Anaesthesia for ENT

Question 1

Which procedures in ENT are included in ‘ENT Endoscopy’

Answer 1

Laryngoscopy
Microlaryngoscopy (aided by operating microscope)
Esophagoscopy
Bronchoscopy

Question 2

What important preoperative issues with regards to ENT endoscopy

Answer 2

1. ? BVM
2. ? ETT with VL/DL

If answer to either question is NO
–> awake fibreoptic intubation

If answer to both is yes
—> DL/VL ok

(Consider a small dose of propofol to have a quick look)

Question 3

What are 5 methods for ventilating and oxygenating a patient for endoscopic ENT surgery

Answer 3

1. Small ETT (size 6) but cuff relatively to small and hence to tight with overinflation pressure)
2. Insufflation with catheter via trachea
   - for posterior commissure issue - inadequate ventilation + TIVA required
3. Intermittent apnoea and re-intubation (high risk)
4. Connect manual jet inflator to side port of laryngoscope - during inspiration high pressure jet of O2 is directed through glottic opening with passive expiration - monitor chest wall motion and allow sufficient time for exhalation. Requires TIVA
5. Delay and tracheostomy

Question 4

Why do BP and HR fluctuate in ENT surgery and how can this be mitigated

Answer 4

1. Elderly/smoking Hx/ETOH Hx/ –> CVS diseases
2. Series of physiologically stressful laryngoscopies and interventions separated by periods of minimal surgical stimulation.

Rx
1. Provide modest baseline anaesthesia with intermittent supplementation with short acting anaesthetics (propofol, remifentanyl, esmolol)

2. Regional nerve blocks
   - Glossopharyngeal n. block
   - Superior laryngeal n. block

Question 5

What precautions need to be taken with regard to laser airway surgery

Answer 5

1. Evacuate toxic fumes (laser plume) (can transmit microbiological diseases)
2. Eye protection
3. Prevent airway fire
   - Minimise FiO2 as close to 0.21
   - Non-flammable tube/catheters
   - ETT double cuffs one with saline to absorb thermal E
   - Wrap ETT with metallic tape (not ideal)
   - No N2O (supports combustion)
   - Limit laser intensity
   - Source of water available

Question 6

What are the preoperative considerations relevant to Nasal and sinus surgery

Answer 6

1. Pre-op nasal obstruction - difficult BVM
2. Nasal polyps associated with asthma
3. Bleeding diathesis (rich vascular supply nasal muc.)

Question 7

Describe local anaesthetic technique for nasal procedures

Answer 7

1. LA soaked gauze into nose for 10 mins
2. Supplement with submucosal injections of LA
   (Cocaine 4% or 10% or epinephrine containing soln to minimise blood loss).

Question 8

Why is cocaine used for nasal procedures and what are the possible side effects

Answer 8

–> rapidly absorbed (topical) within 30 minutes

CVS side effects

Question 9

Why is general anaesthesia often preferred for nasal procedures

Answer 9

Discomfort and incomplete block that may accompany topical anaesthesia

Question 10

What is the problem with RAE tubes and what can be done to solve this

Answer 10

North (nasal) and South (oral) facing RAE tubes have a preformed bend in the tube which might not be congruent with specific patient anatomy meaning that the bend is either in the mouth/nose or protruding excessively out of the mouth/nose.

A re-inforced tube can be bent without kinking and should be used instead of a RAE tube in these instances

Question 11

Why are NMB usually used during sinus surgery

Answer 11

There is potential for neurological and ophthalmic complications if the patient moves during sinus instrumentation

Question 12

List the techniques used to minimise blood loss during nasal/sinus surgery

Answer 12

1. Epinephrine containing LA/Cocaine to supplemental topical/SC
2. Slight head up
3. Mild degree of controlled hypotension
4. Posterior pharyngeal pack –> limit risk of aspiration of blood

ALWAYS BE PREPARED FOR MAJOR BLOOD LOSS (Particularly with resection of vascular tumours)

Question 13

What should be avoided during emergence and extubation

Answer 13

Coughing and straining –> increase venous pressure and increase postoperative bleeding

Question 14

What are three options that can be used when there are significant concerns regarding potential airway problems in a cooperative and an uncooperative patient (i.e. in head and neck cancer surgery)

Answer 14

Cooperative
- Awake direct or fibre-optic laryngoscopy

Uncooperative

• Inhalational induction (spontaneous ventilation)
• Direct/fibreoptic laryngoscopy

ELECTIVE TRACHEOSTOMY under LOCAL ANAESTHETIC prior to induction of general anaesthesia is often a prudent option

