ENT Anesthesia

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Level of the larynx in the adult?
Pedi?
- Adult= C4-6
- Pedi= C3-5
How many cartilages form the larynx?

9
Larynx arterial blood supply

subclavian artery to inferior thyroid artery to inferior laryngeal artery
Larynx venous blood drainage

inferior laryngeal vein to brachiocephalic vein to SVC
3 single cartilages of the larynx

epiglottic, thyroid, cricoid
3 paired cartilages of the larynx

arytenoids, corniculate, cuneiform
What forms the Adam's apple?
- thyroid cartilage
- largest of the laryngeal cartilages
Thyrohyoid membrane

Attaches thyroid cartilage to the hyoid bone
Narrowest part of the pedi airway

cricoid cartilage
cricothyroid ligament

Attaches cricoid cartilage to the thyroid ligament
First cartilage seen on DL

epliglottic
List the following structures from cephalad to caudad: cricotracheal ligament, thyroid cartilage, 1st tracheal ring, thyrohyoid membrane, cricoid cartilage, cricothyroid membrane, hyoid bone
- hyoid bone
- thyrohyoid membrane
- thyroid cartilage
- cricothyroid membrane
- cricoid cartilage
- cricotracheal ligament
- 1st tracheal ring
Where is a trach usually placed?
- Mid way btw the thyroid notch and the suprasternal notch
- A vertical incision is made thru the 2nd and 3rd tracheal rings with the thyroid isthmus divided and retracted
Narrowest part of adult airway

glottis
Position of the rims glottidis
-resting
-forced respiration
-phonation
- resting= narrow and wedge shaped
- forced respiration= wide and kite shaped
- phonation= slit like as VC are closely approximated
rima glottidis

opening btw the VC
What are the 3 functions of the larynx?
- protect airway
- respiration
- vocalization
How does the larynx protect the airway?
- Involuntary reflex function
- glottis closes by a reflex activated by swallowing
- primitive reflex elicited by stimulation of the superior laryngeal nerve
Function of the extrinsic laryngeal muscles

move the larynx as a whole
extrinsic laryngeal muscles
how many?
2 main groups?
- 8
- infrahyoid and suprahyoid
function of the infra hyoid laryngeal muscles

depress hyoid and larynx
function of the supra hyoid laryngeal muscles

elevate hyoid and larynx
function of the intrinsic muscles of the larynx
- move laryngeal parts
- make changes in length and tension of the VC
- open and close the glottis essentially
VC should be ____ during swallowing and ____ during inspiration
- closed
- open
4 classifications of intrinsic laryngeal muscles
- adductors and abductors
- sphincters
- tensors
- relaxers
All but one of the _____ laryngeal muscles are supplied by the _____.
- intrinsic
- RLN
Only the ______ is innervated by the external laryngeal nerve. All the other intrinsic muscles are supplied by the ____.
- cricothyroid
- RLN
The RLN is a branch of what CN?

10th CN, vagus
Major tensor intrinsic laryngeal muscles
- cricothyroid muscles
- tense and elongate the VC, this causes voice pitch to rise
Abductor intrinsic laryngeal muscle
- posterior cricoarytenoid
- open VC by widening the rims rims
Major adductor intrinsic laryngeal muscle
- lateral cricoarytenoid
- close VC
- work with transverse arytenoid muscles
- air gets pushed thru rims glottides to cause vibration of vocal ligaments and to cause phonation
The transverse arytenoid muscles cause

adduction, work with the lateral cricoarytenoid muscles
Thyroarytenoid muscle function
- relaxer
- relax VC and lower the voice
intrinsic muscles that fall into the category of sphincters
- lateral cricoarytenoid
- oblique arytenoids
- transverse arytenoids
- aryepiglottic muscles
What nerves supply the larynx?

Vagus, RNL, and superior LN
What is the only intrinsic laryngeal muscle NOT innervated by the RNL?

the cricothyroid muscle
What supplies sensory innervation of larynx down to the VC?

Internal branch of the superior LN
Function of the external branch of the superior laryngeal nerve
- motor
- innervates cricothyroid muscle and inferior pharyngeal muscle
What nerve provides sensory innervation of the larynx below the VC?

RLN
Thyroid or parathyroid surgery has the potential to cause damage to what nerve?

RLN
Unilateral RLN injury
- cord on the injured side will assume a paramedian position
- hoarse and weak voice
- increased risk of aspiration
What occurs with bilateral ischemia of the RLN?

