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AS - N931 Advanced Principles of Anesthesia > Ophthalmic > Flashcards

Ophthalmic Flashcards

1
Q

What is the leading cause of blindness worldwide?

A

Cataracts

- Leading cause of poor vision in the USA

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2
Q

What is the leading cause of new blindness cases among adults 20-74yo?

A

Diabetes

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3
Q

Eyeball

A

Globe

Adult volume = 30mL

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4
Q

Visual Axis

A

Optic axis - imaginary line from cornea midpoint to retina or macula midpoint
Axial length measures the visual axis

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5
Q

Normal Visual Axis Length

A

23-23.5mm

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6
Q

Hyperopia

A

Farsighted

Globe < 22mm long

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7
Q

Myopia

A

Nearsighted
Axial length >24mm

↑risk globe puncture

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8
Q

Anterior Segment

A

Two chambers:

  1. Anterior
    - Behind the cornea
    - Filled w/ aqueous humor produced by ciliary body
  2. Posterior
    - Contains the lens
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9
Q

Posterior Segment

A

Vitreous humor
Retina
Macula
Optic nerve root

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10
Q

Optic Nerve

A

Cranial nerve II
Optic nerve orbital portion 25-30mm long & travels posteriorly w/in the muscle cone
4mm diameter
NOT A TRUE CRANIAL NERVE
Central retinal artery & vein surround the nerve

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11
Q

What is the optic nerve?

A

Outgrowth of the brain
Covered by meninges - pia, arachnoid, dura
Anything injected into the nerve sheath can travel directly to the brain via CSF

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12
Q

Oculomotor Nerve

A

Cranial nerve III
Innervates the superior rectus, inferior rectus, inferior oblique, medial rectus, & levator
1° motor nerve to the extraocular orbit muscles
Sends PSNS fibers to the ciliary ganglion - innervate iris sphincter muscles to cause pupil constriction
SNS motor fibers control pupil dilation

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13
Q

Trochlear Nerve

A

Cranial nerve IV
Provides motor fibers to the superior oblique muscle
Only orbital cranial motor nerve that enters the orbit from outside the muscle cone
Travels in medial direction to innervate the superior oblique muscle

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14
Q

Trigeminal Nerve

A

Cranial nerve V
Sensory & motor
Intracranial portion forms the trigeminal ganglion
- Ophthalmic, maxillary, & mandibular divisions

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15
Q

Ophthalmic Nerve

A

Trigeminal nerve branch
Provides pain, touch, & temperature sensation to the cornea, ciliary body, iris, lacrimal gland, conjunctiva, nasal mucosa, eyelid, eyebrow, forehead, & nose
- Lacrimal, frontal, & nasociliary
Frontal = largest branch
Nasociliary sends nerve fibers medially & to the ciliary ganglion

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16
Q

Maxillary Nerve

A

Trigeminal nerve branch

Provides pain, touch, & temperature sensation to the upper lip, nasal mucosa, & scalp muscles

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17
Q

Abducens Nerve

A

Cranial nerve VI

Motor function to the lateral rectus muscle

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18
Q

Facial Nerve

A

Cranial nerve VII
Provides motor function to the facial muscles
Upper & lower branches
Upper branch innervates the orbicular muscle, superficial facial, & scalp muscles

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19
Q

Vagus Nerve

A

Cranial nerve X
Motor function to the intrinsic muscles in the larynx & heart
PSNS visceral innervation
*Efferent pathway for oculocardiac reflex

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20
Q

Extraocular Muscles

A
  1. Superior rectus - moves the eye upward
  2. Inferior rectus - moves eye downward
  3. Medial rectus - moves eye nasally
  4. Lateral rectus - moves eye laterally
  5. Superior oblique - rotates eye on horizontal axis towards the nose
  6. Inferior oblique - rotates eyeball on horizontal axis temporally
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21
Q

Superior Rectus

A

Cranial nerve III

Supraduction

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22
Q

Inferior Rectus

A

Cranial nerve III

Infraduction

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23
Q

Medial Rectus

A

Cranial nerve III

ADduction

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24
Q

Lateral Rectus

A

Cranial nerve VI

ABduction

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25
Q

Superior Oblique

A

Cranial nerve IV

Intorsion, depression

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26
Q

Inferior Oblique

A

Cranial nerve III

Extorsion, elevation

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27
Q

Normal IOP

A

10-20mmHg

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28
Q

What determines IOP?

