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N931 Advanced Principles of Anesthesia I > Opthamology > Flashcards

Opthamology Flashcards

1
Q

vision loss

A
  • leading cause of blindness world wide is cataracts
  • DM leading cause of new cases of blindness among adults aged 20-74
  • other major causes = macular degeneration, glaucoma, and diabetic retinopathy
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2
Q

annulus of zinn

A

-annular ring of tissue around the optic nerve

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3
Q

orbits

A
  • two symmetrical bony enclosures in the front of the skull

- each contains an eyeball or globe and its associated structures

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4
Q

volume of each orbit

A

30 mL

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5
Q

opthalmic artery

A
  • first branch of internal carotid
  • passes into orbit through optic canal
  • lies inferolateral to optic nerve
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6
Q

visual axis

A
  • aka optic axis

- imaginary line from the midpoint of the cornea to the midpoint of the retina or macula

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7
Q

axial length

A
  • measurement of the visual axis

- measured preoperatively to determine appropriate intraocular lens

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8
Q

normal axial length

A

23-23.5 mm

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9
Q

hyperopia

A

farsighted

globe is less than 22 mm long

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10
Q

myopia

A

nearsighted
globe is greater than 24 mm
increased chance of puncturing globe
stretching of globe

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11
Q

globe

A
  • eyeball
  • suspended in the antero superior part of the orbit
  • contained within three layers
  • large posterior segment (vitreous humor, retina, macula, and root of optic nerve
  • small convex anterior segment (two chambers)
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12
Q

two chambers of the anterior segment

A
  • anterior chamber = immediately behind cornea, filled with aqueous humor produced by the ciliary body
  • posterior chamber = contains the lens
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13
Q

cranial nerves important for the eye

A

II, III, IV, V, VI, VII, X

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14
Q

optic nerve

A
  • CN II
  • orbital portion of the optic nerve is 25-30 mm long and travels posteriorly within the muscle cone
  • 4 mm diameter
  • not a TRUE cranial nerve
  • outgrowth of the brain (part of CNS)
  • covered by meninges (pia, arachnoid, dura)
  • anything injected into the nerve sheath can travel directly to the brain via CSF
  • central retinal artery and vein surround the nerve
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15
Q

oculomotor nerve

A
  • CN III
  • innervates suprior rectus, inferior rectus, inferior oblique, medial rectus, and levator (upper eyelid)
  • primary motor nerve to the extraocular muscles of the orbit (branches superiorly and inferiorly)
  • sends PSNS fibers to the ciliary ganglion - innervate iris sphincter muscles to cause constriction of the pupil
  • SNS motor fibers control pupil dilation
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16
Q

trochlear nerve

A
  • CN IV
  • provides motor fibers to the superior oblique muscle (to keep eye looking straight)
  • only orbital cranial motor nerve that enters the orbit from outside the muscle cone
  • travels in a medial direction to innervate the superior oblique muscle
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17
Q

trigeminal nerve

A
  • CN V
  • sensory and motor components
  • three divisions –> opthalmic, maxillary and mandibular
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18
Q

opthalmic branch of trigeminal nerve

A

-provides sensation of pain, touch, and temperature to the cornea, ciliary body, iris, lacrimal gland, conjunctiva, nasal mucosa, eyelid, eyebrow, forehead and nose

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19
Q

maxillary branch of trigeminal nerve

A

-provides senation of pain, touch and temperature to the upper lip, nasal mucosa, and scalp muscles

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20
Q

three branches of opthalmic nerve

A
  • lacrimal
  • frontal
  • nasociliary
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21
Q

lacrimal nerve

A

innervates lacrimal gland

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22
Q

frontal branch

A

largest branch of opthalmic nerve, further branches

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23
Q

nasociliary nerve

A

sends nerve fibers medially and to the ciliary ganglion

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24
Q

abducens nerve

A
  • CN VI
  • motor function to the lateral rectus muscle
  • helps keep eyes looking straight
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25
Q

facial nerve

A
  • CN VII
  • provides motor function to the facial muscles
  • upper and lower branches
  • upper branch innervates the orbicular muscle, superficial facial and scalp muscles
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26
Q