Laryngospasm causing complete airway obstruction
What causes laryngospasm?
What nerve is involved
- Spasm of glottic muscles
- superior LN
The VC are at the level of the?

laryngeal prominence
cricoid cartilage is at the level of the ___ vertebra

C6
Why is the cricoid cartilage an important landmark?
- -site where carotid artery can be compressed against the transverse process of C6
- -junction of larynx and trachea
- -site where pharynx and esophagus join
- -point where RLN enters larynx
- -narrowest part of the pedi airway
3 parts of the pharynx
- nasopharynx- posterior to nose and superior to soft palate
- oropharynx- posterior to mouth
- laryngopharynx- posterior to larynx
T or F, the pharynx extends from the base of the skull to below the level of the body of C6 where it becomes continuous with the esophagus

T
Anesthesia goals r/t microlaryngoscopy
- Atraumatic intubation (minimize bleeding for surgical visualization)
- Protect tracheal with cuffed ETT
- Adequate oxygenation and ventilation (surgeon wants smallest ETT possible- as small as 4.5 mm)
- Minimize secretions- glyco often requested, minimize coughing in response to secretions
- Prompt wake up with return of protective reflexes
T or F, MR is typically NOT required for microlaryngoscopy

F
Why is microlaryngoscopy associated with 1.5-4% incidence of Mi or ischemia?
- suspended laryngoscope is stimulating
- can cause HTN, tachycardia, arrythmias
Possible techniques used to perform microlaryngoscopy
- apneic- alternate mask ventilation with surgical incision, use TIVA
- spontaneous breathing with deep anesthesia (tricky)
- jet ventilation
How does jet ventilation work?
- Utilizes the Venturi effect, Bernouli's theory
- VC must be relaxed
- Jet gas must be allowed to exit freely
- Use 100% O2, but air is entrained, so actual FiO2 < 100%
Contraindications / risks of jet ventilation
- pedi, obesity, emphysematous bullae
- risk= barotrauma
Laser

light amplification by simulated emission of radiation
CO2 laser
- most commonly used laser
- suitable for removing lesions on VC and larynx
- produces radiation with a wavelength of 0.01 mm
YAG and ARGON laser
- deep and penetrating effects
- suitable for detached retinas
- shorter wl than CO2 laser
Major anesthesia considerations r/t laser use

airway fire and eye protection (for all in room!!)
Strategies to avoid an airway fire
- fill cuff with NS or methylene blue
- avoid N20 (combustable)
- FiO2 <= 30%
Steps to take if an airway fire does occur
- First step = D/C O2
- Remove ETT
- re-intubate trachea
- flush pharynx with cold NS
- rigid broch to check for damage and presence of foreign bodies
- possibly steroids, humidified gas, abx
T or F, the nasal mucosa has minimal blood supply

F, rich blood supply
considerations r/t pts undergoing nasal or sinus surgeries
- pre-op nasal obstruction
- nasal polyps are associated with asthma and CF
max dose of cocaine

3 mg / kg
SE of cocaine
- HTN and ectopic ventricular activity
- cocaine inhibits reuptake of NE
Why are the eyes not taped for FESS?

Surgeon may want to periodically check for eye movement during dissection due to close proximity of the sinuses and the orbit
Is TIVA or volatile anesthesia preferred for nasal / sinus surgeries?

TIVA, propofol and remi are associated with less bleeding, better visualization, less coughing on emergence, decreased PONV
Why is MR preferred for FESS

movement could cause neuro or opthalmic damage
Major complications associated with FESS
incidence
- diplopia, CSF leak, CNS infection, stroke, carotid injury, death, orbital hematoma
- 1%
Causes of major complications

perforation of roof of ethmoid sinus, injury to optic nerve or carotid artery during a sphnenoidecotmy
Minor complications associated with FESS
incidence
- peri-orbital emphysema
- ecchymosis
- lip pain or numbness
- bronchospasm
- epistaxsis
- 5%
use of N20 for ear surgeries
- not recommended
- remember N20 is 34 x more soluble in blood than nitrogen
- N20 will enter air cavities faster than nitrogen can leave
- result is an increase in pressure
- also risk of otitis, disarticulating of the stapes, impaired hearing
- can also lead to PONV
how long should N20 be avoided for pts s/p reconstructive ear surgeries?

6 weeks
T or F, ear surgery alone is associated with increased PONV

T
T or F, PONV is not harmful to middle ear reconstruction?

