ENT Part I

Question 1

How many muscles of the eye are there?

Answer 1

6

Question 2

These muscles are innervated by the oculomotor nerve

Answer 2

Oculomotor nerve = CN III

• Superior rectus
• medial rectus
• inferior rectus
• inferior oblique.

Question 3

This muscle is innervated by the abducens nerve

Answer 3

abducens nerve = CN VI

• Lateral rectus (LR6)
• Moves the eye down and outward.

Question 4

This muscle is innervated by the trochlear nerve

Answer 4

trochlear nerve = CN IV

• Superior oblique (SO4)
• moves the eye down and out

Question 5

Functions of the oculomotor nerve.

Answer 5

1. Innervates 4 of the eye muscles
   
   1. superior rectus
   2. medial rectus
   3. inferior rectus
   4. inferior oblique
2. Also causes pupillary constriction and eyelid opening.

Question 6

Innervation of the trigeminal nerve

Answer 6

3 branches total, but two SENSORY branches for the eye

1. Ophthalmic branch
   
   • Innervates upper eyelid, conjunctiva, and cornea
   • Nasociliary branch of the ophthalmic nerve
     
     • sensory to the medial canthus, lacrimal sac, and ciliary gangion (cornea, iris, and ciliary body)
   • Also reulates oculocardiac reflex
2. Maxillary branch - Sensory to lower lid

Question 7

Topical anesthesia eye drops do a great job at blocking this, but not this

Answer 7

• Good for blocking the trigeminal nerve, which innervates the cornea.
• Bad at blocking the eyelids = Need extra anesthesia to relax the lids for traction.

Question 8

Injury to this nerve can result in total blindness

Answer 8

1. Optic nerve (CN II) which is part of the optic chiasm
   
   • nerve, artery, and sympathetic nerves

Question 9

Where is aqueous humor produced?

Answer 9

1. 2/3 is made in the posterior chamber by the ciliary body.
   
   • Once produced, it is actively moved from the posterior to the anterior chamber via an active sodium pump mechanism.
2. 1/3 is produced by passive filtration through vessels in the iris

Question 10

How fast is aqueous humor produced?

Answer 10

2uL/min

This is the same as 0.12mL per hour.

Sooooo not very fast!

Question 11

How is aqueous humor eliminated?

Answer 11

1. It drains out of the eye through a spongy tissue called the trabecular meshwork.
2. From the meshwork, it drains into Schlemm’s canal and the episcleral venous system located in the anterior chamber, eventually ending up at the SVC and RA.

Question 12

What is normal IOP and what factors determine it?

Answer 12

Normal IOP is 10-20mmHg

• 4 players in determining IOP:
  
  • Production of aqueous humor
  • Drainage of aqueous humor
  • Changes in the choroidal blood volume or pressure
  • EOM (extraocular muslce) tone

Question 13

The globe of the eye is a pretty non-compliant structure, the volume of the compartments is fixed, with these two exceptions

Answer 13

1. Aqueous fluid
2. Choroidal blood volume.

These volumes can change and regulate the IOP.

Question 14

These factors can increase IOP

Answer 14

Major problem if the globe of the eye is exposed (in eye trauma) because it will lead to spillage of contents of the eye. Gross!

1. Drugs:
   
   • Ketamine
   • Sux (up to 8mmHg increase in IOP d/t fasciculations.
2. Other:
   
   1. Position changes
   2. coughing
   3. valsalva maneuver
   4. straining, vomiting
   5. HTN
   6. injection of local anesthesia
   7. laryngoscopy
   8. hypercarbia
   9. lid pressure, eye compression, forceful eyelid squeeze

Question 15

These factors will decrease IOP

Answer 15

Drugs:

• Most anesthetic drugs
• NDMRs
• Hypertonic solutions (3%NS, mannitol, etc)

Other:

• Hypotension
• hypothermia
• hyperventilation (low CO2 –> similar to decreasing ICP!)

