures, edentulous, sunken cheek
- obese patients
Solutions:
* 2 person, 2 hand technique
* Ask assistant to support soft tissues of cheek
* Optimize head position and triple maneuver
* Ensure no leak/occlusion in equipment/circuit
* Facial hair: aqueous gel, occlusive dressing
* Considering leaving dentures in place
* Use of oropharyngeal/nasopharyngeal airway
* Supraglottic airway device
Complications of bag mask ventilation
- Aspiration
- Lip and dental trauma
- Ocular pressure injury
- Facial injury
Nasopharyngeal airway
- Indications
- Contraindications
- Selection
- Insertion
Indications: when OPA is difficult/ contraindicated
* Can be rapidly and easily inserted blindly
* presence of gag reflex
* oral trauma
* teeth clenched
Contraindications:
Absolute
- base of skull fracture
- nasal, midface fracture
Relative
- coagulopathy
- large nasal polyps
- recent nasal surgery
- suspected epiglottitis
Selection: tip of nose to angle of mandible
Insertion: coated w/ lubricant/anaesthetic jelly beforehand → inserted along floor of naris into posterior pharynx behind tongue → rotate slightly if resistance is encountered
Oropharyngeal airway
- Indications
- Contraindication
- Selection
- Insertion
Indications:
* For use in patients without gag reflex
* Easy to insert
* Can be rapidly inserted
* Serves as a bite block
* Facilitates suction of the pharynx
Contraindications:
* Awake with gag reflex
* Oral trauma
Selection: from incisor to angle of mandible
Insertion: either insert w/ airway curving upward and turn 180o inside posterior pharynx OR insert w/ tongue depressor
List advanced airway management options
Supraglottic approach
o Supraglottic airway devices
o Endotracheal intubation
Infraglottic approach
o Cricothyroidotomy (needle, surgical)
o Tracheostomy
Endotracheal intubation
- Indications
- Positioning
- Correct insertion
Indication:
- Controlled ventilation and oxygenation
- Airway protection
- High pressure ventilation
- Prolonged postoperative intubation or mechanical ventilation
Position:
- “Sniffing” position: Flexion of the neck, extension of head, head on 7 - 9 cm pillow/firm surface, horizontal alignment of external auditory meatus and sternal notch
Insertion:
→ Tip of ETT at midpoint of trachea ≥2cm above carina → Proximal end of cuff ≥2cm below vocal cord
→ Marking at mouth 20-22cm (F) or 22-24cm (M)
Preparation for endotracheal intubation
Preparation:
* Correctly sized endotracheal tube: Generally size 8 for male adults, 7 for female
* Laryngoscope
* Oxygen source for pre-oxygenation
* Suctioning equipment
* Tapes to secure ETT, syringe to inflate cuff
* Equipment for ventilation
* Skilled assistant
* Other airway equipment to assist intubation
Assess potential difficulties (LEMON)
- 3-2-1 rule: thyromental distance <3 finger-breadths, mouth opening <2 finger-breadths, anterior jaw subluxation <1 finger-breadth
- Mallampati score
Pre-oxygenate w/ 100% O2 for ~3-5min
- Increase O2 reserve of body to increase duration of apnea without desaturation (6-7 mins)
Sedation: induction followed by paralysis
→ Induction: IV anaesthetic, eg. propofol
→ Paralysis: IV fast-acting NMB, eg. suxamethonium
Grade of laryngeal view via direct laryngoscopy
Signs to confirm ETT position and correct intubation
Direct visualization: ETT between the vocal cords or fibreoptic visualization of the tracheal rings and carina
Sustained detection of normal etCO2 on waveform capnograph (Most reliable)
Clinical signs:
* symmetrical chest rise and fall with ventilation
* breath sounds in the axillary chest wall
* absence of breath sounds over stomach
* condensation in the ETT
Complication of ETT
Complications: can occur during intubation, while tube is in place, and after
extubation
- Malpositioning: esophageal intubation, bronchial intubation, laryngeal trauma
- Physiological responses: Hypertension, tachycardia, laryngo-/bronchospasm, Intracranial/ intraocular hypertension, Negative pressure pulmonary edema
- Airway trauma: Dental damage/ dislodgement, sore throat, lacerations, dislocated mandible, laryngeal/tracheal edema and stenosis, vocal cord paralysis (hoarseness/ aspiration)
- Tracheal tube malfunction: Cuff perforation/ damage, obstruction by kinking or thick secretions, fire (polyvinyl chloride tube ignition)
Supraglottic airway device
- Uses
- Insertion
- Predictors of difficult SAD insertion
- Complications
Uses:
* For airway rescue after failed intubation and mask ventilation
* Alternative to ETT
* As a conduit for tracheal intubation eg. intubating LMA, use of flexible scope through LMA to guide ETT
Insertion:
→ Adequate depth of anaesthesia to avoid coughing, gagging etc.
