ENT/Airway Flashcards
Pathophysiology of stridor?
Indicates a reduction in airway diameter of >50%
Bernouilli principle - cross-sectional area of airway decreases, velocity of air increases creates low pressure in airway exacerbating airway collapse
Inspiratory vs expiratory stridor?
Inspiratory stridor = extrathoracic e.g. laryngeal obstruction (-ve pressure during inspiration worsens obstruction)
Expiratory stridor = intrathoracic (tracheobronchial obstruction) (+ve pressure during expiration reduces airway calibre)
Causes of acute stridor?
Foreign body aspiration
Infection - epiglottis, laryngitis, neck abscess
Vocal cord palsy (e.g. post head and neck surgery)
Anaphylaxis
Laryngotracheobronchitis
What are the immediate non-surgical options available for managing stridor ?
- HFNO - high FiO2, humidified, PEEP
- Nebulised adrenaline - 5-10mls of 1:1000, vasoconstrictor
- Steroid therapy - increase airway calibre, remember radius to 4th power resistance
- Heliox - reduces reynolds number, inc. laminar flow, reduce WOB but less FiO2
Advantages and disadvantages of awake fibreoptic intubation?
Awake fibreoptic intubation:
Advantages: keep pt. spont ventilating until airway secured, used when facemask ventilation or laryngoscopy likely to be v difficult (e.g. supraglottic lesions, base of tongue)
Risks: tumour may be difficult to anaesthetise, requires co-operation, difficult if pt. un-co-operative or in extremis, cork in bottle phenomenon
Advantages and disadvantages of awake videolaryngoscopy?
Advantages - allows passage of tube under direct vision, overcomes cork in bottle effect (when style/bougie removed)
Risks - requires co-operation, not suitable for base of tongue, poor MO, or supraglottic masses
Advantages and disadvantages of awake tracheostomy?
Cases where mask and intubation ventilation likely to be difficult/impossible
Patients required to lie flat, makes dyspnoea worse, may have difficult anatomy, requires ENT
Advantages and disadvantages of IV induction GA for difficult airway?
Advantages - may be only way if patient anxious/uncooperative, familiar technique for anaesthetists, can mitigate risks by pre-emptively passing cricothyroid cannula e.g. for jet
Can use HFNO for apnoeic oxygenation
Risks - risk ‘losing the airway’ as patient not spont ventilating therefore not oxygenating and ‘waking up’ risks significant hypoxia
Advantages and disadvantages of inhalational induction for difficult airway?
Advantages - historically technique of choice, theory is keeps pt. spont ventilating, and if they obstruct then no anaesthetic delivered and patient wakes
Risks - in practice, pharyngeal loss of tone results in worsening obstruction, volatile agent is unable to be expired and patient stays asleep. Need significant anaesthetic depth for airway instrumentation
How would you perform an ATI?
Pre-procedure:
- Indication
- Explanation of procedure
- Consent
- Choose best nostril
- Review FNE / CT images
Procedure:
- Positioning, Resus, IV access, Monitoring, Assistant, Drugs, Equipment
POSITION - pt sat up, facing patient
RESUS - drugs drawn up
IV access - secured
MONITORING - AAGBI standard monitoring
ASSISTANT - consider 2nd anaesthetist
DRUGS
- Resus
- Sedation, minto remi infusion or dexmedetomidine
- Lidocaine topicalisation
- Anti-siallogue
- Drugs for induction and maintanence, TIVA or volatile
EQUIPMENT
- Airway trolley including plan D
- Nasal rae tube if nasal intubation
- HFNO for apnoeic oxygenation
Nasal mucosa - co-phenelcaine
Oropharynx topicalisation 9mg/kg lidocaine toxicity, use 10%
20-30 sprays back of mouth
Can spray as go with 2% lidocaine + air, sprayed above and below cords
Get pt. to inspire, coughing is good when topicalising
Intubating trachea with scope, railroading tube, confirming within trachea above carina, confirming with ETCO2, drugs then inflate cuff
Name 4 anaesthetic considerations for an endoscopic resection of laryngeal carcinoma?