vagus nerve

A
  • CN X
  • motor function to the intrinsic muscles in the larynx and heart
  • major PSNS visceral innervation
  • efferent pathway for the ocularcardiac reflex
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27
Q

six extraocular muscles

A
  • surround the eye (globe)
  • superior rectus (12 o’clock)
  • inferior rectus (6 o’clock)
  • medial rectus
  • lateral rectus
  • superior oblique
  • inferior oblique
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28
Q

superior rectus

A
  • moves eye upward
  • supraduction
  • CN III (oculomotor)
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29
Q

inferior rectus

A
  • moves eye downard
  • infraduction
  • CN III (Oculomotor)
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30
Q

medial rectus

A
  • moves eyeball nasally
  • adduction
  • CN III (Oculomotor)
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31
Q

lateral rectus

A
  • moves eyeball laterally
  • abduction
  • CN VI (Abducens)
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32
Q

superior oblique

A
  • rotates eyeball on horizontal axis towards nose
  • intorsion, depression
  • CN IV (Abducens)
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33
Q

inferior oblique

A
  • rotates eyeball on horizontal axis temporally
  • extorsion, elevation
  • CN III (Oculomotor)
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34
Q

eyelid muscles

A
  • levator muscle used for raising upper eyelids
  • orbicular muscle contracts eyelid
  • three divisions of muscles arranged around the eyeball (orbital, palpebral, tarsal)
  • akinesia of these muscles is generally desired for ocular procedures
  • contraction of these muscles can increase IOP
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35
Q

anesthesia considerations for opthalmic surgery

A
  • changes in IOP
  • CV response to traction on extraocular muscles
  • absorption of topically administered drugs
  • open eye surgery (GA vs local)
  • succinylcholine increases IOP
  • echotiopate drops
  • complication of expansion of gas bubble
  • post retrobulbar apnea syndrome
  • laser surgery
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36
Q

IOP function

A

maintains normal shape and optical properties of the eye

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37
Q

normal IOP

A

12-20 mmHg

38
Q

determinants of IOP

A
  • aqueous humor dynamics –> balance between production and elimination of aqueous humor
  • changes in choroidal blood volume –> vascular meshwork in posterior chamber
  • rise in venous blood pressure (chronic HTN, not acute changes in BP)
  • extraocular muscle tone
39
Q

aqueous humor

A
  • thin, watery fluid that fills the space in the anterior chamber between the cornea and iris
  • nourishes the cornea and lens
  • gives the front of the eye its form and shape
  • continually produced by ciliary body which lies just behind the iris
  • drains out of the eye via the trabecular meshwork into the aqueous veins and eventually into the veins of the orbit
40
Q

what increases IOP

A
  • blinking (5 mmHg increase)
  • squinting (26 mmHg increase)
  • CV/respiratory variables (CVP, ABP, PaCO2)
  • laryngoscopy and intubation
  • external pressure/positioning
  • succinylcholine
  • topical anticholinergics
41
Q

what decreases IOP

A
  • volatile anesthetics
  • IV anesthetics (except ketamine)
  • NDMR
  • benzos
  • narcotics
42
Q

succinylcholine and IOP

A
  • increases IOP by 5-10 mmHg for 5-10 min
  • mechanism is unlcear
  • may be result of prolonged contraction of extraocular muscles
  • no consistent method to prevent increase
43
Q

oculocardiac reflex efferent and afferent

A

-efferent = trigeminal (CN V)
-afferent = vagus (CN X)
why it is called the “five and dime reflex”

44
Q

why does the oculocardiac reflex occur?

A

pain, pressure or manipulation of the eyeball

COMMON CAUSE = traction of medial rectus muscle

45
Q

symptoms of oculocardiac reflex

A
  • cardiac dysrhythmias (bradycardia, sinus arrest, v-fib, AV block, ventricular ectopy) and negative inotropy
  • transient cardiac arrest occurs in 1:2200 strabismus surgeries
46
Q

most common surgery for oculocardiac reflex

A
  • pediatric strabismus surgery
  • transient cardiac arrest occurs in 1:2200 strabismus surgeries
  • attenuated by pretreatment with anticholinergics
47
Q

treatment of oculocardiac reflex

A
  • stop stimulus
  • administer atropine/glyco
  • infiltration of LA to the medial rectus muscle
48
Q