A

Aqueous humor dynamics - balance b/w production & elimination
Changes in choroidal blood volume - vascular meshwork in the posterior chamber
↑venous blood pressure
Extraocular muscle tone

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29
Q

Aqueous Humor

A

Thin, watery fluid that fills the space in the anterior chamber b/w the cornea & iris
- Nourishes the cornea & lens
- Gives the anterior eye form & shape
Continually produced by the ciliary body (lies behind the iris)
Drains out via trabecular meshwork into the aqueous veins & then into orbit veins

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30
Q

↑IOP

A 
Eyelid muscle contraction
Blinking 5mmHg
Squinting 26mmHg
Cardiovascular or respiratory variables (CVP, ABP, PaCO2)
*Laryngoscopy & intubation
External pressure
Positioning - prone
Succinylcholine
Topical anticholinergics
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31
Q

↓IOP

A 
Volatile anesthetics
IV anesthetics (exception: Ketamine)
Non-depolarizing muscle relaxants
Benzodiazepines
Narcotics
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32
Q

Succinylcholine

A

↑IOP 5-10mmHg for 5-10 minutes
MOA unclear
Result from prolong extraocular muscle contraction?
No consistent method to prevent increase
Pediatric laryngospasm dose 4mg/kg IM or 1-2mg/kg IV (10mg)

33
Q

Oculocardiac Reflex

A

Afferent transmission via Trigeminal nerve V
Efferent transmission via Vagus nerve X

Pull on muscle → bradycardia
Causes - pain, pressure, or eyeball manipulation
Traction on medial rectus muscle common

34
Q

Oculocardiac Reflex S/S

A 
Cardiac dysrhythmias (bradycardia, sinus arrest, V-fib, AV block, ventricular ectopy)
Negative inotropy
35
Q

During what surgery does the oculocardiac reflex most commonly occur?

A

Pediatric strabismus surgery

36
Q

Oculocardiac Reflex Treatment

A

Anticholinergics pre-treatment (?)
Stop the stimulus or release pressure
Administer Atropine 10mcg/kg or Glycopyrrolate
LA infiltration into medial rectus muscle

37
Q

Detached Retina Surgical Repair

A

Small gas bubble injected into posterior chamber to hold retina in place
Sulfur hexafluoride most commonly used
- Inert, poorly diffusible gas
- Less soluble in blood than nitrogen & N2O
- DOA 10 days
Bubble expands 2x in 24 hours
Discontinue N2O 20 minutes prior to injection to allow washout
Avoid N2O 10-14 days after sulfur hexafluoride

38
Q

Echothiophate

A 
IRREVERSIBLE cholinesterase inhibitor
Glaucoma treatment
Systemic absorption → ↓plasma cholinesterase activity
Lasts 3-6 weeks after discontinuation
Succinylcholine prolonged 20-30 minutes
Extend ester local anesthetics duration
39
Q

Topical Eye Medications

A

Enter bloodstream via outer eye membrane & lacrimal apparatus
Close eyes 60 seconds after gtt instilled to improve absorption
Avoid blinking
Block tear outflow canal (place finger over medial canthus)

40
Q

What are the most commonly performed intraocular procedures?

A

Cataract & vitreoretinal surgeries

41
Q

Ocular Regional Anesthesia

A

Peribulbar block
Retrobulbar block
Facial nerve block

42
Q

Peribulbar Block

A

Inject LA outside the muscle cone
Injection above and/or below orbit
Provides eye analgesia & akinesia
Typically more patchy - requiring additional supplementation throughout the case (request surgeon admin more LA)
Relatively low complication rate
Safer choice d/t less hemorrhage & central spinal risk

43
Q

Peribulbar Block

Disadvantages

A 
↑volumes injected 6-8mL
↑IOP
Slower onset (5-10 minutes)
Possible globe perforation
Vertical diplopia (myotoxicity from LA)
44
Q

Peribulbar Block

Technique

A

Patient looks straight ahead
Avoid vasculature & optic nerve
Dull, short-beveled 25-27G 22mm needle
Insert needle lateral aspect of the inferotemporal quadrant & superior-nasal
ASPIRATE slowly before injection
Inject 6mL local anesthetic
Lidocaine + Bupivacaine (+/- Epi 1:400,000)

45
Q

Retrobulbar Block

A

Inject LA inside the muscle cone
Provides eye analgesia & akinesia* (better akinesia for surgeon)
↑complication rate as compared to peribulbar block
Hemorrhage risk d/t anesthetic injection inside the muscle cone

46
Q

Retrobulbar Block

Technique

A

Insert 25G needle through lower lid at lateral third junction & medial 2/3 inferior orbital edge
Advance 25-35mm (19-31mm safest) toward orbit apex
ASPIRATE & inject 2-5mL local anesthetic
Lidocaine & Bupivacaine most common