Question 16

Examples of topical ophthalmic drugs and their effects

Answer 16

1. Acetazolamide
   
   1. Used to tx glaucoma
   2. Induces diuresis
   3. May cause K+ depletion
   4. want preop labs
2. Ecothiophate
   
   1. Used to tx glaucoma
   2. Topical anticholinesterase
   3. maintains miosis
   4. May cause inhibition of plasma cholinesterase;
   5. caution with succinylcholine and toxicity with ester-type local anesthetics
3. Phenylephrine - Alpha agonist;
   
   1. causes mydriasis
   2. Associated with severe HTN
4. Acetylcholine - Cholinergic drugs
   
   1. constrict pupil
   2. Can cause bradycardia and acute bronchospasm
5. Timolol - Used in the tx glaucoma
   
   1. Topical beta blocker
   2. May cause bradycardia, bronchospasm, CHF
6. Ketorolac and Diclofenac
   
   1. Both are NSAIDs - Used for inflammation
7. Mitomycin C - Chemotherapeutic drug
8. Atropine = Pupil dilation
9. Cyclopentolate = Potent pupil dilation

Question 17

This glaucoma med must be stopped 4-6 weeks prior to surgery

Answer 17

Ecothiophate

• topical anticholinesterase
• inhibition of plasma cholinesterases d/t systemic absorption
  
  • sux (prolonged NMB)
  • ester-type LA toxicity (because the ESTERs and metabolized by plasma ESTERases)

Question 18

This chemo agent is used ophthalmically to promote smooth healing of the eye

Answer 18

Mitomycin C.

• prevents excessive cellular proliferation results in scarring.

Question 19

Nerves that mediate the oculocardiac reflex (OCR)

Answer 19

1. Trigeminal (afferent)
2. Vagal (efferent)

Question 20

S/S of the OCR

Answer 20

1. Bradycardia
2. AV block
3. ventricular ectopy
4. asystole

Question 21

What triggers the OCR?

Answer 21

1. Pressure on the globe
2. pain
3. traction on the EOMs
4. retrobulbar block
5. eye trauma
6. hypoventilation
   
   1. ( hypercarbia increases IOPs)

Question 22

OCR occur most often during this type of surgery****

Answer 22

Strabismus surgery

(due to manipulation of the EOMs) This was italicized on the ppt. Possible test question.

Question 23

How can you try to prevent the OCR, and how do you treat the OCR if it happens?

Answer 23

Prevention:

• Maintain normal EtCO2
• Pretreat with anticholinergics like Glyco (this is not normally necessary)

Treatment:

• Tell surgeon to stop the stimulus. Let them know what is happening.
• Assess their ventilatory status (what is their EtCO2 looking like?) –> may want to hyperventilate
• Atropine if necessary in 7mcg/kg increments -
• Injection of LA into the EOMs

Question 24

What is a big thing you need to assess for before an eye surgery?

Answer 24

1. Is the patient able to cooperate and lie still?
   
   • If not, do a general anesthetic.
2. Conditions it is difficult to lie supine and lie still:
   
   • SOB, OSA, chronic cough, nasal drip, reflux, nausea, Parkinson’s, Alzheimer’s or claustrophobia, mentally disabled, back pain, pediatric patients

Question 25

What to tell you patient regarding before eye surgery?

Answer 25

1. continue their **home** **medication** regimen 2. Let them know they need to **lie** **still** and may be **awake** for the procedure. 3. Avoid **overhydration** --\> awake and may have to pee

Question 26

**Goals** of anesthesia for eye surgery

Answer 26

1. Safety (ability to manage airway with limited access), 2. control HTN 3. avoid overhydration 4. akinesia 5. analgesia 6. taking steps to avoid the OCR 7. preventing increase in IOP 8. **smooth emergence** (avoiding retching, vomiting, coughing etc than can increase IOP and rupture stitches) 9. awareness of drug interactions (ecothiophate and sux/ester-LAs)

Question 27

**Advantage of regional** over general anesthesia **for eye surgeries**

Answer 27

1. Provides good analgesia 2. Less occurance of N/V 3. Faster recovery and discharge 4. Cheaper

Question 28

Anesthesia/sedation for **retrobulbar** **block**

Answer 28

* Usually, patient **sedated for the block** and then wake them back up. * They are **supine** with **HOB up 10-15 degrees**. Nasal cannula in place with ASA monitors. * **Propofol** can be given in small increments (20mg). * no analgesia = patient may startle on **needle** **insertion**. * **Remifentanyl** is another option (.3-.5mcg/kg). * Lasts **2-5 minutes**, long enough for placement of the block. * Can give **midazolam** in addition to these two meds depending on the pt's age. * Infusions are not necessary because **we want the patient to be aware an unobtunded during the procedure.**

Question 29

**Local anesthesia** for retrobulbar block

Answer 29

* LA deposited **posterior to the eye** in the **orbital** **cone**. * **2% lido** with **0.75% bupivicaine** in a **1:1 ratio**. * **2-3cc** total are deposited. * **Hyaluronidase** can be added for tissue penetration. * This block provides excellent akinesia and analgesia. * "**Conan's Cup**" puts pressure on eye to spread the local

