Awake Fibre-Optic Intubation (AFOI)

Link: bjaceaccp.mku015.full.pdf

Indications

Difficult Intubation

• Known previous difficult intubation
• Arthritis affecting neck mobility or neck stability: Rheumatoid arthritis; ankylosing spondylitis
• Infection: Dental abscess; Ludwig’s angina; epiglottitis; croup
• Tumours: Tongue, larynx or thyroid. (Caution in laryngeal tumours causing stridor with small diameter for ventilation - scope may cause complete obstruction)
• Iatrogenic: Radiotherapy to mouth/neck; previous airway surgery; previous neck surgery e.g. fusion
• Trauma: unstable cervical spine fracture; facial fractures, airway oedema, airway burns
• Congenital: Pierre-Robin, Treacher-Collins, Klippel-Feil, Down’s and Goldenhar’s syndromes
• Obesity
• Acromegaly
• Predicted difficult intubation using pre-operative airway assessment tools e.g. Mallampati 3-4; Thyromental distance <6.0cm, Sternomental Distance <12.5cm (though these have poor correlation with difficult laryngoscopy)

Difficult mask ventilation

• Previous difficult mask ventilation
• Obesity
• Edentulous
• Beards
• Obstructive sleep apnoea/snoring

Remember to record grade at direct laryngoscopy in chart in case of emergency re-intubation.

Sedation

Maintenance of spontaneous breathing paramount.

Oversedation can cause airway obstruction, respiratory depression and apnoea.

Second anaesthetist should be responsible for administrating sedation and monitoring the patient.

Midazolam boluses 0.5 - 1mg (not exceeding 0.05mg/kg) with fentanyl boluses up to 1.5mcg/kg

Remifentanil TCI alone titrated to effect (usually 3-5mcg/ml)

Remifentanil can be used in combination with midazolam or propofol, (though many advocates of its use advise against using it in combination therapy). Propofol TCI when used with remifentanil should not be in excess of 1mcg/ml.

Propofol TCI as the sole agent may cause both under and oversedation. Effect site concentrations of >3mcg/ml are associated with increased likelihood of oversedation.

Technique

Practicalities

• Either in front of or behind patient. Advantages of face-to face technique: ability to sit the patient up, less bending of the fibreoptic scope, verbal and facial expression encouragement from the front.

Nasal vs Oral

• Nasal technique usually easier and less stimulating for patient. Ask patient to prognathate jaw or stick out tongue to assist passage. If the scope gets saliva/mucus on the tip, ask patient to swallow.
• Oral technique may be required if nasal anatomy is abnormal / obstructed or nasal haemorrhage is a large risk.

“The Nasal Run” Anatomy

• Septum - Floor of Nose - Inferior Turbinate /meatus - Middle Turbinate / meatus - Nasopharynx - Eustachian cushions - Posterior pharyngeal wall - Soft palate - Uvula - Epiglottis - Pyriform fossa - Laryngeal structures - Tracheal rings - Carina
  Link: watch?v=YSaIUTbusqE

Topicalisaion

• Maximum dose topical lignocaine is 9mg per kg.
• There are many different techniques described for awake nasal FOI and this is the one currently employed at the Bristol Royal Infirmary. It is used to fully topicalise the airway for a nasal intubation and does not require adjuvant sedation, but this may be used to alleviate patient anxiety.
  • Glycopyrollate 3mcg/kg IM/IV 30 minutes pre-AFOI
  • 2 putts xylometazoline 0.1% to each nostril
  • 200mg 4% lignocaine nebuliser (Assumed 75% lost therefore 50mg counted)
  • Inspect target nostril and select
  • 2.5mls 5% lignocaine with 0.5% phenylephrine (co-phenylcaine) to single nostril (125mg)
  • 4 putts 10% lignocaine to oropharynx (40mg)
  • SAYGO (Spray As You GO) up to 9mg/kg total via epidural catheter using 4% lignocaine. SAYGO dose for 70kg (630mg)=630-215=415mg or 10.4ml

Regional Anaesthesia

Link: 3022-regional-topical-anesthesia-for-endotracheal-intubation.html

• Nasal cavity innervated by greater and lesser palatine nerves (from maxillary branch of Trigeminal nerve CN V2) innervating the nasal turbinates and most of the septum; and anterior ethmoidal nerve arising from the ophthalmic branch of Trigeminal (CN V1) innervating the nares and anterior third of the septum.
• Oropharynx innervated by the Vagus (CN X) and Glossopharyngeal (CN IX)
  • Vagus Nerve: Internal branch of superior laryngeal nerve provides sensory innervation to the base of the tongue, posterior epiglottis, aryepiglottic folds and arytenoids. Recurrent laryngeal nerve provides sensory innervation of the vocal folds and trachea and motor function of all intrinsic laryngeal muscles except cricothyroid (innervated by external branch of superior laryngeal nerve)
    • Superior Laryngeal Nerve
      • Bilateral injections at the level of the greater cornu of the hyoid bone (see link in “Regional Anaesthesia” for pictures and detailed technique)
    • Recurrent Laryngeal Nerve
      • Transtracheal block: patient supine, head extended. Identify cricothyroid membrane. LA to overlying skin, 22G needle on a 5 or 10ml syringe with 4ml 4% lignocaine passed perpendicular to taxis of trachea with continuous aspiration. Needle advanced until air aspirated, instillation of LA resulting in coughing and dispersion of LA.
  • Glossopharyngeal Nerve: provides sensory innervation to posterior third of the tongue, vallecula, anterior surface of epiglottis (lingual branch), walls of pharynx (pharyngeal branch) and tonsils (tonsillar branch)
    • The Glossopharyngeal nerve is most easily blocked where it crosses the palatoglossal arch
    • Can be blocked by topical spray, direct contact of soaked pledgets or infiltration by injection
    • Intra-oral approach - 22g needle used to place 5ml of local anaesthetic subucosally at the caudal aspect of the posterior tonsillar pillar (palatopharyngeal fold) after aspiration for blood (close proximity to carotid artery)
    • External approach (peristyloid): patient placed supine, line drawn between angle of mandible and mastoid process, palpate styloid process just posterior to angle of jaw along this line. Inject posteriorly off the styloid process 5-7mls local anaesthetic after careful aspiration.

Asleep Fibre-Optic intubation

Indications: Known easy ventilation and difficult intubation; to decrease manipulation of neck; to avoid dental trauma; for training

Nasal airways should receive a vasoconstrictor (e.g. co-phenylcaine)

Assistant should provide jaw thrust