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Mar: Sem 6 - Principles B > Anesthesia for Eyes > Flashcards

Anesthesia for Eyes Flashcards

1
Q

What is the outermost layer of the eye called?

A

Sclera

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2
Q

What surgery is the most common in the elderly?

A

Eye Surgery

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3
Q

What is the anterior-most portion of the eye called?

A

Cornea

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4
Q

What is the middle layer of the eye called?

A

Uveal Tract

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5
Q

What are the layers of the Uveal Tract?

A
  • Choroid
  • Iris
  • Ciliary Body
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6
Q

What is the function of the Choroid?

A

A layer of blood vessels located posteriorly that provides blood flow to the eye

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7
Q

What can bleeding in the Choroid lead too?

A

Intraoperative Explusive Hemorhage

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8
Q

Where do sympathetic fibers of the iris originate from?

A

Carotid Plexus

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9
Q

Where do parasympathetic fibers of the iris originate from?

A

Oculomotor Nerve

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10
Q

The sympathetic fibers of the iris travel through the ciliary ganglion to innervate this muscle.

What does this muscle do when contracted?

A
  • Dilator Muscle
  • Contraction of Dilator Muscle dilates the pupil
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11
Q

The parasympathetic fibers synapse in the ciliary ganglion to innervate this muscle.

What does this muscle do when contracted?

A
  • Iris Sphincter Muscle
  • Contraction of iris sphincter causes pupillary constriction.
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12
Q

What does the ciliary body of the eye produce?

A

Aqueous Humor

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13
Q

What is the center of the eye filled with?

A

Vitreous Gel

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14
Q

How many extraocular muscles are there?

A

6 extraocular muscles

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15
Q

The ophthalmic artery is branched from where?

A

Branch from the internal carotid artery

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16
Q

What supplies the majority of blood to orbital structures?

A

Ophthalmic artery

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17
Q

The ophthalmic vein drains blood directly into a _________.

A

cavernous sinus

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18
Q

Which CN transmits neural signals from the retina?

A

Optic Nerve (CN II)

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19
Q

Which CN controls extraocular muscle movement?

A
  • Oculomotor Nerve (CN III)
  • Trochlear Nerve (CN IV)
  • Abducens Nerve (CN VI)
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20
Q

Which CN is responsible for touch and pain sensation?

A
  • Trigeminal Nerve (CN V)
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21
Q

Which CN is responsible for motor innervation to orbicularis muscle via zygomatic branch?

A
  • Facial Nerve (VII)
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22
Q

A blockade on CN VII will prevent this from “squeezing”.

A

Eyelid

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23
Q

Which nerve provides sensation to the upper eyelid

A

Frontal branch of ophthalmic nerve

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24
Q

Which nerve provides sensation to the lower eyelid

A

Maxillary nerve

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25
Q

What is normal intraocular pressure (IOP)?

A

10-20 mmHg

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26
Q

At what pressure is IOP considered pathological and will need treatment?

A

Greater than 25 mmHg

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27
Q

In anesthesia, what factors can increase intraocular pressure?

What two factors cause the most significant increase in IOP?

A
  • Direct Laryngoscopy and Emergence
  • Changes in intraocular content
  • External pressure (masking)
  • Patient Positioning (prone)
  • Coughing, straining, vomiting
  • Hypercapnia
  • Hypoxia
  • Hypertension
  • Drugs (Sux, Ketamine, Neostigmine/Atropine, etc)
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28
Q

Intraocular perfusion pressure formula

A

MAP - IOP

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29
Q

Blood supply to the retina and optic nerve depends on ______________ Pressure

A

Blood supply to the retina and optic nerve depends on Intraocular Perfusion Pressure

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30
Q

What is believed to cause the chronic pressure elevation in open-angle glaucoma?

