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Anesthesia Misc > Ophthalmic Anesthesia > Flashcards

Ophthalmic Anesthesia Flashcards

1
Q

Nerves that innervate the upper lid

A

supraorbital
supratrochlear
lacrimal
zygomaticotemporal

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2
Q

Nerves that innervate the lower lid

A

Zygomaticofacial

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3
Q

Nerves that innervate the globe

A

Long ciliary

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4
Q

Nerves that innervate the medial canthus

A

Infratrochlear

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5
Q

Nerves that innervate the lateral canthus

A

Zygomaticofacial

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6
Q

Indications for retrobulbar block

A

Intraocular surgery
Corneal surgery
Evisceration, enucleation

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7
Q

Complications of a retrobulbar block: orbital

A
  • Corneal abrasions
  • Chemosis
  • Ecchymosis
  • Retrobulbar hemorrhage
  • Globe perforation
  • Optic N damage
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8
Q

Complications of retrobulbar block: systemic

A
  • Manifestation of OC reflex
  • LA toxicity
  • IV/intrathecal injection complications ie seizures, brainstem ax, CPA
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9
Q

RBA: volumes recommended

A

Dogs: 2-3mL
Cats: 1mL
No widely agreed volume/local agent for recommended use

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10
Q

RBA: important to note

A
  • does not provide complete analgesia of eyelids bc some branches of ophthalmic/maxillary N pass intraconally
  • Must combine with eyelid, conjunctival infiltration for enucleation/evisceration
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11
Q

RBA: ITP Approach

A
  • Dogs
  • 22g, 3.81cm spinal needle bent at midpoint at approx 20* angle
  • Inserted through lower lid at junction of middle and temporal thirds
  • Needle advanced until slight pop detected –> piercing of orbital fascia
  • Needle then advanced another 1-2cm dorsally, nasally
  • Reported 1-2mL 2% lidocaine
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12
Q

RBA: superior nasal approach

A
  • Cats
  • 22g, 3.81cm spinal needle bent at midpoint at approx 20* angle
  • Needle inserted through the upper eyelid at dorsomedial orbit
  • Needle advanced 3/4” length toward caudal pole of the globe
  • Inject 1mL LA
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13
Q

PBA approach: canine

A

ventrolateral, medial canthus, dorsomedial +VL orbit
Want to scrape the bony orbit when pass needle
Small dogs: 25g, 5/8” needle
Medium to large breeds: 23g, 1” needle
Giant breeds: 23 1-1.5” needle
0.2-0.8mL/kg with larger dose in small breed dogs, smaller dose in large breed dogs DT body surface area to volume ratio

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14
Q

PBA approach: cats

A

DM single injection
25g 5/8” needle inserted in close proximity to the orbital wall
Up to 4mL but watch toxicity –> may need to dilute further

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15
Q

Peribulbar block

A
  • Gold standard in human medicine

- Has replaced RBA bc the needle is further away from the globe and other intraconal structures

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16
Q

Indications for a PBA

A

-Intraocular surgery

17
Q

Complications of PBA

A
  • Transient increase in IOP –> not a concern if enucleation planned but should not be used in animals with glaucoma or globes at risk of rupture
  • Exophthalmos
  • Chemosis, ecchymosis from rostral spread of injectate volume, damage to small blood vessels
  • Large volume required for adequate intraconal distribution may exceed maximal LA dose in small/cachexic K9, Fl
18
Q

Sub-Tenon’s Anesthesia (STA)

A
  • Safer alternative to needle-based techniques
  • Blunt cannula inserted under sterile conditions along curvature of sclera into Tenon’s space via small incision in the conjunctiva and Tenon’s capsule several mm from the limbus
  • LA diffuses along Tenon’s space to block short and long ciliary nerves to produce pupil dilation (short) and analgesia (long)
19
Q

STA in Dogs

A
  • incision in DM portion of bulbar conjunctiva, 5mm from the limbus
  • 19g STA cannula inserted
  • Incision allowed to heal by second intention
20
Q

Consequences of postoperative ophthalmic pain

A
  • self-trauma

- possible dehiscence of surgical site

21
Q

Perioperative pain management of ophthalmic procedures in dogs and cats

A
  • Systemic use of opioids +/- NSAIDS

- regional anesthesia blocks nociception –> More complete analgesia than systemic analgesics

22
Q

Goal of regional anesthesia

A

Reduce need for preoperative administration of systemic analgesics
Also reduces requirements for GA during surgery

23
Q

Other benefits of regional anesthesia during ocular surgery

A
  1. Akinesia of extra ocular muscles, resulting in globe centralization
  2. Mydriasis may facilitate some ophthalmic procedures
  3. Trigeminal N, ciliary ganglion block may decrease incidence of oculocardiac reflex –> bradycardia, systole
24
Q

Orbit

A

In carnivores, incomplete
-medial orbit present with a partial orbital rim
Bony extensions of the orbital rim longer in cats > dogs
DL component replaced by supraorbital ligament - more extensive in dogs > cats

25
Q

Tenon’s Capsule

A

-Thick connective tissue enclosing the sclera

26
Q

Tenon’s Space

A

-Space btw sclera and Tenon’s capsule
-Filled with loose connective tissue
AKA episcleral space

27
Q

Extraocular muscles

A
  • provide globe motility
  • Forms cone behind eye –> orbital structures, drug application described in relation to the cone as intraconal (inside the cone) or extraconal (outside the cone)
28
Q

CN II

A

Optic N
Intraconal
Vision, light reflexes

29
Q

CN III

A

Oculomotor N
Intraconal
Iris sphincter, dorsal/ventral/medial recti, ventral oblique. levator palpebrae superioris m

30
Q

CN IV

A

Trochlear N
Extraconal
Dorsal oblique m

31
Q

CN V

A

Trigeminal N –> ophthalmic (V1), maxillary (V2) branches

  • Intra and extraconal
  • Sensory to globe, orbit, eyelids
32
Q

CN IV

A
  • Abducens N
  • Intraconal
  • Lateral rectus, retractor bulbi muscles
33
Q

CN VII

A
  • Facial N
  • Outside the orbit
  • Orbicularis oculi m
34
Q

Globe

A

-Globe size correlate with breed, size, dog BW

35
Q

Globe diameter K9

A

20-22mm

36
Q

Globe diameter FL

A

~21mm

Cats have huge globes compared to their body size

37
Q

Orbital Tissue nerve supply

A

-Supplied with motor, sensory, autonomic innervation

38
Q

Optic N

A

CN II –> covered with meninges, CSF

Vision fibers, pupillomotor fibers responsible for PLR and dazzle reflex

Anesthesia Misc (3 decks)

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