47
Q

Retrobulbar Block

Complications

A 
1:500 blocks
Trauma to optic nerve
Vision loss
*Retrobulbar hemorrhage 
Globe perforation
Oculocardiac reflex
Brainstem anesthesia (injection into optic nerve sheath)
- Central LA spread to CSF causing hemodynamic instability & respiratory depression w/in 5min
IV or intra-arterial injection
Seizure
Respiratory or cardiac arrest
*Usually occur w/in 15 minutes after block
48
Q

Retrobulbar Block

Contraindications

A

Bleeding disorders
Anticoagulation
Extreme myopia
Open eye injury

49
Q

Sub-Tenon (Episcleral) Block

A

Local anesthetic placed into potential space b/w tenon’s capsule & sclera
Inferonasal conjunctival fornix most commonly used
Direct needle posteriorly following globe curve
Superficial injection allows LA to spread circularly around scleral globe portion (3-5mL)
Larger volume (8-11mL) allows spread to extraocular muscle sheaths
Deep injection - posterior intra & extraconal spaces (2-5mL) most common

50
Q

Facial Nerve Block

A

Facial nerve periocular branches

Prevent excessive blinking during eye surgery

51
Q

What are indications for general anesthesia?

A 
Pediatric patient
Uncooperative patient
Severe claustrophobia
Inability to communicate
Inability to lie flat
Open-eye injuries
Procedures w/ duration > 2 hours
52
Q

General Anesthesia

Disadvantages

A 
Nausea/vomiting
↑IOP
Aspiration
Complications 2° to medical problems (i.e. cardiovascular disease)
Time 
\$\$$
53
Q

Medication Considerations

A

Synergistic effects
Pediatric/elderly dosing
Circulation time

54
Q

Intraop Management

A 
Block sedation (short-acting agents)
Sedation not required w/ adequate block
Rotate HOB 90-180° 
Standard monitors
Oculocardiac reflex
Temperature
Fluids
Consider "light" GA w/ stimulation
Hypotension
Oxygen & cautery → airway fire risk
Corneal abrasion risk
Retinal artery occlusion
55
Q

Postop Management

A

PONV (especially pediatrics)
Postop eye pain unusual - indicates corneal abrasion or acute intraocular HTN (treat w/ Mannitol or Acetazolamide)
Elderly patients w/ MI history ↑risk ischemic events even under LA - consider periop β blockers

56
Q

Strabismus

A

Ocular misalignment
Intervention before 4mos to allow normal stereoscopic visual development
↑MH risk associated w/ underlying myopathy
Avoid triggers

57
Q

What is the most common ophthalmic condition requiring surgical repair in children?

A

Strabismus

58
Q

Strabismus Surgical Correction

A

Lengthens/shortens ocular muscles to straighten eyes & allow binocular vision
30-60 minutes
General anesthesia
Minimal EBL
PONV prevention - hydration, ↓opioids, avoid N2O, Propofol, LA infiltration near extraocular muscle, antiemetics (Decadron 0.1mg/kg or Zofran 0.1mg/kg)
Painful procedure - Tylenol 15mg/kg, Toradol 0.5mg/kg, & Fentanyl 1-3mcg/kg

59
Q

Penetrating Eye Injuries

A

Full stomach precautions
Aspiration risk
Prevent ↑IOP

60
Q

Open Globe

A 
Full-thickness cornea (transparent outer covering) or sclera (white outer covering) defect 
Emergency surgery w/ GA
Succinylcholine risk vs. benefit
Laryngoscopy & intubation ↑IOP
Antibiotics - Vancomycin & Zosyn
61
Q

Aspiration Prevention

A

Do NOT attempt to evacuate contents w/ NG tube preop
Admin Metoclopramide IV, H2 antagonists (Ranitidine), and/or non-particulate antacid prior to induction
Do NOT attempt regional anesthesia LA injection ↑IOP
Attempt RSI w/ cricoid pressure & avoiding PPV
Extubate awake, spontaneously breathing, & head turned to side

62
Q

Prevent ↑IOP

AVOID

A 
AVOID direct pressure on eye
AVOID Trendelenburg position
AVOID regional anesthesia
AVOID ↑CVP
AVOID drugs ↑IOP
AVOID agitation in young children
63
Q

Ophthalmic Anesthesia Complications

A 
Retrobulbar hemorrhage
Globe puncture
Optic nerve sheath trauma
IV injection
Ocular ischemia
Extraocular muscle palsy & ptosis
Facial nerve blocks
Oculocardiac reflex
Corneal abrasion
Central retinal artery occlusion d/t prolonged pressure
64
Q

Complications

Retrobulbar Hemorrhage

A

Results from trauma to an orbital vessels
Moves eyeball forward
Venous hemorrhage - slow onset
Arterial - rapid onset & pronounced proptosis