F, it can undo it
facial nerve and otologic surgeries
- up to 3% incidence of facial nerve paralysis
- intra-op monitoring is usually performed so avoid MR
thyroid isthmus

bridge connecting the L and R lobes of the thyroid gland
Thyroid gland innervation

ANS
Thyroidectomy anesthetic considerations
- euthryoid status
- airway!!
How can you tell if a pt is euthyroid
- TFT
- resting HR < 85
- will decrease risk of thyroid storm by > 90%
Why are pts undergoing thyroidectomy at increased risk for airway issues?
- potential for a large goiter, causing:
- tracheal deviation
- tracheal ring involvement
- inflammation due to thyroiditis
MEN
- medullary thyroid cancer is associated with MEN (multiple endocrine neoplasia)
- this pt could have an diagnosed pheo
- catecholamine release could mimic thyroid storm and vice versa
- find out what the pre-op diagnosis is!!
What med is often used pre-op to render a pt euthyroid prior to thyroidectomy

lugol's solution
Your pt shows up for a thyroidectomy and admits to not taking their lugol's solution for last week, what should you do?

Elective surgery should be cancelled
Pt position for thyroid surgery

beach chair
Complications of thyroid surgery
- recurrent or superior LN paralysis
- -damage to RLN can lead to VC paralysis or airway obstruction
What actions are taken to prevent nerve damage during thyroidectomy?
- Nerve monitoring with a NIM ETT
- NDMR are avoided
What muscles are monitoring with EMG during thyroidectomy?

thyroarytenoid muscles (principle relaxers of the VC)
T or F, pts undergoing thyroidectomy are not at increased risk for eye injury

F, increased risk, possible exopthalmus
Why are hyperthyroid pts at increased risk for hepatic injury

accelerated biotransformation leading to increased metabolites
Use of NMB and thyroidectomy
- Typically avoided due to use of nerve monitoring
- If needed to use, use cautiously due to increased incidence of MG and myopathies in pts with thyrotoxicosis
T or F, hyperthyroidism itself increases the MAC and anesthetic requirements

F
T or F, a pt presenting with bleeding tonsils requiring re-operation does not require RSI

F, potentially swallowing blood and are thus considered full stomach
Anesthetic management for a bleeding tonsil
- T+C
- adequate venous access
- adequate volume replacement (blood loss under estimated thus pt is more hypovolemic than thought)
- no premedication as we want airway reflexes intact
Anesthesia risks associated with a peritonsillar abscess
- resp obstruction
- GA can cause further obstruction, careful intubation to avoid disrupting the abscess
- ? awake intubation
- ? elective trach
- difficult intubation as a result of trismus
- distorted anatomy
Epiglottitis

supraglottic obstruction 2/2 infection
Epiglottitis s/sx
- sore throat
- dysphagia
- muffled voice
- resp distress
Diagnosis of epiglottitis
- DL
- lateral neck x-ray may show characteristic thumb like epiglottic shadow
Why is trach set-up and ENT surgeon presence required for epiglottitis surgery?

Possibility of complete airway obstruction can occur at any time
Induction for epiglottitis
- Careful inhalation induction
- Avoid manipulation of the airway prior to induction
- Pt breathing spontaneously but deep
S/sx FBO
- sudden obstruction to breathing
- croupy cough
- wheezing
- hoarseness
Anesthesia management of FBO
- don't turn partial obstruction into complete obstruction
- must be ready to perform trach or cricothyroidectomy
- gentle mask induction without PPV or cricoid pressure is preferred
Why is close observation required after removal of a FB?

Laryngeal and subglottic edema can occur up to 24 hours after FB is removed
Superior laryngeal nerve block
- will anesthetize all laryngeal mucous membranes above the larynx?
- use cautiously in full stomach pts as it may remove some protective reflexes
glossopharyngeal nerve block
- 9th CN
- innervates posterior tongue, oropharynx, tonsils, gag reflex
- block can cause paralysis of the pharyngeal muscles
- tongue relaxation will cause some airway obstruction
if both a superior laryngeal and glossopharyngeal nerve block are performed, which should be performed first to avoid airway obstruction?

perform SLN block first
is glossopharyngeal nerve block alone sufficient for awake intubation?

no
max dose cocaine for LA?

3 mg / kg
max dose lido for LA?

3.5 mg /kg?
max dose tetracaine for LA?

??
radical neck dissection
- deep cervical lymph node and the tissues around them are removed as much as possible
- major arteries, brachial plexus, 10th CN and phrenic nerve are preserved
Use of NDMR for neck dissection

contraindicated b/c surgeon needs to identify the nerves
Lefort osteotomy purpose
- correct dental malocclusion
- correct congential abn
- correct maxillary deformities
lefort 1 fracture
- simple horizontal fx of the lower maxilla just above the teeth and the palate
- maxilla is separated from the palate
lefort 2 fracture
- crosses the nasal bones on the ascending processes of the maxilla
- crosses the medial and inferior orbital rims
- separates maxilla from the face
lefort 3 fracture
- high level transverse fx
- crosses front of maxilla and the lacrimal bone and goes thru the orbits
Dural tears occur 25% of the time in Lefort __ and __ fxs

2 and 3
In what pts should nasal intubation be avoided?
- Lefort 2 or 3 fx
- nasal, orbital, or zygomatic fx
why is it especially important to give anti-emetics with a lefort osteotomy procedure?
- jaw is wired shut at end
- want to prevent PONV!
T or F, the eye can easily accommodate increases in volume?