surgery for detached retina

A
  • small gas bubble injected into posterior chamber to hold retina in place
  • sulfur hexafluoride most commonly used
49
Q

sulfur hexafluoride

A
  • inert poorly diffusible gas
  • much less soluble in blood than nitrogen and N2O
  • DOA is 10 days
  • nitrogen from inhaled air enters bubble faster than SH can diffuse into blood, allowing the bubble to expand (doubles in 24 hours)
  • inhaled 70% N2O can triple the size of the bubble and quickly increase IOP
  • can be reversed if N2O discontinued within 18 minutes, the pressure changes can lead to negative outcomes
  • discontinue N2O 20 min prior to injection to allow for washout
  • avoid N2O for 10 days after SH (5 days if injected air)
50
Q

opthalmic mydriatics

A
  • atropine/scopolamine - anticholinergic; central cholinergic syndrome can occur or disorientation
  • epi - sympathetic agonist; tachycardia, arrhythmias, HTN, HA
  • phenylephrine - alpha agonist; HTN, arrhythmias, HA, reflex bradycardia
  • cyclopentolate - synthetic anticholinergic; disorientation, psychosis, seizures
51
Q

pilocarpine

A
  • muscarinic alkaloid

- miosis, redness, irritation

52
Q

carbachol

A
  • synthetic carbamyl ester of choline

- used if not responsive to pilocarpine

53
Q

physostigmine

A
  • indirect acting anticholinesterase

- miosis

54
Q

echothiopate

A
  • indirect acting organophosphorus cholinesterase inhibitor
  • miosis
  • used for treatment of glaucoma
  • irreversible cholinesterase inhibitor
  • systemic absorption leads to decreased plasma cholinesterase activity
  • lasts 3-6 weeks after d/c
  • succ will be prolonged 20-30 minutes
  • may also prolong mivacurium and ester linked LAs
55
Q

timolol

A
  • potent non-selective beta blocker

- bradycardia, asthma, CHF

56
Q

acetylcholine

A
  • cholinergic agonist

- miosis, bradycardia, bronchospasm, hypotension

57
Q

acetazolamide (diamox)

A
  • use this a lot
  • carbonic anhydrase inhibitor
  • reduces secretion of aqueous from ciliary body, mild diuretic, hypokalemia, acidosis, hematuria, paresthesia, gastric distress, flaccid paralysis, seizures
  • avoid with renal/hepatic disease
  • avoid in those with allergy to sulfa abx
58
Q

local anesthetics

A
  • topical local anesthesia often used for optho surgery
  • most often placed by surgeon
  • toxicity is rare
  • topical agents used = tetracaine, proparacaine, bupivacaine, lidocaine, cocaine
  • blocks = bupivacaine, mepivacaine, lidocaine
59
Q

how do topical eye medications work?

A

enter bloodstream through the outer eye membrane and lacrimal apparatus

60
Q

measures to reduce the amount of med that enters the bloodstream

A
  • close eyes for 60 seconds after drops instilled to encourage absorption by eye
  • avoid blinking
  • block tear outflow canal (place index finger over medial canthus)
61
Q

topical/intraocular anesthesia

A
  • cataract and vitreoretinal surgeries are most frequently performed intraocular procedures
  • topical anesthesia for cataract is effective in providing adequate analgesia
  • intraocular anesthesia with 1% lidocaine
62
Q

ocular regional anesthesia

A
  • most common and effective way to consistently produce analgesia and akinesia of the eye and eyelids
  • ocular local anesthesia - peribulbar block and retrobulbar block
  • anesthetize multiple cranial nerves (III, IV, V, VI, VII)
  • orbital epidural space
  • facial nerve block
63
Q

peribulbar block (PBB)

A
  • injection of LA outside the muscle cone
  • provides analgesia and akinesia of the eye
  • relatively low complication rate
  • many variations on technique
  • patient needs to look straight ahead (avoid vasculature and optic nerve)
  • use a dull, short beveled 25-27G 22 mm needle
  • insert needle in lateral aspect of inferotemporal quadrant and superiornasal
  • do NOT insert beyond 25 mm or pierce muscle cone
  • aspirate before slow injection
  • 6 mL of LA
  • lido + bupi (+/- epi)
64
Q