Treatment:

  • Digital pressure
  • Lateral canthotomy (cut lateral canthus) ↑orbital space → place hemostat in temporal direction along lateral canthus 4-6mm & clamp hemostat, use scissors to incise the crush marks left by hemostat, control local bleeding
65
Q

Complications

Globe Puncture

A

↑IOP caused by injection (sharp or dull needles)
Risks include myopic eye, scleral thinning, scleral buckling, & sclera bulging
Prevention - avoid supranasal gaze position, direct needle away from globe axis during insertion, insert needle slowly w/ bevel towards globe, never forcefully inject LA, use modified techniques
S/S ↑resistance to injection, pupil dilation/ paralysis, ↑IOP, hemorrhage

66
Q

Complications

Optic Nerve Sheath Trauma

A

Optic nerve sheath surrounds the optic nerve
- Outer sheath contains dura mater
- Inner sheath consists arachnoid & pia mater
Subarachnoid space contains CSF & continuous w/ optic chiasm
Dura splits into 2 layers at optic foramen
Inner layer forms optic nerve dural covering & forms orbital epidural space
*Observe contralateral pupil block
Contralateral pupil constricted → dilated after block → assume subarachnoid/subdural injection & prepare for respiratory arrest

67
Q

Complications

Ocular Ischemia

A

Retinal vascular occlusion or thrombosis reported after ocular blocks
↓pulsatile ocular blood flow after blocks
Optic nerve atrophy reported after regional block or GA
Transient optic nerve injury symptoms - include contralateral amaurosis or respiratory arrest or vascular occlusion/thrombosis → vision loss

68
Q

Complications

Extraocular Muscle Palsy & Ptosis

A

Inferior muscle palsy reported after retrobulbar anesthesia
Persistent vertical diplopia (double vision)
Surgical intervention indicated
Prevention - avoid needle contact w/ extraocular muscles, avoid deep orbital penetration, avoid angling needle toward visual globe axis
LA myotoxicity may cause postop diplopia and/or ptosis

69
Q

Complications

Facial Nerve Block

A

Cranial nerve VII
Bell’s palsy 2° to direct nerve trauma
S/S - dysphagia, hoarseness, coughing & respiratory distress
Vagus, glossopharyngeal, & spinal accessory nerves close proximity

Prevention:

  • Avoid large volume LA
  • Avoid Nadbath block technique in certain patients
  • Airway concerns → intubate
70
Q

Bells Phenomenon

A

When the eyeballs move upward & outward in response to the eyes being forcefully closed
Protective reflex to prevent corneal injury
AKA “belling”
Requires MAC 1.8 to abolish this reflex

71
Q

Fluorescein

A 
EUA
Dye used to visualize the retina images & leaks around corneal surgical sites
Dose 5-7mg/kg
IV push fast (similar to Adenosine)
Wear gloves when prepare & admin
72
Q

Retinoblastoma

A 
Ocular retina cancer
1° affects children < 4yo
Tumor present in the eye or bilateral
Curable, but ↑risk cancers later in life
Monthly check-ups
EUA → laser or cryotherapy
73
Q

Amblyopia

A

Lazy eye
Children 0-7yo
Initial treatment w/ eye patches or dilation drops on the stronger eye to force the weaker eye to work

74
Q

Corneal Transplant Melts

A

Corneal transplant rejected or suture to the eye has come undone, leaving an opening to the eye
General anesthesia
LMA or ETT dependent on melt severity
Surgical treatment - few sutures or completely remove the original transplant & replace w/ new one

75
Q

Canaliculi Repairs

A

Inner or outer canthus repair
Common in younger children from dog bites or scratches
Fairly quick procedure
Performed by plastic surgery resident

76
Q

Endopthalmitis

A

Tissue or fluid infection INSIDE the eyeball
Surgery performed after patient not responded to conservative measures → infection now in the vitreous
Vitrectomy performed by retina surgeon to remove infected vitreous gel & inject antibiotics into the eye
Possible peribulbar block however not effective in severe infections

77
Q

Tetracaine

A 
Local anesthetic gtt
Numbing eye drops
- Eye only holds 0.5mL
- Admin 2-6 drops divided in doses 1-2min apart
Utilize w/ PRN sedation
78
Q

Diamox

A

Acetazolamide
Carbonic anhydrase inhibitor used to lower IOP
↓aqueous humor production in anterior eye
Adult dose 150-500mg
Mix w/ NS
Admin at end procedure
IV incompatible w/ Zofran
Contraindicated in patients w/ Sulfa allergies

AS - N931 Advanced Principles of Anesthesia (17 decks)

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