Topical Anesthesia of Airway

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Topical Anesthesia of Airway
www.anaesthesia.co.in anaesthesia.co.in_at_gmail.c
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Points to be considered prior to the performance
of airway blocks

• Complete explanation of the reason for performing
  the airway nerve blocks, is essential
• Consider
• (a) an alternative plan, i.e the direct
  spray of LA or spray with a nebulizer
  (b) the time available (c) the patient's
  condition
• Use of appropriate sedation to maintain patient
  comfort
• These techniques should be practiced in
  nonemergency situations so that when their
  success is required for a difficult intubation
  they can be performed appropriately

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Airway anaesthesia

• Topical
• Spray
• Jel
• Injection
• nebulization
• Nerve blocks individual multiple

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Available Lidocaine Preparations
Preparation Dose
Injectable/topical solution 1 , 2,4
Viscous solution 1, 2
Ointment 2,5
Aerosol 10

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Systemic Absorption and Toxicity

• Amount of LA absorbed varies
• Systemic absorption of topically applied
  lidocaine is limited
• 5 mcg/ ml , toxic limit of blood lidocaine
• Chinn and colleagues found plasma lidocaine
  levels of 0.44 µg/mL after inhalation of 400 mg
  of nebulized lidocaine
• Baughman and associates found that patients
  breathing 4 mg/kg aerosolized lidocaine developed
  plasma levels of less than 0.5 µg/mL
• Oral lidocaine produced even lower plasma levels
  because much of the dose is swallowed subjected
  to first-pass metabolism by the liver
• Swallowed lidocaine in the setting of topical
  airway anesthesia can cause nausea and vomiting

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Systemic Absorption and Toxicity

• Lidocaine applied directly to the trachea and
  bronchi results in higher plasma levels
• Viegas and Stoelting found plasma levels of 1.7
  µg/mL 9 minutes after tracheal installation of 2
  mg/kg lidocaine
• Sutherland and Williams in their study found that
  despite a total dose of lidocaine (5.3 2.1
  mg/kg), the mean peak arterial plasma lidocaine
  concentration was low (0.6 2.1 µg/mL)
• Gargling of large volumes (0.3 mL/kg) of 2
  lidocaine may be associated with peak lidocaine
  concentrations approaching a potentially toxic
  level

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British Thoracic society guidelines on FOB

• Total dose of lidocaine should be limited to 8.2
  mg/kg in adult pts
• Take extra care in elderly pts with liver,
  cardiac impairment
• Minimum amount of lidocaine necessary should be
  used when installed through FOB
• Thorax 200156 (suppl 1)

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Predominant nerve supply of airway
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Sensory innervations of airway
Anterior ethmoidal nerve Anterior 2/3 of nasal septum Lateral wall of nose
Sphenopalatine N Posteroir 1/3 of septum Floor of nose
Glossopharyngeal N Posterior 1/3 of tongue Posterior lateral pharyngeal wall Anteror surface of epiglottis
Internal br of superior laryngeal N Larynx includ. Vocal cords
Recurrent laryngeal N Below the level of vocal cords trahea
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Nasal cavity and nasopharynx

• Plethora of sensory fibers
• Multiple origins
• Topical application the best and safe
• Nerve blocks
• Sphenopalatine N
• Anterior ethmoidal N

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Method of packing nasal cavity
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Atomizer
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Sphenopalatine Ant Ethmoidal N block
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Oropharynx

• Vagus, facial, glossopharyngeal N
• Topical anaesthesia sufficient in majority
• Gag reflex difficult to suppress by topical alone

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Gag reflex

• Deep ,sub mucosal pressure receptors
• Postrerior 1/3 of tongue
• Gag happens more on oral intubation
• Glossopharyngeal nerve (GPN) the afferent arc

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Glossopharyngeal nerve block
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GPN block
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GPN block
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Clinical Tips

• The use of a tongue blade facilitated by
  application of a topical LA to mouth
• If air is aspirated, needle needs to be withdrawn
  
• If blood is aspirated, it is arterial (carotid
  artery), the needle is too posterior and too
  lateral. It needs to be redirected medially

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Anesthesia of Larynx

• Topical spray
• Atomiser
• Spray as you go
• Transcricoid injection Nebulized
  lidocaine
• Superior laryngeal nerve block

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Innervations of Larynx
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SLN block

• External approach
• Cornu of hyoid
• Cornu of thyriod
• Thyroid notch
• Internal approach
• piriform fossa

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SLN block Hyoid landmark
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Superior laryngeal nerve block- thyroid cornu as
landmark
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Clinical tips

• Caution not to insert the needle into the thyroid
  cartilage, injection of LA into vocal cords
  cause edema
• If air is aspirated, the needie pierced laryngeal
  mucosa to be retrieved
• If blood is aspirated (superior laryngeal artery
  or vein), needle to be redirected more
  anteriorly
• For evaluation of vocal cord movement, only the
  internal laryngeal nerve needs to be blocked
• For awake intubation, SLN and RLN need to be
  blocked

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SLN block piriform fossa
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SLN block Piriform fossa
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Trachea and vocal cords

• Translaryngeal injection
• Spray as you go
• Labats technique

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Cricothyroid membrane
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Technique of transcricoid injection
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Transcricoid injection
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Clinical tips

• Pt needs to be informed that the injection of LA
  solution make him or her cough
• Contraindicated in patients with unstable neck
• During the block, pt should not talk, swallow, or
  cough
• Catheter left in place until the intubation is
  completed for injecting more LA if necessary to
  decrease the likelihood of subcutaneous emphysema

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Spray as you go

• Non invasive
• Useful in pts at risk of aspiration
• Injecting LA through suction port of FOB
• Wait 30- 60 sec before advancing to deeper
  structure and repeat the maneuver
• Two methods oxygen spray technique Cathet
  er technique

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Oxygen spray technique

• Attach three-way stopcock to suction port
• Connect oxygen tubing with flow_at_2-4 l /min
• Through other port of 3 way inject LA
• Advantages high Fio2 delivery clean
  lens disperse mucous away aids
  innabulizing LA

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Catheter technique

• Pass a angiographic or epidural catheter into
  suction port of FOB
• Till it project 5 mm beyond FOB lens
• Inject LA through proximal connection
• Allows accurate placement of LA

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Nebulizing LA

• Safe, non invasive technique
• Useful in pts with unstable neck, ?IOP ICP
• Needs pts cooperation
• 5ml of 4 lidocaine _at_oxygen flow of 6L/min,
  ultrosonic nebulizer over 10- 15 min period
• O2 flow lt 6L/min yields droplet size of 30- 60
  microns

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