→ Lubricate LMA cuff
→ Hold LMA with glottis opening facing forward
→ press cuff upward against hard palate then go backward and downward along palate until resistance is encountered
→ Inflate cuff to ~40 cmH2O
Difficult SGA insertion:
* Small mouth opening ˂ 2.5cm
* Intraoral/pharyngeal masses
* Poor dentition
* Obese
Complications:
- Dry mouth/ sore throat
- Laryngeal trauma
- Dysphonia
- Hypoglossal/ lingual nerve damage
- Pulmonary aspiration
- Gastric insufflation
- Laryngospasm
Front of neck airway access
Indications
Techniques
Limitations
Complications
Indications:
* Emergency: Can’t intubate, can’t ventilate
* Acute upper airway obstructions
* severe anatomical deformity
Techniques:
* Needle cricothyroidotomy
* Surgical cricothyroidotomy
Limitations:
- Poor CO2 elimination
- limited to ~30min use, need surgical tracheostomy afterwards
Complications:
* Prolonged execution time
* Aspiration, subcutaneous emphysema
* False placement: oesophagus, pneumothorax
* Catheter issues: Tube obstruction, infection, hemorrhage
* Barotrauma
* Late: Dysphonia, subglottic stenosis
Closed face mask
- Uses
- Bag-mask ventilation
- Pre-oxygenation prior to general anaesthetic induction
- Non-invasive ventilation for respiratory failure
- Inhalational induction of general anaesthesia
- Maintenance of general anaesthesia
Bag-valve-mask ventilation with Ambu bag
- Uses
- Ventilation
- How to apply
Uses:
* High flow oxygen and high FiO2
* Controlled positive inspiratory pressure
* Provide positive end expiratory pressure
* Augmentation of spontaneous ventilation
Ventilation rate: 8-10/min if cardiac arrest and 10-12/min if respiratory arrest
O2 enrichment W/o reservoir bag: 5-6L/min O2 can achieve FIO2 ~50%
O2 enrichment W/ reservoir bag: 5-10L/min O2 can achieve FIO2 ~80%
Useage: Adequate mask seal achieved by E-C grip; Ensure patent airway by use of airway maneouvers or airway adjuncts
Difference between RSI and routine induction for ETT
→ RSI: NMB immediately after induction → apply cricoid pressure3 **but do NOT do BVM **→ ETT insertion AFTER onset of NMB (~30s)
→ Routine: IV anaesthetic induction → BVM to establish ability to ventilate → IV NMB given for paralysis → BVM again to establish ability to ventilate → ETT insertion (if failed, can do BVM)
Outline factors that influence the choice of advanced airway
Considerations for ETT insertion:
□ If emergency (arrested or agonal state) OR unconscious, do direct intubation w/o giving drugs
□ If airway NOT predicted to be difficult, do intubation w/ rapid sequence induction (RSI)
□ If difficult airway predicted, choose a method that can maintain adequate oxygenation
→ RSI if rapid deterioration of condition
→ Attempt BVM or LMA if these are predicted to be more successful
□ If failed intubation
→ Consider alternative (eg. BVM, LMA, laryngoscopy-guided intubation) if still can oxygenate
→ One attempt at LMA and BVM ventilation if cannot oxygenate
→ NEEDLE CRICOTHYROTOMY if all else fail