Always be prepared for emergency tracheostomy

Question 15

Which nerves are potentially at risk in anterior neck surgery

Answer 15

Superior laryngeal nerves
Recurrent laryngeal nerves
Vagus nerves

Question 16

What actions should be taken by the anaesthetist during placement of a tracheostomy

Answer 16

1. Suction ETT and hypopharynx thoroughly prior to surgical entry into the trachea
2. FiO2 < 0.3 (if diathermy is used - ask surgeon not to use diathermy near the airway)
3. Deflate cuff during dissection into the trachea and withdraw tube so that tip is immediately cephalad to the incision
4. Only remove ETT once laryngectomy tube is in place, cuff inflated and position confirmed.

Question 17

Why would an ENT surgeon request no NMB during an anaesthetic?

Answer 17

Often use direct stimulation of nerves to identify and preserve them

Question 18

Which ENT structures does the vagus nerve innervate. Name the specific nerves

Answer 18

1. SUPERIOR GANGLION
   - Sensory nerve of the external ear
2. PHARYNGEAL PLEXUS
   - Sensory nerve of the pharynx
   - Superior pharyngeal constrictor m.
3. SUPERIOR LARYNGEAL NERVE
   - Sensory nerve to larynx
   - Inferior pharyngeal constrictor
   - Cricothyroid muscle (increases voice pitch - lengthens/tightens/adducts VC)
4. RECURRENT LARYNGEAL NERVE
   - All muscles of larynx except cricothyroid
   - Phonation and glottic opening

Question 19

What results from damage to the superior laryngeal nerve

Answer 19

Hoarseness and loss of vocal volume

Question 20

What results from unilateral damage of recurrent laryngeal nerve

Answer 20

Vocal changes/hoarseness

Question 21

What results from bilateral damage to recurrent laryngeal nerves

Answer 21

Aphonia

Respiratory distress ± stridor

Question 22

Manipulation of which structure can cause autonomic instability during ENT surgery. What can be done to mitigate this

Answer 22

The stellate ganglion during radical neck dissection –> located at the level of C6/C7 anterior to vertebrae.

Infiltration of local anaesthetic into carotid sheath

Question 23

Damage to which two structures in the neck can affect the patient’s intra operative and postoperative physiology

Answer 23

1. Stellate ganglion –> Autonomic instability

2. Carotid sinus/bodies –> loss of hypoxic drive and postoperative hypertension

Question 24

What is the prominent feature of the preoperative assessment in maxillofacial reconstruction and orthognathic surgery?

Answer 24

Airway assessment

Question 25

What are methods used to minimize blood loss in maxillofacial reconstruction and rthognathic surgery?

Answer 25

1. Slight head up
2. Controlled hypotension
3. Local infiltration with epinephrine containing solutions

Question 26

What anaesthetic strategies can be employed during maxillofacial reconstruction and orthognathic surgery?during the extubation stage when there is a chance oedema and bleeding in the airway

Answer 26

1. Wait till patient is completely awake and there are no signs of continued bleeding
2. Carefully observe or leave intubated –> can attempt extubation over an endotracheal tube exchanger
3. Wire cutters always available for pts with maxillomandibular wiring
4. Always ensure throat pack is removed

Question 27

What anaesthetic agent should be avoided in tympanoplasty and why

Answer 27

N2O
–> diffuses into air filled spaces faster than N2 can be reabsorbed into the blood stream leading to expansion.
Expansion of middle ear can displace the graft

Question 28

What is the differential diagnosis for stridor and RDS in a patient post sinus surgery

Answer 28

1. Laryngospasm (blood or secretions stimulating superior laryngeal nerve)
2. Laryngeal oedema
   - Allergic drug reaction
   - Hereditary or iatrogenic angioedema
   - Traumatic intubation
3. Foreign body aspiration
4. Vocal Cord dysfunction
   - Residual muscle relaxant
   - Hypocalcaemic alkalotic tetany
   - Intubation trauma
   - Paradoxical vocal cord motion (hysterical stridor)

Question 29

With regard to airway fires, what are the components of the fire triad

Answer 29

1. Oxidizer (O2 or N2O)
2. Ignition source (laser / diathermy)
3. Fuel

Question 30

What is the immediate management of an airway fire

Answer 30

1. Stop procedure
2. Remove ETT
3. Stop flow of all gases
4. Remove sponges/other flammable material
5. Pour saline on the airway
6. Re-establish ventilation once fire is out with room air
7. Examine ETT to check no fragments were left in the trachea (consider bronchoscopy)