F, pressure will increase with an increase in volume due to rigid wall
Normal IOP

12-20 mmHg
What factors can influence IOP
- movement of aqueous humor
- changes in blood volume
- CVP
- extraocular muscle tone
- arterial BP and ventilation
T or F, succ increases IOP more than intubation

F, intubation increases IOP more than succ alone
what effect does an increase in the following have on IOP?
- CVP- incr
- ABP- incr
- PaCO2 (hypovent)- incr
- hypoxia- incr
What effect do volatiles, N20, barbs, and benzos have on IOP?

Increased IOP
What effect does succ have on IOP?

Increases IOP by 5-10 mmHg for 5-10 minutes after administration
What effect does diamox have on IOP?
- Diamox is a carbonic anhydrase inhibitor
- decreases IOP
T or F, 2/3 of aqueous humor is an active secretory product of the carbonic anhydrase enzyme system?

T
Aqueous humor flow is r/t to what equation?

Poiseuille's Law
Respiratory _____, hy___thermia, and hypoxia will increase IOP.
- acidosisi
- hypoxia
- hyperthermia
Echothiapate is a _____ ____ and will ____ the effect of succ.
- cholinesterase inhibitor
- prolong
Most common pedi eye surgery in the US

strabismus repair
Common SE of strabismus repair

oculocardiac reflex (bradycardia) and oculogastric reflex (vomiting)
Examples of open eye surgeries
- Cataract extraction
- corneal laceration repair
- corneal transplant
- removal of FB
- ruptured globe repair
- secondary intraocular lens implantation
- vitrectomy (ant and post)
- wound leak repair
- peripheral iridectomy
Eye sensation

afferent fibers from cornea and conjunctiva to 1st branch of 5th CN= trigeminal nerve
Motor innervation of the extra-occular muscles
- Motor fibers of the 3rd CN (oculomotor) to all eye muscles expect lateral rectus
- Lateral rectus is innervated by the 6th CN (abducens)
What type of block is typically done for cataract surgery?

Peribulbar block
What does blockade of the facial nerve with 1% lido do?

Sensory anesthesia of the periorbital area and motor lid block
Why is hydraluronidase added to retro-bulbar injections?

enzyme that promotes the spread of anesthetic thru the muscle column
What are the 3 goals of the retrobulbar block?
- anesthesia
- akinesia
- abolishment of OCR
What's the difference btw retro and peri bulbar blocks?
- retrobulbar block- needle enters intraorbital muscle cone (intraconal)
- peribulbar block- needle does not enter infraorbital muscle cone (extraconal)
Most frequent complication of retrobulbar blocks
- hemorrhage
- 1% of cases
S/sx of hemorrhage from a retrobulbar block
- immediate downward displacement of the eyeball
- appearance of subconjunctival blood
- serious complication that can interfere with retinal blood supply if excessive pressure develops
- surgery is cancelled and drainage may be performed by the surgeon
Brainstem anesthesia
- SE of a retrobulbar block
- LA spreads along optic nerve to central brainstem
- pt becomes apneic
- tx= ventilation and supportive tx until s/sx resolve
- s/sx= SOB, dysphasia
IM injection
- SE of retrobulbar block
- want to inject into cone, not directly into muscle
- stop injecting if there is any rx!!
Oculocardiac reflex
-what CN are involved
-which is afferent (sensory) and which is efferent
- AKA five and dime reflex (CN 5 and 10)
- afferent- CN 5 trigeminal
- efferent- CN 10 vagal
Causes of OCR
- pressure on eye
- traction of extra ocular muscles
- orbital hematoma
- ocular trauma
- eye pain
Most common surgery to see OCR

strabismus surgery in children
S/sx OCR
- bradycardia, nodal rhythm, ectopy, asystole
- somnulence
- nausea
OCR treatment
- d/c stimulus (surgeon usually)
- give anti-muscarinic
T or F, the OCR will eventually fatigue itself with repeated traction on the extra ocular muscles

T
How does PaCO2 level affect incidence of bradycardia during strabismus surgery?
- Hypoventilation and increased PaCO2 will increase the incidence of bradycardia
- maintain normocarbia
Disadvantage of peribulbar block over retrobulbar block
- slower onset (placed further from optic and other nerves)
- need for reinjection more often

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ariadne9

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ENT Anesthesia

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ENT

Updated

2014-04-12T14:52:00Z

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