Airway regional Airway regional anesthesia for awake anesthesia for awake fiberoptic intubationfiberoptic intubation

From Regional Anesthesia and Pain Medicine, Vol 27, No (March-AFrom Regional Anesthesia and Pain Medicine, Vol 27, No (March-April), 2002: pp 180-192pril), 2002: pp 180-192

by R2 by R2 黃信豪黃信豪

Introduction (1)Introduction (1)

Providing anesthetic care to the Providing anesthetic care to the patient with a difficult airway keenly patient with a difficult airway keenly interests anesthesiologists.interests anesthesiologists.

The difficult airway often provokes The difficult airway often provokes much anxiety and trepidation.much anxiety and trepidation.

Introduction (2)Introduction (2)• Difficult airways arise from multiple causesDifficult airways arise from multiple causes::1.1. ssmall mouth mall mouth 2.2. Receding jawReceding jaw3.3. Reduced mouth opening due to radiation therapyReduced mouth opening due to radiation therapy4.4. Jaw fractureJaw fracture5.5. Previous head and neck surgeryPrevious head and neck surgery6.6. Difficulty in neck extension due to prior cervical fusion or advanced Difficulty in neck extension due to prior cervical fusion or advanced

osteoarthritisosteoarthritis7.7. Neck extension is contraindicated in patients with unstable cervical Neck extension is contraindicated in patients with unstable cervical

spines due to fx., rheumatoid arthritis, Down syndrome, etc.spines due to fx., rheumatoid arthritis, Down syndrome, etc.8.8. Patients who cannot be intubated using direct laryngoscopy due to Patients who cannot be intubated using direct laryngoscopy due to

anatomical variations, even though their airway exam appears noranatomical variations, even though their airway exam appears normal.mal.

Introduction (3)Introduction (3)

In the situation where the airway must bIn the situation where the airway must be controlled and anesthesia must be delie controlled and anesthesia must be delivered via an endotracheal route, intubatvered via an endotracheal route, intubation through the use of a flexible fiberoptiion through the use of a flexible fiberoptic bronchoscope is a commonly chosen c bronchoscope is a commonly chosen methodmethod

Innervation of the AirwayInnervation of the Airway

The airway is divided into:The airway is divided into:

1.1. Nasal cavitiesNasal cavities

2.2. Oral cavitiesOral cavities

3.3. Pharynx ( consisting of the naso-, Pharynx ( consisting of the naso-, oro-, and hypopharynx)oro-, and hypopharynx)

4.4. LarynxLarynx

5.5. Trachea Trachea

Innervation of the Airway – Innervation of the Airway – NoseNose

The nasal cavity is entirely innervated by fibers garriThe nasal cavity is entirely innervated by fibers garried by branches of the ed by branches of the trigeminal nervetrigeminal nerve..

a.a. Ant. Parts of the nasal cavity and the septum – ant. ethmoidal Ant. Parts of the nasal cavity and the septum – ant. ethmoidal nerve ( a br. of the ophthalmic nerve)nerve ( a br. of the ophthalmic nerve)

b.b. The remaining parts of the nasal cavity and the septum – br. of The remaining parts of the nasal cavity and the septum – br. of the maxillary nerve, including lateral posterior superior, inferiothe maxillary nerve, including lateral posterior superior, inferior posterior, and nasopalatine nervesr posterior, and nasopalatine nerves..

These branches are relayed through the These branches are relayed through the sphenopalsphenopalatine ganalionatine ganalion which is situated in the pterygoid fos which is situated in the pterygoid fossa lateral to the sphenopalatine foramen at the level sa lateral to the sphenopalatine foramen at the level of the crest of the superior turbinateof the crest of the superior turbinate

Innervation of the Airway – Innervation of the Airway – pharynxpharynx

Mainly innervated by Mainly innervated by glossopharyngeal glossopharyngeal nervenerve

a.a. Visceral fibers – posterior third of the tongue, Visceral fibers – posterior third of the tongue, the fauces and tonsillae, epiglottisthe fauces and tonsillae, epiglottis

b.b. Special visceral sensation – posterior third of tSpecial visceral sensation – posterior third of the tongue and soft palate he tongue and soft palate

c.c. Sympathetic fibers – derived form the carotid Sympathetic fibers – derived form the carotid plexus and the cervical sympathetic trunkplexus and the cervical sympathetic trunk

d.d. Efferent motor fibers – innervate the stylophaEfferent motor fibers – innervate the stylopharyngeus muscle and join the pharyngeal plexuryngeus muscle and join the pharyngeal plexus. s.