A

Sclerosis of the trabecular mesh network

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31
Q

___________ is primarily regulated by the resistance at the trabecular meshwork

A

Intraocular Pressure

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32
Q

What fluids in the eye help regulate IOP

A
  • Quantity of Aqueous Fluid
  • Choroidal Blood Volume
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33
Q

How much increase in IOP would be caused by coughing, straining, and vomiting?

A

30-40 mmHg

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34
Q

How does hypercapnia increase IOP?

A

Hypercapnia causes choroidal congestion, which causes an increase in IOP.

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35
Q

Intravenous succinylcholine causes IOP to increase by ________ mmHg (range)

A

8-10 mmHg

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36
Q

How does succinylcholine increase IOP?

A
  • Reduced aqueous humor outflow
  • Increased choroidal blood volume
  • Increased central venous pressure
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37
Q

How long does the increased IOP last if succinylcholine is administered?

A

5-10 minutes

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38
Q

Intravenous ketamine causes IOP to increase by ________ mmHg (range)

What is the increase in IOP from ketamine related to?

A
  • 2-3 mmHg
  • Increase BP from the effects of ketamine
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39
Q

How does Sugammadex increase IOP?

A

Trick question.
Sugammadex does not increase IOP.

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40
Q

Ocular blocks increase IOP by ______ mmHg (range).

IOP will return to baseline within _____ mins.

A
  • 5-10 mmHg
  • 5 minutes
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41
Q

Which block will cause the greatest increase in IOP?

What is this due to?

A
  • Peribulbar Block
  • D/t large volume of LA that is injected
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42
Q

What patient position will increase IOP?

A
  • Supine
  • Prone
  • Trendelenburg
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43
Q

Normal blink increases IOP by ____ mmHg

A

10 mmHg

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44
Q

Forceful lid squeeze increases IOP by ________ mmHg

A

70 mmHg

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45
Q

In anesthesia, what factors can decrease intraocular pressure?

A
  • Volatile agents & IV anesthetics
  • Short-acting opioids
  • Mannitol
  • Acetazolamide
  • Echothiophate
  • Timolol
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46
Q

How does VA decrease IOP?

A

Depression of CNS ocular centers → relaxation of extraocular muscle tone

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47
Q

Volatile agents & IV anesthetics can cause a dose-dependent reduction of IOP by ________% (range)

A

30-40%

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48
Q

Mannitol causes a decrease in IOP lasting ______hours (range)

A

5-6 hours

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49
Q

Effects of Midazolam, Nitrous Oxide, and Nondepolarizing neuromuscular blocking agents (NMBA) on IOP.

A

No effect

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50
Q

What is another name for the oculocardiac reflex?

A

Trigeminovagal Reflex

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51
Q

What are the triggers for the oculocardiac reflex?

A
  • Traction on extraocular muscles (specifically the medial rectus muscle)
  • Pressure on globe
  • Retrobulbar block
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52
Q

The oculocardiac reflex may be accompanied by _______ in the awake patient.

A

Nausea

53
Q

The oculocardiac reflex is most commonly seen in children for this surgery.

A

Strabismus repair

54
Q

Clinical presentation of the oculocardiac reflex during surgery.

A
  • Bradycardia
  • AV block
  • Ventricular Ectopy
  • Asystole
55
Q

Give the pathophysiology of the oculocardiac reflex.

A
  • Afferent limb of the reflex limb arises from the ophthalmic division of the trigeminal nerve and travels to the Gasserian ganglion and the sensory nucleus of the trigeminal nerve near the fourth ventricle where it synapses with the motor nucleus of the vagus nerve
  • Efferent limb is via the vagus nerve to the heart → decreases in HR and contractility
56
Q

Oculocardiac Reflex Managment

A
  • IV pretreatment with atropine / glycopyrrolate before surgery begins
  • STOP surgery
  • Assess ventilation (worsened by hypercapnia/hypoxia)
  • Surgeon will infiltrate retus muscle w/ LA
57
Q

How will the oculocardiac reflex fatigue itself?