- Co-morbidities associated with smoking and alcohol (risk factors for L. cancer)
- Potential for difficult laryngoscopy
- Shared airway
- Potential for surgical laser use
2 ETTs used for laryngeal surgery?
- Microlaryngeal tube (MLT
- 4.0-5.0mm PVC tube of adult length - Flexometallic endotracheal tube (“reinforced tube”)
- Available 3.0-9.5mm
- Wire within tube allows it to bend without occluding lumen - Laster resistant endotracheal tube
- Double cuffed
- Non-flammable
- Flexible stainless steel tube
Disadvantages of conventional airways in laser surgery?
- Narrow radius = high vent pressures
- Need paediatric bougie
- Position of tube in larynx can hinder surgical access
Name 3 tubeless techniques used in laser surgery?
- Spontaneous ventilation
- Allows for assessing vocal cord
- Low flow O2 with spont vent delivered narrow catheter
- Difficult to maintain anaesthesia in adults - Jet ventilation
- Supraglottic - Transglottic - Transtracheal (cricothyroid)
- Risk of barotrauma/breath stacking
- Automatic or manual jet ventilator - Apnoeic oxygenation
- Unobstructed surgical field
- High flow nasal O2 can extend apnoeic period to 10 minutes
- Risks of hypercapnoea
Airway options in dental?
- Nasal mask
- Spont breathing with sevo
- Needs jaw thrust
- Simple uncomplicated procedures
- Needs pharyngeal pack - LMA (usually flexi)
- Longer procedures e.g. impacted teeth
- Spont or controlled
- Sometimes pharyngeal pacl - ETT
- Nasal vs. oral
- Pharyngeal pack
4 year old with stridor - differential?
Croup (laryngotracheobronchitis)
Inhaled foreign body
Acute tonsilitis
Epiglottitis
Retropharyngeal abscess
Smoke inhalational injury
Trauma
Diphtheria
Angio-oedema
Epiglotittis - anaesthetic “how to”
Pre-operative:
Call for help - Consultant anaesthetist, Consultant ENT
Usually anaesthetic/paediatric history, exam (but do not distress child)
Avoid:
- Indirect laryngoscopy
- Lateral neck x-rays
- Attempting IV access
- Moving/upsetting/changing position of child (keep sat on parents lap)
Peri-operative:
- Position on parents lap sat up
- Resus drugs drawn up
- Difficult paediatric intubation equipment
- Trained anaesthetic assistant
- Choice of induction inhalational induction spont ventilating
- IV access once child unconscious
- Induction may take longer due to airway obstruction
- Once intubated - blood cultures, swabs, IV fluids, IV antibiotics, steroids if indicated, humidifed gases
Post-operative:
- Critical care environment
- Keep intubated 2-3 days
- IV antibiotics
- Leak test
- Fibreoptic nasendoscopy by ENT
Complications of paediatric tracheostomy?
Immediate:
- Loss of airway
- Bleeding
- PTX
- Oesophageal injury
- Damage to recurrent L N
Early:
- Accidental decanulation
- Obstruction 2ndary secretions
- Bleeding
- Infection
Late:
- Granuloma formation at the stoma
- Erosion into a vessel e.g. ext. carotid
- Suprastomal collapse
- Tracheal stenosis
- Tracheo-oesophageal fistula
Midface fracture repair - principles
- Intubation may be difficult due to anatomical distortion
- Shared airway
- Oral ETT may interfere with surgical access
- Facial nerve monitoring likely to be required
Midface fracture repair - “how to”
Pre-op:
- Surgical repair usually semi-elective, allows for fasting and resuscitation
- Discussion with surgeon about type of ETT req
Intra-op:
- Extensive blood loss - 2x wide bore IV access, x-match
- Single dose NMBD for facial n. monitoring
- Nasal ETT, submental, retromolar ETT
- Throat pack
- IV dex
Post-op:
- Intermaxillary fixation (wiring vs. elastic bands), wire cutters at bedside
- Significant oropharyngeal swelling therefore HDU/ICU admission
Important components of pre-op assessment for FESS?
In addition to my usual… I would focus on
Airway - bag mask ventilation may be difficult due to nasal obstruction
Co-morbidities
- asthma/bronchiectasis/LRTI common
Severity + stability
Intercurrent URTI and implications
Drug hx
- NSAIDS - asthma trigger ?
- MAOi - topical vasocontrictors
- Antiplatelets HOLD
Day case criteria - does it meet ?
Why is it important to reduce blood loss in ENT surgery ?