Innervation of the Airway – Innervation of the Airway – larylarynx (1)nx (1)

The The superior laryngeal nervesuperior laryngeal nerve dividing i dividing into internal and external branch.nto internal and external branch.

a. internal br. – a. internal br. – through a foramen in the thyrothrough a foramen in the thyrohyoid membrane and provides visceral sensorhyoid membrane and provides visceral sensory and secretomotor innervation to the larynx ay and secretomotor innervation to the larynx above the true cords.bove the true cords.

b. external br. – b. external br. – supplies with motor fibers of tsupplies with motor fibers of the cricothyroid muscle.he cricothyroid muscle.

Innervation of the Airway – Innervation of the Airway – larylarynx (2)nx (2)

Recurrent laryngeal nerveRecurrent laryngeal nerve a.a. providing both structures with fibers for visceral providing both structures with fibers for visceral

sensation, motor and secretomotor innervation, sensation, motor and secretomotor innervation, and sympathetic branches.and sympathetic branches.

b.b. it enters the larynx by passing the lower border oit enters the larynx by passing the lower border of the inferior constrictor m. of pharnyx.f the inferior constrictor m. of pharnyx.

c.c. it supplies all muscle of the larynx except cricothit supplies all muscle of the larynx except cricothyroid and conveys visceral sensation to the cords yroid and conveys visceral sensation to the cords and infraglottic regions.and infraglottic regions.

d.d. it is the motor nerve of all intrinsic muscles of the it is the motor nerve of all intrinsic muscles of the larynx except the cricothyroid muscle. larynx except the cricothyroid muscle.

The airway reflexesThe airway reflexes

The aforementioned nerves participate in severThe aforementioned nerves participate in several brainstem-mediated reflex arcs.al brainstem-mediated reflex arcs.

1.gag reflex1.gag reflex – – triggered by mechanical and chemical stimulatriggered by mechanical and chemical stimulation of areas innervated by the glosso-pharyngeal nerve, and tion of areas innervated by the glosso-pharyngeal nerve, and the efferent motor arc is provided by the vagus nerve and its the efferent motor arc is provided by the vagus nerve and its branches to the pharynx and larynx.branches to the pharynx and larynx.

2.glottic closure reflex2.glottic closure reflex – – elicited by selective stimulation elicited by selective stimulation of the of the superior laryngeal nervesuperior laryngeal nerve, and efferent arc is the , and efferent arc is the recurrrecurrent laryngeal nerveent laryngeal nerve.– exaggeration of this reflex is called .– exaggeration of this reflex is called larylaryngospasm.ngospasm.

3.cough3.cough – – the cough receptors located in the larynx and tracthe cough receptors located in the larynx and trachea receive afferent and efferent fibers form the hea receive afferent and efferent fibers form the vagus nerve.vagus nerve.

Preparation of the patient Preparation of the patient

ExplanationExplanation

SedationSedation

Anti-sialagoguesAnti-sialagogues

Explanation Explanation

1.1. The reasons for proceeding with an The reasons for proceeding with an awake fiberoptic intubationawake fiberoptic intubation

2.2. The potential complicationsThe potential complications

3.3. The type of airway anesthesia that The type of airway anesthesia that will be providedwill be provided

4.4. Possible alternatives to the proposed Possible alternatives to the proposed anestheticanesthetic

SedationSedation

Adequate sedation is important and Adequate sedation is important and advantageous in both the advantageous in both the anesthetizing of the airway as well as anesthetizing of the airway as well as during the intubation.during the intubation.

A calm and comfortable patient is A calm and comfortable patient is much more likely to cooperate with the much more likely to cooperate with the anesthesiologist during the procedures.anesthesiologist during the procedures.

Agents used to produce sedation Agents used to produce sedation generally fall into 2 group: generally fall into 2 group: benzodiazepines and opioids.benzodiazepines and opioids.

About BenzodiazepinesAbout Benzodiazepines

Advantages:Advantages:1.1. Significant sedation and amnesiaSignificant sedation and amnesia2.2. Prevent seizure activity in the event of local aPrevent seizure activity in the event of local a

nesthetic toxicitynesthetic toxicity.. DisadvantagesDisadvantages::1.1. Produce unconsciousness Produce unconsciousness 2.2. Patients can not be cooperativePatients can not be cooperative.. MidazolamMidazolam has much to recommend due to has much to recommend due to

quick onset, fairly short duration of action, aquick onset, fairly short duration of action, and lack of pain with injection.nd lack of pain with injection.