A

Repeated stimulation will decrease the reflex response

58
Q

Atropine dose for intraoperative oculocardiac reflex

A
  • 7-10 mcg/kg IV incrementally
  • Faster onset than glycopyrrolate
59
Q

Glycopyrrolate dose for intraoperative oculocardiac reflex

A

0.2 mg IV incrementally

60
Q

What is another name for Open Angle Glaucoma

A

Chronic Glaucoma

61
Q

How is Open Angle Glaucoma characterized?

A

Optic neuropathy characterized by progressive peripheral visual field loss followed by central field loss in a typical pattern

62
Q

How does Open Angle Glaucoma cause visual loss?

A
  • Trabecular meshwork sclerosis causes chronic pressure elevation
  • This process is usually gradual and painless
63
Q

Treatment for Open Angle Glaucoma

A
  • Lower IOP / decrease fluid production
  • Trabeculoplasty / trabeculectomy
64
Q

How is closed-angle glaucoma characterized?

A
  • Obstruction to aqueous drainage from closure of the anterior chamber angle
  • Caused by acute dilation of iris that blocks drainage
  • Rapid rise in IOP, PAINFUL
  • Blindness <24 hours if not treated
65
Q

Treatment for Closed Angle Glaucoma

A

Iridotomy

66
Q

Describe an iridotomy procedure to treat closed-angle glaucoma.

A

Laser peripheral iridotomy to create a small hole in the iris to allow fluid to flow more freely into the front chamber of the eye where it then can drain.

Pew Pew

67
Q

What medication and substances should patients avoid if they have closed-angle glaucoma.

A
  • DO NOT USE SCOPOLAMINE
  • Antihistamines & decongestants may cause increase in IOP d/t pupillary dilation
  • Antidepressants d/t anticholinergic effect – pupillary dilation & increased aqueous production
  • Benzodiazepines d/t relaxation of sphincter muscle of iris & mild anticholinergic effect
  • Coke, X, & MJ
  • Ipratropium bromide
68
Q

During strabismus repair for a 10 yo, the patient’s heart rate decreases from 89 bpm to 30 bpm. What is the cause?

A
  • Oculocardiac Reflex
  • This reflex is triggered by traction on the extraocular muscles, particularly the medial rectus muscle, or pressure on the globe.
69
Q

Name drugs that are used to treat glaucoma.

A
  • Acetazolamide (drainage)
  • Echothiophate (maintains miosis)
  • Timolol
  • Netarsudil
70
Q

MOA of Acetazolamide

A
  • Carbonic Anhydrase Inhibitor
  • It reduces the production of aqueous humor
71
Q

S/E of Acetazolamide

A
  • Alkaline diuresis → K+ depletion
  • PONV
72
Q

Systemic absorption of Acetazolamide is possible through ________ or __________

A
  • Conjunctiva
  • Nasal Mucosa
73
Q

MOA of Echothiophate

A
  • Anticholinesterase Inhibitor
  • Increased ACh → contraction of the ciliary muscle (miosis) → increase outflow of aqueous humor through the trabecular meshwork
74
Q

Anesthesia Considerations for Echothiophate

A
  • Systemic absorption → inhibition of plasma cholinesterase
  • Succinylcholine can cause prolonged paralysis
  • Inhibition of the metabolism of Ester-type LA → toxicity
  • Return of normal enzyme activity in 4-6 wks after d/c
75
Q

MOA of Timolol

A
  • Non-selective β blocker
  • Reduces the production of aqueous humor
76
Q

S/E of Timolol

A
  • Bradycardia
  • Bronchospasm
  • CHF exacerbation
77
Q

Timolol is contraindicated in what patient population?

A
  • Asthma
  • CHF
  • Conduction defects
78
Q

MOA of Netarsudil

A
  • Rho Kinase Inhibitor
  • ↓ IOP by increasing the outflow of aqueous humor through the trabecular meshwork
79
Q

Effects of Phenylephrine on the eyes

A

Pupillary Dilation

80
Q

Concentration of Phenylephrine eye drops

A

2.5%

  • Administration 10% phenylephrine contains 5 mg
  • 10% administration can result in hypertension, arrhythmias, and adverse cardiac
81
Q

What drugs cause pupillary constriction and are used for intraoperative lens extraction?

