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Advanced Anes. Spring 21 > Eye Surgery > Flashcards

Eye Surgery Flashcards

1
Q

Sclera

A

outermost layer
tough, fibrous, white of the eye
cornea - most anterior part

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2
Q

Focus power

A

from curvature of cornea

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3
Q

Middle Layers of the Eye

A

choroid
ciliary body
iris

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4
Q

Choroid

A

layer of blood vessels

located posteriorly

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5
Q

Ciliary Body

A
  • behind iris, produces aqueous humor

- adjusts focus on lens by reducing tension on suspension fibers or zonules of the lens

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6
Q

Iris

A

pigmented, controls light entry

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7
Q

Iris: Parasympathetic Stimulation

A
  • iris sphincter muscle contracts

- miosis = pupillary constriction

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8
Q

Iris: Sympathetic Stimulation

A
  • Iris dilator muscle contracts

- mydriasis or dilatation

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9
Q

Innermost Layer of the Eye

A

Retina

  • photoreceptors –> neural firing
  • no capillaries –> choroid layer gives o2 (detachment can cause vision loss)
  • pars plana –>area btwn edge of cornea and end of retina
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10
Q

Where does safe entry for vitrectomy occur?

A

Pars Plana

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11
Q

Center of the eye

A
  • vitreous gel
  • attaches to vessels and optic nerve
  • traction of vitreous on retina = detachment
  • vitrectomy tx for scarring, bleeding or opacification
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12
Q

OCR

A

Ocular Cardiac Reflex
cause: globe pressure or traction of extraocular muscles or any orbital contents
s/s: bradycardia, AV block, ventricular ectopy, asystole
-more frequent in peds

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13
Q

Which muscle manipulation is seen commonly with OCR?

A

medial rectus traction

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14
Q

Which nerve is involved with triggering OCR?

A

trigeminal-vagal reflex

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15
Q

What factors can worsen OCR response?

A

hypoxia and hypercarbia

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16
Q

OCR Tx

A
  1. Ask surgeon to stop, asses, deepen anesthetic
  2. If persists - atropine
  3. consider robinul
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17
Q

Pretreatment for OCR?

A

atropine or robinul, esp if pt has conduction block or BB

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18
Q

Blood supply to the eye is dependent on…

A

Intraocular perfusion pressure

MAP - IOP

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19
Q

What regulates IOP?

A

amount of aqeous and blood volume

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20
Q

Normal IOP

A

10-22 mmHg

> 25 is pathological

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21
Q

Productino of aqeous humor?

A

constant, regulated by carbonic anhydrase

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22
Q

IOP: Arterial Pressure

A
  • sudden increase in B/P–> increase IOP, drains quick

- sudden decrease in B/P–> drop IOP, loss of autoreg

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23
Q

IOP: Venous Pressure

A
  • increased CVP increases IOP (more than B/P does)

- coughing –> no drain –> increase IOP up to 40x

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24
Q

IOP: Respiration & CO2 tension

A

Decreased PaCO2 –> fast drop in IOP (choroidal vasoconstriction)
Increased PaCO2–> slow increase in IOP
*fast RR may increase IOP from insufficient venous drainage

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25
Q

IOP: Acid Base

A

Metabolic Acidosis –> decreases choroid vessel volume, therefore IOP

Metabolic Alkalosis–> increases the choroid volume and IOP

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26
Q

IOP: External Forces

A

lid retraction
blocks
hemorrhage
etc..

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27
Q

IOP: Anesthetic Drugs

A

-most lower or do not effect IOP
-inhalation agents–> lower B/P, therefore choroidal vol
relax muscles
pupil constriction - enables aqueous outflow

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28
Q

IOP: IV agents

A

propofol- decreases IOP
ketamine - may increase (raise b/p, doesnt relax muscles
etomidate - myoclonus, maybe not a good idea
opioids - generally decrease IOP

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29
Q

IOP: Muscle Relaxants

A
  • intubation will increase IOP (b/p) regardless of NMB if pt isnt deep enough
  • NDNMB do not alter IOP (except curare - decrease)
  • Sch increases IOP
30
Q

IOP: Succinycholine

A

increase IOP
starts w/i 1 minute
-increases 5-10 mmHg for 5-10 mins due to contraction
-glaucoma pt rxn is about the same

31
Q

Acetazolamide (Diamox)

A
  • carbonic anhydrase inhibitor
  • decreases aqueuos production - inhibits Na pump responsible
  • decreases IOP
  • dose = 500 mg, acts w/i minutes
32
Q

What should you watch for with use of acetazolamide (diamox)?

A
  • lyte disturbances

- chronic use depletes K, Na and bicard –> met acidosis

33
Q

Mannitol

A
  • osmotic diuretic
  • can use intraop to drop IOP
  • increases circulating blood volume (CHF)
  • max effect 30-45 min, baseline within 5-6 hrs
34
Q

Topical eye drop absorption

A

subq < topical eye < IV

35
Q

Echothiophate

A
  • topical anticholinesterase drug

- maintains miosis, for glaucoma

36
Q

Caution with echothiophate…

A
  • systemic absorption –> total inhib of plasma cholinesterases (think sch, bad)
  • may dispose to ester-type local toxicity
  • long acting, 4-6 weeks until normal enzyme activity
37
Q

Phenylephrine

A
  • used topically to dilate pupil

- alpha adrenergic agonist

38
Q

Drugs used to constrict pupil…

A

pilocarpine & acetycholine

  • cholinergic drugs
  • bronchospasm and acute bradycardia reported
39
Q

Timolol

A
  • beta blocker, used topically to reduce IOP

- systemic absorption –> brady, bronchospasm, CHF exacerbation

40
Q

Flomax (Tamsulosin hydrochloride)

A

-selective alpha antagonistic properties
-binds to iris dilator muscles
-effects iris dilation and complicates surgery
“floppy iris” 7-24 days after d/c

41
Q

Preop Indications: EKG

A

-new chest pain, decreased exercise tolerance, palpitations, near syncope, fatigue, etc.