About OpioidsAbout Opioids

AdvantagesAdvantages::1.1. Providing analgesia Providing analgesia 2.2. Can help blunt airway reflexes, especially coughing.Can help blunt airway reflexes, especially coughing. DisadvantagesDisadvantages::1.1. It do not provide amnesia It do not provide amnesia 2.2. Can cause significant respiratory depression.Can cause significant respiratory depression. FentanylFentanyl,, with its relative hemodynamic st with its relative hemodynamic st

ability, low cost, and familiarity to most aneability, low cost, and familiarity to most anesthesiologists, is frequently used. Small dossthesiologists, is frequently used. Small doses(0.5~2 mcg/kg) are suggestted.es(0.5~2 mcg/kg) are suggestted.

The antagonists of sedation The antagonists of sedation agentsagents

Naloxone Naloxone : 0.04~0.4 mg. For opioid-depe: 0.04~0.4 mg. For opioid-dependent patients, as its use can precipitate ndent patients, as its use can precipitate withdrawal.withdrawal.

FlumazenilFlumazenil : up to 5 mg. It may be associ : up to 5 mg. It may be associated with the production of seizures.ated with the production of seizures.

Anti-sialagoguesAnti-sialagogues

Decreasing oral secretions will aid in the Decreasing oral secretions will aid in the placing and effectiveness of topical agenplacing and effectiveness of topical agents.ts.

Fiberoptic intubation is much easier if exFiberoptic intubation is much easier if excess secretions are not obscuring the opcess secretions are not obscuring the operator’s view.erator’s view.

For these purpose, For these purpose, glycopyrrolateglycopyrrolate is the is the one that is most commonly used due to ione that is most commonly used due to its lack of CNS effects and relatively lessets lack of CNS effects and relatively lesser likelihood of producing tachycardia.r likelihood of producing tachycardia.

Local anestheticsLocal anesthetics

There are three most often used local aThere are three most often used local anesthetic with or without the use of vasnesthetic with or without the use of vasoconstrictors:oconstrictors:

1.1. CocaineCocaine2.2. BenzocaineBenzocaine3.3. LidocaineLidocaine4.4. vasoconstrictorsvasoconstrictors

Local anesthetics – cocaine Local anesthetics – cocaine

Unique in having intrinsic vasoconstrictUnique in having intrinsic vasoconstrictor properties.or properties.

It can provide both anesthesia and can hIt can provide both anesthesia and can help control the bleeding that frequently elp control the bleeding that frequently accompanies instrumentation of the nasaccompanies instrumentation of the nasal passages.al passages.

Possible adverse effects: tachycardia, hyPossible adverse effects: tachycardia, hypertension, dysrhythmias, and seizurespertension, dysrhythmias, and seizures

Local anesthetics – benzocaine Local anesthetics – benzocaine

A water-insoluble ester that is frequently used A water-insoluble ester that is frequently used in a 20% spray to produce anesthesia in mucoin a 20% spray to produce anesthesia in mucous membranes.us membranes.

Advantages: 1. available in commercially prepAdvantages: 1. available in commercially prepared aerosol applicator; 2. easy to apply to the ared aerosol applicator; 2. easy to apply to the oral mucosa; 3. produces anesthesia in 15 to 3oral mucosa; 3. produces anesthesia in 15 to 30 seconds.0 seconds.

Disadvantages: 1. short duration (5~10 mins); Disadvantages: 1. short duration (5~10 mins); 2. associated with the production of methem2. associated with the production of methemo-globinemia after as little as a total of 4 secono-globinemia after as little as a total of 4 seconds of spraying. ds of spraying.

Local anesthetics – lidocaine Local anesthetics – lidocaine

The most widely used local anesthetic in the woThe most widely used local anesthetic in the world.rld.

Advantages:Advantages: 1.ready availability; 2.relatively low 1.ready availability; 2.relatively low CNS and cardiac toxicity; 3.quick onset; 4.clinicaCNS and cardiac toxicity; 3.quick onset; 4.clinically useful duration of action (30-60 mins for topilly useful duration of action (30-60 mins for topical application and 1 to 2 hours after infiltratiocal application and 1 to 2 hours after infiltration).n).

Disadvantages:Disadvantages: 1.toxic plasma levels (>5 mcg/m 1.toxic plasma levels (>5 mcg/ml) can be reached when moderate amounts of hil) can be reached when moderate amounts of high concentration solutions are used; 2.caution gh concentration solutions are used; 2.caution must be used in patients with hepatic dysfunctimust be used in patients with hepatic dysfunction.on.