Question 30

**Complications** of retrobulbar block

Answer 30

1. **Retrobulbar hemorrhage** most common\* 2. Globe perforation 3. OCR 4. Seizures (d/t subarachnoid injection) 5. Resp arrest 6. Optic nerve dammage

Question 31

Peribulbar block

Answer 31

1. **Safer** than retrobulbar → it is not injected within the cone. 2. Requires **higher volumes of LA**. 3. Onset is **slower**. 4. **Lower** incidence of eye **akinesia** 5. Most common complications * **globe** **perforation** * **block** **failure** → may not hit the top part of the eye (lower parts and muscles will be anesthetized, but top will not)

Question 32

Subtendon blockade

Answer 32

1. LA is injected under the Tenon's fascia 2. Excellent analgesia for the **iris** and **anterior** **eye** 3. Can cause **conjunctival edema** 1. **​**This is not common anymore because topicals work so well.

Question 33

Facial nerve block

Answer 33

1. Gives anesthesia to the **eyelids**. 2. Not very common. 3. **2-3cc** of LA is given where the **facial nerve exits** the chondyle of the mandible. 4. Complications include: 1. facial droop 2. vocal cord paralysis 3. respiratory distress ## Footnote Let the patient know that they will have facial droop after the procedure\*\*

Question 34

**Topical anesthetics** for eye surgery

Answer 34

1. **Proparacaine**, **tetracaine**, and **lidocaine** are commonly used 2. Provides anesthesia to the **cornea** and **conjunctiva** **ONLY**\*\* * Need to provide **extra sedation** so the pt is still/cooperative. 3. Disadvantage of this is that the **eye can still move** * no akinesia * pt may have increased anxiety and discomfort

Question 35

**Sedation** for eye surgeries

Answer 35

1. Have the pt position themselves comfortably 2. ASA monitors and nasal cannula 3. **Propofol** bolus of **0.5mg/kg** for block placement only 4. **Midazolam** **0.5-1mg** and/or **fentanyl** **12.5-50mcg** 5. Avoid build-up of CO2 under the drapes. * May need suction under the drapes.

Question 36

General anesthesia **goals** during eye surgery induction maintinence emergence post-op

Answer 36

**Induction** 1. Smooth intubation * avoid SNS response which can increase IOP). * blunt responses to airway maneuvers. 2. Avoid ketamine and sux (can increase IOP) - 3. Avoid N2O 4. LMA is ok **Maintenance** 1. AVOID hypoventilation (will increase EtCO2 and IOP) - 2. Treat HTN promptly 3. Avoid bucking and patient movement **Emergence** 1. Prevent coughing, bucking, and vomiting 2. Pre-treat with antiemetics 3. Ask the surgeon how much coughing patient can tolerate. 1. For some procedures, it is more important to prevent coughing/bucking than others. **Post-op** - Treat pain and PONV

Question 37

What is **open-angle glaucoma**, and how is it **treated**?

Answer 37

1. Slow development caused by sclerosis of the trabecular meshwork 1. resulting in blockage of drainage of the aqueous humor. 2. Treatment 1. miosis (pupillary constriction) 2. decreasing production of aqueous hummor 3. stretching of the trabecular meshwork

Question 38

What is **closed-angle glaucoma**, and how is it **treated**?

Answer 38

1. This is an **acute** **process** where the peripheral aspect of the iris bulges forward and **prevent drainage of the aqueous humor**. 2. Treatment involves **immediate surgery.**

Question 39

Anesthesia **goals for glaucoma surgery**

Answer 39

1. Continue medical management to **maintain miosis** 2. Limit the use of **anticholinergics** like **glyco** and **atropine** (cause dilation) 3. **AVOID** **increases in IOP** 4. Severe attack = **Mannitol** or **Acetazolamide** (Diamox)

Question 40

What is the leading cause of **treatable blindness**?

Answer 40

Glaucoma

Question 41

**Usual** **anesthesia** given for **glaucoma** surgery

Answer 41

**Regional** or **topical** block with **sedation**

Question 42

Surgical treatments for **retinal detachment**

Answer 42

1. Scleral buckle 2. vitrectomy 3. pneumatic retinopexy 4. cryotherapy

Question 43

These gases can be used for **intravitreal injection of gases** to treat **retinal detachment**

Answer 43

1. **Sulfur hexafluoride** (SF3) * No N2O for **10 days** post-injection 2. **Perfluoropropane** (C3F8) 1. No N2O for **30 days** post-injection 3. If patient has had surgery for retinal detachment, it's important to know when that was, and what gas was used if within the last month. But no one uses nitrous anymore anyway, so who the fuck cares.