- Obscures surgical field - increasing length/difficulty
- Associated with PONV (intragastric blood = emetogenic)
- Risk of aspiration e.g. on extubation
- RARE = haemodynamic instability with significant loss
Methods to reduce blood loss in FESS
NON-pharmacological methods
1. Patient positioning
- Head up 10-20deg, dec venous congestion, dec. preload 2ndary venous pooling therefore dec. arterial BP in arteries of nose
- Low PEEP (<5cmH2O) - dec venous congestion due to improved drainage
Pharmacological
- Hypotensive anaesthesia - inc. MAC/clonidine/labetalol
- Cocaine (ester L.A with NRI properties). BEWARE may cause HTN/tachycardia/arrythmias/acute angle closure glaucoma
- Phenylephrine (Co-phenylcaine Lidocaine 5% with phenylephrine)
- Oxymetazoline (a-1 agonist like phenyl, good in children)
- Corticosteroids
- TXA (anti-fibrinolytic)
Airway options for FESS surgery?
Flexible LMA
- LMA cuff offers some protection from blood/secretions
- Does not require NMBD
- Spont ventilation dec. intrathoracic pressure as avoids IPPV
Disadvantages - may not be suitable in all patients e.g. obesity, GORD, difficult airway
South-facing RAE ETT
Advantages - complete airway protection intra-op
Disadvantages - as above, high risk of endobronchial intubation
Methods to reduce retained throat pack?
It is a ‘never event’
Methods include
- Inserted by surgeon and included in ‘swab count’
- Throat pack forehead stickers
- Radiopaque thread
- Tieing to ETT
- Leave protruding from mouth
- Integrate into WHO checklist
- Not using throat pack at all
PERIOPERATIVE mx. of patient with OSA (ignore pre-op and post-op
Pre-op avoid benzo pre-meds due to resp depressant effects
INDUCTION
- Regional or local techniques prefrred over GA
- all anaesthetic agents (with exception of ketamine) reduce central respiratory drive and pharyngeal muscle tone
- Ensure adequate pre-oxygenation in sitting position (maximise FRC)
- Consider using CPAP (water’s circuit or HFNO)
- ETT preferred over LMA (inc. airway security, GORD is higher risk in OSA patients with obesity)
- Expect difficult BVM and or laryngoscopy, difficult airway trolley, oxford help, assistance
- Multi-modal analgesia as opioid sparing
- Consider desflurane due to faster emergence
- TIVA models difficult in obese
EMERGENCE
- Fully reversed NMBDs
- Sat up to maximise FRC
- Fully awake
- Commence CPAP in recovery, ideally patient’s own machine, or HFNO
HDU consider post op
Consequences of obesity hypoventilation syndrome (OHS)
RV remodelling
- Hypoxaemia causes hypoxic pulmonary vasoconstriction
- Leads to pulmonary HTN
- RV remodelling
- Inc. venous hydrostatic pressure –> peripheral oedema + hepatomegaly
Polycythaemia
- Due to hypoxaemia
TREATMENT = weight loss/exercise/bariatric sx/CPAP
Anaesthetised airway risks pulmonary aspiration
If topical anaesthesia - NBM 2hrs
If airway blocks - NBM 4hrs
Complications of Thyroid surgery
- Neck haematoma
- Hypocalcaemia
- Damage to parathyroid glands
- Perioral tingling, twitching, tetany
- Trouseaus Chovstek
- Risks laryngospasm, QT prolongation, arrythmias - Recurrent laryngeal nerve palsy
- Ischaemia/traction/transection of nerve
- Unilateral vs. bilateral palsy - Tracheomalacia
- Tracheal collapse due to erosion of tracheal cartilages caused by long-standing goitre
- Immediate re-intubation often required
Thyroid surgery - induction consideration
When no airway concerns, IV induction with paralysis and intubation using reinforced ETT
D/w surgeon re: paralysing agent and NIM tube nerve monitoring
If concern re: airway or tracheal compression then other techniques
Inhalational induction
Awake fibreoptic
Tracheostomy under L.A
Ventilation through rigid bronchoscope
Thyroid surgery - intraoperative considerations
Maintanence with volatile or TIVA
Remifentanil
- Hypotensive anaesthesia
- Reduce laryngeal reflexes therefore no further muscle relaxant required
15 deg head up to decrease venous pressure
Dexamethasone 8mg IV to reduce post op airway oedema
Haemostasis - valsalva manouvre
Analgesia
Neck haematoma evacuation mnemonic
SCOOP
Skin Exposure - remove dressings
Cut subcutaenous sutures
Open skin - push fingers into wound
Open muscle - open strap muscles to expose trachea
Pack wound
Neck haematoma management
Recognise
High flow O2
Nurse at 45 degrees
Immediate senior surgeon + anaesthetist review
Any signs of airway compromise - SCOOP if anterior neck
Prepare for intubation, expect difficult airway
What is within the posterior fossa
Most inferior to cranial fossae
Contains cerebellum, brainstem and lower cranial nerves
Comprised of
- Occipital bone postero-inferiorly
- Temporal bone anteriorly and laterally
- Sphenoid bone anteriorly and medially
Roof is tentorium cerebelli
Compact with poor compliance, small tumour = high ICP with risk of brainstem compression
What is an acoustic neuroma?