42
Q

Preop Eval: HTN

A

-severe HTN –> postop complications
stage 3 = syst > 180 or diast >110
-reschedule until 2 wks of antihtn therapy

43
Q

Preop Eval: DM

A

-check fasting BG, use insulin to maintain BG 150-250

44
Q

Preop Eval: Steroid Use

A
  • don’t usually need stress dose, just use regular

- may need if unexpected hypotension, fatigue and nausea

45
Q

Critical Lyte Results

A

Na < 120 or > 158

K < 2.8 or > 6.2

46
Q

Urea Nitrogen

A

s/s renal decompensation

-critical if > 104

47
Q

Polydipsia, polyuria, wt loss…

A

-check BG

critical if < 46 or > 484

48
Q

H&H critical result

A

Hct < 18% or > 61%

Hgb < 6.6 or > 19.9

49
Q

Hemorrhage potential

A

serious –> orbital and oculoplastic
intermed–> vitreoretinal, glaucoma, corneal transplant
least–> cataract surgery

50
Q

Is if safe to perform cataract surgery if pt is on warfarin?

A

Yes, most agree it is safe

51
Q

Regional Techniques

A

akinesia (immobility)
lessens nausea, keeps em comfy
midaz, fent, prop

52
Q

Facial Nerve Block

A
  • useful when complete immobility of eyelids is necessary

- blocks: orbicularis oculi

53
Q

Facial Blocks Typically used…

A
  1. Van Lint
  2. Atkinson
  3. O’Brien

biggest risk is subcutaneous hemorrhage

54
Q

Nadbath Rehman Blocks

A
  • type of facial block - blocks entire trunk of facial nerve - expect facial droop for several hours
  • close to vagus and glossopharyngeal - associated with vocal cord paralysis, laryngospasm, dysphagia and resp distress
55
Q

Retrobulbar Block

A
  • LA injected into muscle cone
  • Atkinson needle, 1:1 mix bupivacaine 0.75% and lidocaine 2% plain
  • result: anesthesia to globe, akinesia of extraocular muscle (drop IOP)
  • superior rectus muscle may not be blocked –> intorsion on downward gaze
56
Q

RBB Complications

A
  • retrobulbar hemorrhage is most common
  • OCR!
  • proptosis (downward displacement)
  • IV injection
  • arterial injection
  • optic nerve injection
  • ocular perforation
  • post-op strabismus from local tox
57
Q

What monitoring is specific to and mandatory for RBB?

A

IOP, if no elevation then may proceed

58
Q

RBB Optic Nerve injection

A
  • optic nerve sheath is continuous with subarachnoid space–>
  • contralateral amaurosis (no vision)
  • obtundation
  • resp arrest (occurs w/i 20 mins, resolves in 1 hr)
  • vascular collapse (total spinal, medulla)
59
Q

RBB Post Operative Strabismus

A
  • from myotoxicity (bupivicaine)

- day after surgery -> vertical, double vision worsening over 2 months

60
Q

RBB Contraindications

A
  • bleeding disorders
  • extreme myopia (longer glober = more risk)
  • open eye injury
61
Q

Peribulbar Block

A
  • safer, less risk of RB hemorrhage
  • multiple injection around eye, none to muscular cone
  • onset = 9-12 min
  • less complete akinesia
  • more bruising
62
Q

Sub-Tenon’s Block

A
  • tennon’s fascia - surrounds globe and extraocular muscles
  • LA diffuses into retrobulbar space
  • blunt cannula
  • less complications
63
Q

Topical

A
  • ok for small incision and phacoemulsion

- tetracaine 0.5% and lidocaine 4%

64
Q

Ways to limit IOP response to larygoscopy

A

lidocaine 1.5 mg/kg
fentanyl 1-3 mcg/kg
alfentenil 20 mcg/kg
remifentanil 0.5-1 mcg/kg

65
Q

Which procedure is emesis common after? Why?

A

Strabismus surgery, d/t vagal stim

66
Q

Painful eye surgeries

A

scleral buckling
enucleation
open globe repair

67
Q

Nitrous Oxide and Sulfur Hexaflouride

A
  • d/c 15 minutes prior

- avoid for 7-10 days after

68
Q

Nitrous Oxide and Perfluoropropane (C3F6)

A

-avoid nitrous for a month

69
Q

Strabismus surgery

A
  • extraocular
  • shorten and lengthen opposite muscle
  • OCR
  • oral rae, avoid Sch
70
Q

Retinal Detachment

A

extraocular

1-2 hrs

71
Q

Vitrectomy

A

intraocular
gas bubble placed
1-2 hrs

Advanced Anes. Spring 21 (7 decks)

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