What are the S/E?

A
  • Pilocarpine/ Acetylcholine
  • Bradycardia, Bronchospasm
82
Q

What are cataracts?

A

The opacity of the crystalline lens of the eye

83
Q

A modern cataract surgery technique that uses ultrasonic energy to break up and remove a cataractous lens from the eye

A

Phacoemulsification

84
Q

Anesthesia for Cataract surgery

A
  • Topical or regional
  • Minimal IV medications
  • General is rare
85
Q

Cataract Anesthesia consideration

A
  • No supplemental O2 if femtosecond laser is being used to make the corneal incision, capsulotomy, and fragmenting the lens
  • Fire risk
86
Q

What is a corneal transplant called?

A

Keratoplasty

87
Q

What medication is used to maintain low and stable IOP during a corneal transplant?

A

Mannitol

88
Q

Anesthesia for Keratoplasty surgery

A
  • Complete eye akinesia required
  • Good analgesia postop
  • Prevent eye squeezing
  • No coughing / movement
  • Eye protection w/adequate perfusion
  • Prevent oculocardiac reflex
  • Usually a regional block is used
89
Q

Why is topical anesthesia not recommended for keratoplasty?

A

Poor option d/t duration & pain at end

90
Q

Criteria for GETA for a Keratoplasty?

A
  • Unable to lie flat
  • Restless w/tremor
  • Claustrophobic
  • Pediatrics
91
Q

What are the regional block options for a keratoplasty?

How much will IOP increase w/ each block?

A
  • Retrobulbar Block (4-6 mmHg)
  • Peribulbar Block (5-22 mmHg)
  • Sub-Tenon’s Block (no change in IOP)
92
Q

What are the advantages of using a regional block for a keratoplasty?

A
  • Intraop & postop analgesia
  • Akinesia
  • No oculocardiac reflex
  • Less PONV
  • Quicker recovery & discharge
93
Q

A 69-year-old male presents for a trabeculectomy. His medications include echothiophate eye drops. Which medication should be avoided in his anesthesia plan?

A
  • Any Ester-type LA may predispose a patient to local anesthetic toxicity (Procaine, Chloroprocaine, Tetracaine)
  • Don’t use Succinylcholine, prolonged muscle paralysis

Remember: Ester LA have only one “i”

94
Q

If medications fail to treat chronic glaucoma, what type of surgery may the patient be a candidate for to increase drainage of aqueous humor to reduce IOP?

A

Trabeculectomy

95
Q

What is used to decrease/ prevent flap scarring of a trabeculectomy?

A
  • Mitomycin-C
  • 5-FU
96
Q

What is Pytergium?

What is another name for it?

A
  • Triangular wedge of fibrovascular conjunctival tissue, r/t chronic sun exposure
  • Surfer’s eye
97
Q

What is used to prevent the recurrence of Ptyergium?

A

Mitomycin-C (MMC)

Ptyergium has a 30-80% recurrence rate – MMC is alkylated agent and inhibits DNA synthesis

98
Q

What type of anesthesia would be used for Ptyergium Excision?

A

Topical Anesthetic

99
Q

What term describes the lower eyelid turned outward d/t the effects of aging?

A

Ectropion

100
Q

What term describes the lower eyelid turned inward d/t the effects of aging?

A

Entropion

101
Q

What type of anesthesia would be used for Ectropion and Entropion Repair?

A

Local Anesthetic w/ Sedation

102
Q

Procedure that corrects defect, deformity, or disfiguration of eyelids. Removes redundant tissue of the eyelids

A

Blepharoplasty

  • Considered plastic surgery
  • Transconjunctival vs Skin approach
  • Local w/ sedation or GETA
103
Q

Dystrophy of this muscle will cause ptosis (droopy eye).