PBB disadvantages compared to RBB

A
  • large volumes injected (6-8 mL)
  • may increase IOP
  • slower onset of action (5-10 min)
  • possible perforation of globe
  • vertical diplopia (myotoxicity from LA)
65
Q

three injections of PBB

A
  • superior injection
  • medial canthus
  • inferotemporal injection
66
Q

retrobulbar block (RBB)

A
  • injection of LA inside the muscle cone
  • provides analgesia and akinesia of eye
  • higher complication rate than PBB
  • insert 25G needle through lower lid at the junction of the lateral third and medial 2/3 of the inferior orbital edge
  • advance 25-35 mm toward apex of orbit (19-31 mm safest)
  • ASPIRATE and inject 2-5 mL of LA
  • lido and bupi most common
67
Q

complications of RBB

A
  • complications occur in 1:5000 blocks
  • trauma to optic nerve
  • vision loss
  • retrobulbar hemorrhage
  • globe perforation
  • oculocardiac reflex
  • brainstem anesthesia (injection into optic nerve sheath)
  • IV or intra-arterial injection
  • seizure
  • respiratory or cardiac arrest
  • usually occur within 15 min after block
68
Q

RBB contraindications

A
  • bleeding disorders
  • anticoagulation
  • extreme myopia
  • open eye injury
69
Q

sub-tenon’s (episcleral) block

A
  • LA placed into potential space between Tenon’s capsule and the sclera
  • inferonasal conjunctival fornix most commonly used
  • direct needle posteriorly following curve of globe
  • superficial injection allows LA to spread circularly around scleral portion of globe
  • larger volume allows spread to extraocular muscle sheaths
  • deep injection - posterior intra and extra conal spaces (2-5 mL) is most common
70
Q

facial nerve block

A
  • periocular branches of the facial nerve

- done to prevent excessive blinking during surgery

71
Q

percentage of closed claims for optho against anesthesia

A
  • 30% of eye injury claims due to patient movement during opthalmic surgery
  • blindness was outcome in all cases
72
Q

preop considerations for opthalmic surgery

A
  • most procedures can be performed under regional and sedation
  • same standard of care
  • NPO status
73
Q

indications for GA in optho

A
  • pediatric patient
  • patient lack of cooperation
  • severe claustrophobia
  • inability to communicate
  • inability to lie flat
  • open-eye injuries
  • procedures with duration greater than 2 hours
74
Q

intraop management sedation for optho

A
  • short acting agents because usually short procedures
  • prevent cardiac or respiratory side effects
  • meds = fentanyl, alfentanil, remi, midaz, prop, dexmedetomidine
75
Q

optho procedures intraop management

A
  • unnecessary to maintain sedation if block is adequate
  • OR turned 90-180 degrees
  • standard monitors
  • oculocardiac reflex
  • temperature
  • fluids
  • light GA for little stimulation
  • hypotension
  • oxygen and cautery
  • risk of corneal abraision, retinal artery occlusion
76
Q

post-op management of optho procedures

A
  • PONV very common
  • postop eye pain unusual (usually means either a corneal abrasion or acute intraocular HTN that needs to be treated with mannitol or diamox)
  • elderly patients with a history of MI are at increased risk for ischemic events even under LA (consider periop beta-blockers)
77
Q

strabismus surgery

A
  • ocular misalignment
  • most common opthalmic condition requiring surgical repair in children
  • intervention should occur before 4 months to allow normal stereoscopic visual development
  • surgery lengthens/shortens ocular muscles to straighten the eyes and allow binocular vision
  • 30-60 min
  • GA
  • minimal EBL
  • table turned away from you
78
Q

strabismus side effects

A
  • ocularcardiac reflex (increased PaCO2 shown to decrease this during surgery; stop stim, admin anticholinergics, LA infiltration)
  • increased risk of MH
  • associated with underlying myopathy so higher risk of MH (avoid triggers and be vigilant)
79
Q

strabismus and PONV

A
  • 48-85% incidence
  • ocular emetic reflex
  • possible disruption of surgical repair
  • prevention includes hydration, minimize opioids, avoid N2O, propofol, LA infiltration near extraocular muscle, antiemetics (zofran and decadron)
80
Q