Question 44

Anesthesia **considerations** for **open globe eye injury**

Answer 44

1. Pt is probably a **full stomach.** 2. **RSI should be performed**, but we don't want increased IOP, so no **ketamine** or **sux**. 1. Probs use **high dose Roc**. 2. If sux necessary, give defasciculating dose of roc 3. **Eye** **blocks** are usually **contraindicated** in open globe injury.

Question 45

Considerations for **strabismus** surgery

Answer 45

1. Strabismus is often due to **myopathy** of the **EOMs** 2. Common surgery for **pediatrics** 3. High incidence of **PONV** 4. Risk for **MH** 5. Highest risk for **OCR** d/t muscle manipulation

Question 46

The superior laryngeal nerve innervates this muscle. Damage causes this.

Answer 46

Cricothyroid muscle. * This muscle normally elongates and tenses the cords. * Thus, unilateral damage causes a **weak, lower pitched voice**, and puts the patient at risk for aspiration.

Question 47

This nerve inneravtes all **intrinsic muscles muscles of the larynx, except the cricothyroid muscle.** Damage results in this.

Answer 47

**Recurrent laryngeal nerve.** 1. Unilateral injury causes a **paralyzed VC** and **vocal hoarseness**. 2. **Bilateral** injury results in **respiratory** **distress**.

Question 48

Treatment of **corneal abrasion.**

Answer 48

Give **antibiotic** **ointment** and **cover** the **eye**.

Question 49

**Chemical** **injury** to the eye is often from

Answer 49

**Betadyne** or **chlorprep** getting in the eye.

Question 50

What is the **principal concern** for **ALL ENT** surgeries??

Answer 50

Providing a **clear, free,** and **unobstructed airway**\*\*\*

Question 51

General Principles of **ENT** Surgery

Answer 51

SIMPLE 1. Provide **complete** **control** **of airway** with no risk of aspiration 2. Control ventilation with adequate **oxygenation** and **CO2** **removal** 3. Provide **smooth** induction and maintenance of anesthesia 4. Provide a **clear, motionless** surgical field, free of secretions 5. Not impose time restrictions on the surgeon 6. Not be associated with any risk of **airway** **fire** or **CV instability** 7. Allow **safe emergence** with no coughing, bucking, breath holding, laryngospasm 8. Produce a **pain-free, comfortable, alert patient** at the end

Question 52

Pre-op assessment and planning for airway surgery

Answer 52

Pre-Op Assessment * NEED EXCELLENT **AIRWAY ASSESSMENT** * Size, mobility, location of any airway lesions * If stridor is present, it implies an airway diameter of pharynx reduved

Question 53

Considerations for **maintenance** of airway surgery

Answer 53

1. **Anticholinergics** -- reduce vagal tone, secretions, and cause bronchodilation 2. **Corticosteroids** -- Decrease edema, reduce PONV, and prolong the effects of LAs 3. **PONV** -- give antiemetics * pt may have **blood in the stomach** causing N/V * **throat packing** may be in place 4. Surgeon may want **controlled hypotension** * A-line -- Nitroglycerin, nitroprusside, etc.

Question 54

**Post-op** considerations for airway surgery

Answer 54

1. Observe for **edema** and **bleeding** * **​Steroids** and **racemic epi** can help control laryngeal edema * **Head up** to decrease edema 2. Give **humidified O2** 3. Watch for **pneumothorax** and **resp failure**

Question 55

Is **jet ventilation** considered an open or closed system?

Answer 55

Open. 1. Remember there MUST be a way for the air to be exhaled passively. * Because you must have an **exit**, you also have an **entrance** for air to be entrained into the system with each burst from the **jet ventilator d/t the venturi effect**

Question 56

Advantages and disadvantages of a **closed system with a cuffed ETT**

Answer 56

**Advantages**: * Routine technique * Protection of lower airway * Control of airway * Control of ventilation * Minimal pollution by volatile anesthetics **Disadvantages**: * Surgical access and visibility limited * High inflation pressures needed with small ETT tubes * Vocal cord damage with intubation * Risk of laser airway fire

Question 57

These are the **only types of cuffs** that are **resistant to lasers**

Answer 57

Cuffs wrapped in **metal foil** (usually aluminum or copper). * Also, cuff will be filled with **methyline blue**. * This helps **detect cuff rupture** and the liquid helps **prevent airway fire**.