AKA vestibular schwannoma
Benign tumour of myelin-forming Schwann cells of vestibular nerve (8th)
Features:
Unilateral hearing loss, tinnitus, imbalance, unsteadiness, vertigo (VIII)
LARGE TUMOURS affect V and VII CN
Proximity to VII necessitates EMG monitoring
Posterior fossa “how to” pre-op
Usual anaesthetic assessment
+
Evaluation of cranial nerve dysfunction
Assessment for presence of raised ICP
Posterior fossa “how to” intra-op
Positioning - supine or park bench
Resus drugs drawn up
IV access secured on uppermost limb
Monitoring including art line awake if high ICP and EMG monitoring + BIS + temp + IDC
Airway = reinforced ETT
Drugs + Ex drawn up
Induction - smooth haemodynamically stable avoid CPP hypoperfusion and hypertension, high dose remi
Single dose muscle relaxant
Maintain with TIVA
Extubation smooth extubation no coughing/straining and ICP spikes
Issues specific to posterior fossa surgery
Intraoperative brainstem handling may cause cardiovascular instability, hypertension and bradycardia
Optimise physiology to maximise CPP
Avoid hypoxia
PaCO2 4.5-5.0
Temp control
Plasma glucose 4-11mmol/L
MAP >80
Obtund sympathetic response
V. emetogenic so antiemetics
What are the classic features of spinal epidural abscess and what other features may be present?
Classic triad
1. Back pain
2. Fever
3. Abnormal neurology
Other features
1. Nerve root pain
2. Motor weakness
3. Sensory deficit
4. Bowel/bladder dysfunction
4 Stages:
1. Back pain affected site
2. Nerve root pain radiating from affected area
3. Motor weakness, sensory deficit, bladder/bowel dysfunction
4. Paralysis
Causes of epidural abscess
90% Staph Aureus
Remainder strep and gram -ve anaerobes
AAGBI BEST EPIDURAL PRACTICE
Monitored by staff aware of significance and action required in response to abnormal values
Monitoring
- HR and BP
- RR
- Sedation score
- Temp
- Pain score
- Degree of motor and sensory block
What is required for venous air embolism to occur
- Source of gas
- Communication between this source and venous system
- Pressure gradient enabling movement of gas
1ml/kg rapidly embolised can be fatal
Signs of venous A.E
Depends on volume of air, rate of entrainment, patient awake/anaesthetised
Rapid entrainment
- Classic cardiovascular embolic phenomenon: tachy, hypotension, hypoxaemia
Neurological - confusion, focal signs, dec. GCS
ECG abnormalities
VAE pathophysiology
AIr lock
- Air in rv occupies it and prevents blood flow into pulmonary circulation
Inflammation in pulmonary arterioles
Small bubbles of air into RV and pulm. circ
Mico emboli in pulmonary arterioles
Paradoxical A.Emboli through patent FO may pass into arterial circ causing coronary or cerebral signs
Prevention of venous A.E
Avoiding sitting position - sitting craniotomy high risk
Raised venous pressure at operative site - iv fluid loading, +ve PEEP
Jugular venous compression has been reported
Minimising time venous circulation open to atmosphere
Minimising bubbles in IV lines
Immediate management of VAE
ABC principles, call for help