Local anesthetics – Local anesthetics – vasoconstrictors vasoconstrictors

The advantages of vasoconstrictors The advantages of vasoconstrictors with local anesthetics:with local anesthetics:

1. to prolong the duration of nerve 1. to prolong the duration of nerve blocksblocks

2. causes mucosal vasoconstriction, 2. causes mucosal vasoconstriction, which improves visualization during which improves visualization during the procedure and helps limit the procedure and helps limit bleeding.bleeding.

Topical anesthesiaTopical anesthesia

SprayingSpraying

Direct applicationDirect application

Topical anesthesia: direct Topical anesthesia: direct application (1)application (1)

If nasal intubation is planned, 2 methods of aIf nasal intubation is planned, 2 methods of applying local anesthetics are popular:pplying local anesthetics are popular:

1.1. Cotton-tipped swabs soaked in either lidocaiCotton-tipped swabs soaked in either lidocaine or cocaine and placed superiorly and postne or cocaine and placed superiorly and posteriorly in the nasopharynx. Then left for seveeriorly in the nasopharynx. Then left for several minutes to block the branches of the ethral minutes to block the branches of the ethmoidal and trigeminal nerves.moidal and trigeminal nerves.

2.2. Coating a nasal airway with viscous lidocaine Coating a nasal airway with viscous lidocaine mixed with a vasoconstrctor.mixed with a vasoconstrctor.

Topical anesthesia: direct Topical anesthesia: direct application (2)application (2)

Gargling – Gargling – not often cover the larynx or trachnot often cover the larynx or trachea adequatelyea adequately..

Aspiration – Aspiration – a simple, safe, and effective meta simple, safe, and effective method of anesthetizing the upper airway.hod of anesthetizing the upper airway.

Indirect laryngoscopy and Fiberoptic brIndirect laryngoscopy and Fiberoptic bronchoscope – onchoscope – for hypopharynx structure anfor hypopharynx structure anesthetized.esthetized.

Nerve blocks (1)Nerve blocks (1)

Often more difficult to perform, and Often more difficult to perform, and carry a higher risk of complications carry a higher risk of complications than the above mentioned methods.than the above mentioned methods.

The common complications of nerve The common complications of nerve blocks are: bleeding, nerve damage, blocks are: bleeding, nerve damage, and intra-vascular injection.and intra-vascular injection.

Nerve blocks (2)Nerve blocks (2)

There are 3 blocks used for upper airway There are 3 blocks used for upper airway anesthesia:anesthesia:

1.glossopharyngeal block – for oropharny1.glossopharyngeal block – for oropharnyx.x.

2.superior laryngeal block – larynx above t2.superior laryngeal block – larynx above the cords.he cords.

3.translaryngeal block – larynx and trache3.translaryngeal block – larynx and trachea below the cords.a below the cords.

Glossopharyngeal blockGlossopharyngeal block

There are two way to approach:There are two way to approach:1.intra-oral – need enough mouth opening1.intra-oral – need enough mouth opening2.peristyloid – require the ability to distinguish the bony 2.peristyloid – require the ability to distinguish the bony

landmarkslandmarks.. For both approaches, careful aspiration for bloFor both approaches, careful aspiration for blo

od must be carried out prior to injection becauod must be carried out prior to injection because the glossopharyngeal nerve is closely associse the glossopharyngeal nerve is closely associated with the internal carotid a. in these locatiated with the internal carotid a. in these locations and even a very small amount of local aneons and even a very small amount of local anesthetic can cause seizures.sthetic can cause seizures.

Superior laryngeal blockSuperior laryngeal block

Performing this block requires some degPerforming this block requires some degree of neck extension.ree of neck extension.

Need the ability to identify the greater cNeed the ability to identify the greater cornu of the hyoid bone and superior corornu of the hyoid bone and superior cornu of the thyroid cartilage.nu of the thyroid cartilage.

The hyoid bone can be easily fractured if The hyoid bone can be easily fractured if excess pressure is applied.excess pressure is applied.

Translaryngeal blockTranslaryngeal block

This is more correctly described as a method oThis is more correctly described as a method of topically applying local anesthetic to the tracf topically applying local anesthetic to the trachea and larynx.hea and larynx.

The coverage of this method is spotty and is mThe coverage of this method is spotty and is most often inadequate for fiberoptic intubation.ost often inadequate for fiberoptic intubation.

The method requires access to the ant. neck aThe method requires access to the ant. neck and some extension of the head, so that the cricnd some extension of the head, so that the cricothyroid membrane can be identified.othyroid membrane can be identified.

Thank you for your Thank you for your attention !!attention !!