A

Levator Muscle

104
Q

What type of anesthesia would be used for Ptosis Repair?

A

Local Anesthetic w/ Sedation

105
Q

What term describes malalignment of the visual axis causing diplopia (double vision)?

A

Strabismus

106
Q

What is the most common eye surgery in children?

A

Strabismus Repair

107
Q

Children with strabismus will have what other underlying disorder?

A
  • Trisomy 21 (Downs)
  • Cerebral palsy
  • Hydrocephalus
  • Malignant hyperthermia
  • Myotonic dystrophy

May need to be cautious w/ Sux or VA for these patients

108
Q

What type of anesthesia would be used for Strabismus Repair?

Post-op Considerations for Strabismus Repair

A
  • General + Regional Anesthesia
  • No severe post-op pain
  • Severe PONV (50-80%)
  • Minimize opioids. Consider Ketorolac
109
Q

Anesthesia Considerations for Eye Trauma.

A
  • Considered full stomach
  • Sux vs. RSI Roc dose
  • GETA vs Regional
  • Decrease gastric volume/acidity (Bicitra)
  • Use Oral Rae Tube
  • Avoid hypercapnia, light sedation (↑ IOP)
110
Q

What advantages does regional anesthesia have over general anesthesia for eye procedures?

A
  • Significant postoperative analgesia
  • Nausea and vomiting are infrequent.
  • Return to ambulation faster
111
Q

What is often placed with the outlet on the chest to eliminate carbon dioxide and oxygen buildup under the drapes and to prevent claustrophobia?

A

Air Blower

112
Q

What makes up the local anesthetic used for regional eye blocks?

A

1:1 ratio of bupivacaine 0.75% and lidocaine 2% without epinephrine

113
Q

Why is Hyaluronidase added to local anesthetic for eye procedures?

A
  • Speed tissue penetration
  • Prevent anesthetic-related damage to the extraocular muscles
114
Q

How much Hyaluronidase is needed to facilitate permeability & quality of the block?

A

7.5 units/ mL of LA

115
Q

Name this block

A

Retrobulbar Block

116
Q

Name this block

A

Peribulbar Block

PERribulbar is PERfectly Straight
PERibulbar is also on the PERimeter of the Cone

117
Q

Describe the placement of a retrobulbar block

A
  • Behind globe of the eye
  • Inside the muscular cone
118
Q

The retrobulbar block will cause akinesia of the extraocular muscles. What CN will be involved?

A
  • II
  • III
  • VI
119
Q

The retrobulbar block will provide a sensory block for these structures.

A
  • Conjunctiva
  • Cornea
120
Q

Complications of a Retrobulbar Block. What is the most common?

A
  • Retrobulbar Hemorrhage (monitor for IOP elevation)
  • Hematoma
  • Optic nerve injury
  • Globe penetration
  • LAST (seizures, CNS excitation)
121
Q

With a retrobulbar block, this will be expected because the superior oblique muscle outside the muscle cone may not be blocked.

A

Some intorsion on downgaze

122
Q

Describe the placement of a peribulbar block

A

Inject above & below orbit

123
Q

The peribulbar block will cause akinesia to what CN?

A
  • III
  • VI

Incomplete akinesia, peribular block will not block CN II

124
Q

Pros of Peribulbar Block

A
  • Easier and Less painful to perform
  • ↓ Risk of Retrobulbar Hemorrhage
125
Q

Complications of Peribulbar Block

A
  • High spinal
  • Intraocular injection
126
Q

What topical anesthetic is typically used for the eyes?

A

0.5% Proparacaine

127
Q

Topical Anesthetic is limited to these structures of the eye.

A
  • Conjunctiva
  • Cornea
  • Anterior Sclera
128
Q

Topical Anesthetic do not block these eye structures.

A
  • Iris
  • Ciliary Body

Mar: Sem 6 - Principles B (14 decks)

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