Draw a labelled diagram of larynx. Mention the nerve supply of larynx. Describe Block for awake intubation?

Nerve Supply of Larynx

The larynx is innervated by

1. Superior Laryngeal Nerve⇨external and internal branches
2. Recurrent laryngeal nerve
3. Sympathetic nerves

• The Internal Laryngeal Nerve is sensory
• The External Laryngeal Nerve is Motor
• The Recurrent Laryngeal Nerve is mixed

The Internal Laryngeal Nerve is sensory down to the vocal cord and Recurrent Laryngeal Nerve is sensory below the vocal cords with overlap of territories
All the intrinsic muscles of the larynx is supplied by the Recurrent Laryngeal Nerve except the Cricothyroid which is supplied by the External Laryngeal Nerve

AWAKE INTUBATION
Awake intubation is the mainstay os ASA's difficult airway algorithms
Advantages of Awake over Anesthetised are

1. Maintenance of Spontaneous ventilation
2. increased size and latency of the pharynx
3. relative forward placement of the base of tongue
4. posterior placement of larynx
5. Patency of the redropalatal space
6. awake state offers better sphincter tone of oesophageal sphincters

Contraindications 
Patient Refusal
Inability to cooperate
Allergy to local anaesthetics

Procedure of awake intubation

1)Patient counselling with explanation for the need of  awake airway and the techniques briefed

2)Medication to allay anxiety can be done with judicious dosing of small amounts of sedatives like           midazolm or opioids like fentanyl can be titrated,avoid poly pharmacy and reversal agent in hand

Dexmedetomidine a highly selective centrally acting alpha 2 adrenergic agonist causes sedation without respiratory depression

3)Administration of antisialogogues is important to clear airway secretions for optical instruments

4)Vasoconstriction of nasal passages if instrumentation required

5) Supplemental Oxygen by nasal cannula

6) Local Anesthetics are the cornerstone of awake airway control techniques  The areas for topical anesthesia are nasal cavity /nasopharynx,pharynx /base of  tongue,hypopharynx/larynx/trachea

The Nasal cavity is supplied by Greater and Lesser palatine from sphenopalatine ganglion  and the anterior ethmoid nerve

The Sphenopalatine Ganglion Block 

Noninvasive technique of cotton tipped applicators soaked in local anaesthetic and passed along upper border of the middle turbinate left in place for 10min

Invasive technique is by the oral approach ,needle is introduced through the greaterpalatine foramen which is palpated at the posterior lateral aspect 1cm medial to the second and third maxillary molars

Anesthetic solution of 1-2ml is injected with spinal needle at supero-posterior direction to a depth of 2-3 cms

Oropharynx is innervated by branches of vagus, facial, and glossopharyngeal

The Glossopharyngeal has three branches with sensory innervation a wide variety of techniques are involved like aerosolised local anaesthetic solution or a voluntary swish and swallow

Glossopharyngeal nerve block esp when topical techniques do not block the gag reflux

Standing opposite to the side to be blocked the operator displaces the extended tongue to the contralateral side and a 25G spinal needle is inserted into the membrane near the floor of the mouth or the posterior approach is where the needle is inserted behind the palatopharyngeal arch but the risk of carotid insertion is high

Superior Laryngeal Nerve Block is done by injecting at the local anaesthetic at the space between the thyrohyoid membrane and the pharyngeal mucosa landmark is the hyoid bone

trans tracheal injection of local anaesthetic is done with lidocaine 4ml of 2% or 4%