Question 58

Examples of **open systems**

Answer 58

Natural airway with insufflation Jet ventilation

Question 59

Technique of **spontaneous ventilation with insufflation of anesthetic gases**

Answer 59

Patient has natural airway, and anesthetic gases are insufflated via one of these mechanisms: 1. **Nasal trumpet** 2. A **small catheter in nasopharynx** that terminates just above the laryngeal opening 3. A **ETT tube** that is cut short and placed in nasopharynx, extending just beyond the soft palate 4. Gases can also be insufflated via the **side-arm channel** of a laryngoscope or bronchoscope

Question 60

What are some of the vessels through which jet ventilation can take place?

Answer 60

1. A **jetting needle** attached to a laryngoscope or bronchoscope 2. **Transtracheal cathete**r through the cricothyroid membrane 3. A **small-diameter cuffed ETT** specifically designed for jet ventilation

Question 61

Jet ventilation can provide respiratory rates as high as

Answer 61

1. **100-150** breaths per minute 2. Automated high-frequency ventilators have alarms that will automatically interrupt ventilation if pressure limits are reached

Question 62

Anesthetic technique with jet ventilation

Answer 62

1. Preoxygenation 2. IV induction 3. NDMR\*\*\* 4. Laryngoscopy 5. Topical local anesthesia 6. LMA or ETT inserted 7. Ventilation with 100% oxygen until surgeon ready to site the rigid laryngoscope with jetting needle 8. Anesthesia maintained with **propofol infusion + remifentanil infusion** 9. **At the end of surgery**: LMA reinserted, NDMR antagonized, Anesthetic infusions stopped, Smooth awakening and LMA/ ETT removal

Question 63

How can you continuously assess that your **jet ventilation is adequate?**

Answer 63

1. Observing chest movements 2. O2 sats 3. Listening for changes in sounds during air entrainment and exhalation 4. Observing airway patency

Question 64

Complications of jet ventilation

Answer 64

1. Crepitus 2. Pneumothorax 3. Gastric distention

Question 65

Why are **lasers** used in airway surgery?

Answer 65

Usually for their **thermal effects** to *cut, coagulate, and vaporize tissues.*

Question 66

What are some of the **advantages** of laser use in airway surgery?

Answer 66

1. Very precise 2. minimal edema 3. minimal bleeding.

Question 67

What are some of the **characteristics of the laser beams used?**

Answer 67

1. They have **one wavelength** 2. they move in the **same direction**, and its **beam is parallel**

Question 68

Why are **CO2 lasers** common in airway surgeries?

Answer 68

D/t **extreme precision** and **shallow depth of burn**

Question 69

What are some of the **hazards of laser** use in airway surgery?

Answer 69

1. AIRWAY FIRE!!!\*\* 2. Atmospheric contamination * Plume of smoke and fine particulates * Deposition in lungs * Leads to pneumonia, inflammation, viral infections 3. Perforation of a vessel or structure 4. Embolism 5. Inappropriate energy transfer 1. Reflection and **scatter of beams** can cause immediate or delayed injury to normal tissue, especially the eyes 6. CO2-reacts at surface causing corneal damage 7. Nd: YAG/argon-pass thru the cornea to the retina 1. TAPE PT EYES CLOSED AND COVER WITH WET GAUZE 2. Pt may need special goggles as well -- PROTECT YOUR OWN EYES

Question 70

Risks for **airway fire** and damage it can cause

Answer 70

Risks/damage 1. Lasers cause **intense heat** that can ignite a **fire** * **CO2** lasers can **penetrate an ETT** and ignite a fire. * **N2O** supports fires!!!! 2. Damage is usually caused to the **subglottic, epiglottic**, and **oropharyngeal** structures 3. **Smoke inhalation** can result in **bronchospasm** and **chemical injury** that can lead to respiratory failure

Question 71

Strategies to **reduce the incidence of airway fires**

Answer 71

1. Reduce the flammability of the **ETT** * metal wrapping, fluid filled cuff, etc 2. Remove flammable **materials** from the airway * ex-- making do without an ETT by using **jet** **ventilation** or **intermittent** **extubation**. * Pt may experience periods of **apnea**. 3. Use **lowest tolerated O2 concentrations**

Question 72

**Treatment** of airway fires

Answer 72

1. **Remove** burning ETT and/or other material from airway 2. **Stop** ventilation D/C oxygen 3. **Flush** the pharynx with cold saline 4. **Mask** with 100% O2 5. Laryngoscopy and bronchoscopy to **assess damage** 6. Administer **humidified gas, steroids, antibiotic** 7. May need to **reintubate**, or even **trach**, and control ventilation 8. Check ABGs, SpO2, CXray, etc