penetrating eye injury anesthetic considerations

A
  • full stomach precautions
  • aspiration risk
  • prevent increase in IOP (succ increases within 1 min, peaks at 9 mmHg increase after 6 min; avoid coughing)
  • open globe = succ or no succ; laryngoscopy increases IOP so be mindful, consider NDMR for RSI
81
Q

open globe + full stomach

A
  • emergency surgery with GA
  • dos and dont’s to prevent aspiration
  • do not attempt to evacuate contents using NGT preop
  • do administer metoclopramide, H2 antagonists, non-particulate antacid prior to induction
  • do NOT attempt regional
  • do attempt RSI using cric pressure and avoid PPV
  • DO extubate awake, spontaneously breathing, head turned to side
82
Q

things to prevent increase in IOP

A
  • avoid direct pressure on eye
  • avoid trendelenburg position
  • avoid regional
  • avoid increase in CVP
  • avoid drugs that increase IOP
  • avoid agitation in young children
83
Q

anesthesia complications in optho

A
  • retrobulbar hemorrhage
  • globe puncture
  • optic nerve sheath trauma
  • intravascular injection
  • ocular ischemia
  • extra-ocular muscle palsy and ptosis
  • facial nerve blocks
  • oculocardiac reflex
  • corneal abrasion
  • central retinal artery occlusion
84
Q

retrobulbar hemorrhage

A
  • results from trauma to orbital vessel
  • moves eyeball forward
  • venous hemorrhages have slow onset, arterial has rapid onset
  • lateral canthotomy may be indicated if hemorrhage is not resolved by digital pressure
85
Q

lateral canthotomy

A
  • increase orbital space by cutting lateral canthus
  • reduces orbital pressure that results from hemorrhage
  • place hemostat in temporal direction along lateral canthus 4-6 mm and clamp hemostat
  • use scissors to incise the crush marks left by hemostat
  • control local bleeding
86
Q

globe puncture

A
  • sharp and dull needles both reported to have penetrated eye during injection
  • globe can burst apart from IOP caused by injection
  • risks = miopic eye, scleral thinning, scleral buckling, bulging of sclera
  • prevent = avoid supranasal position of gaze, direct needle away from axis of globe during insertion, insert needle slowly with bevel toward globe, never forecully inject LA, use modified techniques
  • symptoms = increased resistance to injection, dilation/paralysis of pupil, increased IOP, hemorrhage
87
Q

optic nerve sheath trauma

A
  • optic sheath surrounds optic nerve
  • outer sheath = dura mater
  • inner sheath = arachnoid and pia mater
  • subarachnoid space contains CSF and is continuous with optic chiasm
  • dura splits into two layers at optic foramen - inner layer forms dural covering of optic nerve and forms orbital epidural space
  • observe contralateral pupil before block, if contralateral pupil constricted –> dilated after block, assume subarachnoid/subdural injection and prepare for respiratory arrest
88
Q

ocular ischemia

A
  • retinal vascular occlusion or thombosis has been reported after ocular blocks
  • decreased pulsatile ocular blood flow after blocks
  • optic nerve atrophy reported after regional or GA
  • transient symptoms of optic nerve injury include contralateral amaurosis or respiratory arrest; vascular occlusion/thrombosis which may lead to loss of vision
89
Q

extraocular muscle palsy and ptosis

A
  • inferior muscle palsy reported after retrobulbar anesthesia
  • symptom = persistent vertical diplopia
  • surgical intervention may be indicated
  • prevention = avoid needle contact with extraocular muscles, avoid deep orbital penetration, avoid angling needle toward visual axis of globe
  • myotoxocity of LA may cause postop diplopia and or ptosis
90
Q

facial nerve block

A
  • discomfort from block of CN VII
  • bell’s palsy may occur secondary to direct nerve trauma
  • dysphagia, hoarseness, coughing and respiratory distress reported due to paresis of the vagus, glossopharyngeal and spinal accessory nerves
  • prevention = avoid large volume LA, avoid nadbath technique in certain patients, seated/lateral position to protect airway, intubate if airway concerns

N931 Advanced Principles of Anesthesia I (19 decks)

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