Principles of Ear, Nose, and Throat Surgery

ENT surgery has the anaesthetist and surgeon sharing the airway
Anaesthetic management has to adapt to surgical concerns.

40% of difficult airway cases in NAP4 were ENT

General principles for anaesthesia for ENT surgery include:

Appreciating the shared and remote airway:
- Limited access
- Casual surgical vandalism
  - Dislodgement
  - Eyes
  - Lips
  - Teeth
Use of throat packs
Good analgesia plan
Surgery may often be highly stimulating intraoperatively, but post-operative pain may be minimal.
- High dose fentanyl for major ENT surgery
- Remifentanil for procedures with low post-operative pain
  0.5-1μg/kg load, and infusion at 0.1-0.3μg/kg/min.
Smooth emergence
Straining or coughing during emergence can ↑ bleeding, disrupt repairs, or dislodge grafts.
- Deep extubation if appropriate
- Exchange to LMA
- Remifentanil at 0.1μg/kg/min until extubation
Careful preoperative assessment
- History
  - Vocal changes
    Suggests a glottic lesion.
  - Stridor
    Highly significant.
  - Dyspnoea
    Supine dyspnoea concerning for >50% laryngeal obstruction.
  - Pain
    - Ear
      Suggests supraglottic.
  - Dysphagia
    Suggests ↑ size.
- Examination
- Investigations
  - Nasoendoscopy
  - CXR
  - MRI/
  - Ultrasound
  - ABG
  - LFTs

Anaesthetic Techniques

Classify into:

Tube
- ETT
- MLT
- Laser-resistant
- Awake tracheostomy
  Consider for:
  - Critical upper airway obstruction
    Consider under LA.
  - Predicted difficult intubation
  - Failed intubation
  - Predicted difficult extubation
  - Failed extubation
Tubeless
- HFNO
  - Fire risk
  - Avoid in:
    - Hypertensive patients
    - Obese patients
    - Unwell patients
      Hypercapnoea will occur and may be problematic in long cases.
  - Techniques:
    - Apnoeic
    - Spontaneously ventilating
      - Propofol infusion and HFNO
      - Often technically difficult to achieve
- Jet ventilation
  - Supraglottic
    - Risk of missing larynx and hypoxia
  - Infraglottic
    - ↑ risk of barotrauma
    - Reduced cord movement
  - Transtracheal
Intermittent ventilation
e.g. LMA, oxygenate, remove LMA, procedure, desaturate, replace LMA, repeat…

Laryngeal Surgery

Anaesthesia for laryngeal lesions requires understanding the pathology, as this determines:

Surgical approach and technique
This dictates the:
- Potential options for anaesthetic and airway management
- Surgical requirements
  - Laser
    See laser safety.
  - Head motion/position
  - Use of nerve monitoring
    Requires avoidance of muscle relaxation.
  - Airway access
    Often airway is inaccessible during surgery.
Likelihood of difficult airway
Airway compromise is common in these patients.

Glottic Lesions

Location
- Anterior
  Usually amenable to MLTETT/ if tracheal inspection not required.
- Posterior
  Not amenable to ETT, requires either jet or apnoeic (tubeless) oxygenation.
Type of pathology
- Papilloma
  - Laser
  - Usually requires surgeon to inspect the entire bronchial tree
Surgical technique
State of airway on completion of surgery
Often worse:
- Blood
- Oedema

Subglottic Lesion

Location
- Amenability to tracheostomy
- Extent of lesion
Airway usually improved on completion of surgery

Supraglottic Lesion

Often straightforward larynx but view impeded by pathology
Often need some alternative device:
- VL
- FOI
- Awake tracheostomy
Imaging
Nasoendoscopy
Method of surgical treatment
State of airway on completion of surgery

Nasal Surgery

Topical vasoconstrictors:

May precipitate profound hypertension
Beware ischaemic heart disease.
- Best managed with short-acting vasodilators
- Consider short acting β-blockers (e.g. esmolol) in patients already β-blockaded
Cocaine
Less commonly used. Up to 2mg/kg.
Adrenaline
Commonly used. Dose will depend on current haemodynamics.

Bloodless surgical field:

Particularly important for nasal surgery as this allows easier identification of anatomy and expedites the procedure
Aim:
- 5-10° head up
- Avoid hypercarbia
- Hypotensive anaesthesia
  Combination of lower SBP and HR ~60.
  - Remifentanil TCI 3-4ng/mL usually excellent option for all of the above
  - Consider adding esmolol, hydralazine, clonidine if unable to achieve this despite higher remifentanil use

Nasal obstruction:

May be difficult o mask ventilate with a closed mouth in this patient population due to the nature of the surgery
OPA is helpful.

Airway:

Restricted access
Decide between oral RAE or flexible LMA depending on aspiration risk and comfort level with limited access
A well-fitting LMA will pool blood above and offer good protection to the airway
- Leak can be managed with switching to an alternate size or packing the mouth with a throat pack
  Leak will cause bubbles in the surgical field and be disruptive.

Analgesia:

Usually minimal analgesia requirements post-procedure

Ear Surgery

Avoidance of nitrous
Usually contraindicated to prevent distension of the middle ear, but may (at times) be requested by the ENT surgeon.