7. Airway Blocks in Context of AFOI

Question 1

What are the indications for performing an awake fibre-optic intubation?

Answer 1

1.Suspected or known difficult intubation

2. Patient with a full stomach and an anticipated difficult intubation
3. Suspected or known cervical spine injury
4. Anticipated difficult mask ventilation (e.g. morbid obesity)

Question 2

What are the contraindications to performing an awake fibre-optic intubation?

Answer 2

Patient refusal

Patient unable to co-operate

Bleeding upper airway

Allergy to local anaesthetics

Upper airway tumours with stridor
(scope may completely obstruct the
tracheal lumen or cause severe bleeding)

Question 3

What antisialogogue would you use?

Answer 3

Glycopyrronium 4–8 mcg/kg im (or iv) an hour before the procedure

Hyoscine 0,.2 mg im or

Atropine 0.3–0.6mg im

Question 4

What is the nerve supply to the nose?

Answer 4

Mainly from two sources:

1. The second division of the trigeminal nerve
   via the sphenopalatine ganglion.
   (Also supplies the superior part of the palate, uvula and tonsils.)
2. The anterior ethmoidal nerve

Question 5

What is the nerve supply to the nose?

Answer 5

Mainly from two sources:

1. The second division of the trigeminal nerve
   via the sphenopalatine ganglion.
   (Also supplies the superior part of the palate, uvula and tonsils.)
2. The anterior ethmoidal nerve

Question 6

How would you anaesthetise the nose?

Answer 6

Options include:

4% cocaine pledgets
Lidocaine spray
Nebulised lidocaine

Question 7

How is the oropharynx innervated?

Answer 7

Plexus derived from the vagus, facial and glossopharyngeal nerves

The glossopharyngeal nerve:
Exits the skull via the jugular foramen and enters the pharynx between
the superior and middle constrictor muscles of the pharynx.

Sensation to the posterior third of the tongue (lingual branch), anterior
surface of epiglottis, posterior and lateral walls of the pharynx and
tonsillar pillars.

Motor to stylopharyngeus

Question 8

How could you anaesthetise the pharynx?

Answer 8

Topical anaesthesia with 10% lidocaine spray
or gargled/nebulised 4% lidocaine

If there is still a marked gag reflex following one of the above procedures,
then a glossopharyngeal nerve block can be performed.

Question 9

Techniques for glossopharyngeal nerve block

Anterior approach

Answer 9

Internal: Anterior or posterior approach

Anterior approach

Mainly blocks the lingual branch.

Apply topical anaesthesia to the tongue.

Displace the tongue away from the side to be blocked.

A gutter forms between the tongue and teeth.

Use a spinal needle to gain an unobstructed view.

Insert the needle at the posterior ‘cul-de-sac’ of the gutter at a depth
of 0.25 – 0.5 cm and aspirate.

If air is aspirated, retract a short distance.

Inject 2 ml LA.

Question 10

Techniques for glossopharyngeal nerve block

Posterior

Answer 10

Posterior approach

A more proximal block, it blocks sensory
(pharyngeal, lingual and tonsillar branches)
and motor to stylopharyngeus.

Apply topical anaesthesia to the tongue
.
Depress the tongue.

Insert an angled needle behind the middle of the posterior tonsillar
pillar to a depth of 1 cm.

After aspiration, inject 3 ml LA.

More likely to get intravascular injection with this approach

Question 11

External

Techniques for glossopharyngeal nerve block

Answer 11

Injection deep to and behind styloid process (2–4 cm deep).

Found midway between the tip of the mastoid process and the angle
of the jaw.
Tiger country with internal carotid and jugular vessels close by.

Question 12

What is the sensory and motor supply to the larynx

Answer 12

Superior Laryngeal nerve above cords

Recurrent laryngeal nerve below

Question 13

Superior Laryngeal Nerve

Answer 13

Innervation of the laryngeal inlet is primarily from the
superior laryngeal nerve,
a branch of the vagus

The superior laryngeal nerve leaves the vagal trunk
in the carotid sheath and travels
anteriorly to the cornu of the hyoid bone.

Here, it divides to form the internal branch (sensory)
and the external branch (motor to cricothyroid muscle).

The internal branch pierces the thyrohyoid membrane and enters the
piriform fossa mucosa. It provides sensory supply to the larynx down to the
vocal cords, the base of the tongue, vallecula, aryepiglottic folds and
arytenoids.

Question 14

recurrent laryngeal nerves

Answer 14

The recurrent laryngeal nerves (from the vagus)

supply sensation below the vocal cords

and all the muscles of the larynx except cricothyroid

Question 15

How could you anaesthetise the larynx?

Answer 15

The sensory supply above and below the cords needs to be addressed.
Sensation above the cords:

Superior laryngeal nerve block
May be performed externally by injection or internally by topical
anaesthesia.

External

Internal SLN Block

Question 16

External SLN block

Answer 16

Seated or semi-recumbent patient

A wheal is raised 1 cm inferior and 2 cm anterior to the extremity of
the prominent cornua of the hyoid bone.

The needle is walked off the lower border of the hyoid bone to pierce
the thyrohyoid membrane.

2–3 ml of 2% lidocaine is injected.

The injection is repeated on the other side.

Question 17

Internal SLN block

Answer 17

Internal
Using Krause’s forceps, hold a lignocaine-soaked pledget in the
piriform fossa for 2–3 minutes on each side.
Very simple (if you can find Krause’s forceps!)

Question 18

Sensation below the cords:

Answer 18

Cricothyroid puncture

Also known as a translaryngeal block.

Will anaesthetise most of the laryngeal surface.

The cricothyroid membrane is identified and the skin overlying it fixed with
the index and thumb of the operator’s non-dominant hand.

Following disinfection and local anaesthetic infiltration to the skin, a
syringe with saline is attached to a 20-gauge cannulae and inserted through
the cricothyroid membrane.

Air is aspirated confirming laryngeal placement of the cannulae.

The needle is withdrawn and 2–3 ml of 2% lidocaine is injected.

The induced coughing aids dispersion of the local anaesthetic.

Question 19

Most common method

Answer 19

Alternatives are to use nebulised 4% lignocaine as the sole anaesthetic
technique or to ‘spray as you go’ via the bronchoscope

(probably the commonest technique for awake fibre-optic intubation).

See also Long
Case 1 ‘The one about the woman with a goitre for an emergency
laparotomy’.