Apex- misc: eyeballs

Question 1

Identify the statement htat BEST represents the anesthetic considerations of opthalmic surgery:

A. Intraocular perfusion pressure = MAP-CVP
B. Aqueous humor is reabsorbed by the ciliary process
C. Hypocarbia increases IOP
D. N20 is contraindicated for 10 days after a sulfur hexafluoride bubble is placed

Answer 1

D.

Intraoccular perfusion pressure = MAP - IOP
Aqueous humor is PRODUCED by the ciliary process (reabsorbed in the canal of Schlemn)
HYPERCARBIA increaes IOP

Question 2

Normal IOP

Answer 2

10-20mmHg

Question 3

T/F: increased IOP in a patient with an open globe injury can cause permanent blindness

Answer 3

True

Question 4

T/F: Sux is okay to use in a patient with an open eye injury and a full stomach

how much does it increase IOP by and for how long?

what else could you use?

Answer 4

True

5-15mmHg for up to 10 mins

Roc 1.2mg/kg

Question 5

What does a chornically elevated IOP that leads to retinal artery compression cause?

Answer 5

Glaucoma

Question 6

IOP is reduced by drugs that do one of two things:

Answer 6

1. reduce aqueous humor production (ciliary)
2. facilitate aqueous humor drainage

Question 7

What kind of surgery corrects the misalignment of the extraocular muscles and re-establishes the visual axis?

2 unique anesthetic considerations for this procedure

Answer 7

Strabismus surgery

PONV and oculocardiac reflex

Question 8

Nitrous is contraindicated for how long after SF6 bubble placement?

when it that bubble be used?

Answer 8

7-10 days after

it’s placed over the retina during retinal reattachment, vitrectomy, and macular hole repair

Question 9

Aterial supply to the eye

venous supply from the eye

Answer 9

ICA > Opthalmic Artery > Central Retinal artery & Posterior cilliary arteries

Opthalmic veins > cavernous sinus

Question 10

Intraocular perfusion pressure =

Answer 10

Map - IOP

10-20mmHg = normal IOP

Question 11

Aqueous humor is produced by what (where)

Aqueous humor is reabsorbed by what (where)

Answer 11

Produced by the ciliary process (posterior chamber) (CP/PC)

Reabsorbed by the canal of Schlemm (Anterior Chamber) (anterior - a, ashley schlemm)

Question 12

Increase/Decrease/No effect on IOP:

Volatile anesthetics

Answer 12

Decrease

(decrease CVP/MAP)

Question 13

Increase/Decrease/No effect on IOP:

Nitrous oxide

Answer 13

decrease - unless in combination with SF6 bubble, than increase

Question 14

Increase/Decrease/No effect on IOP:

Hypothermia

Answer 14

decrease

Question 15

Increase/Decrease/No effect on IOP:

NDMRs

Answer 15

decrease

Question 16

Increase/Decrease/No effect on IOP:

propofol

Answer 16

decrease

Question 17

Increase/Decrease/No effect on IOP:

Anticholinergics

Answer 17

No effect

Question 18

Increase/Decrease/No effect on IOP:

LMA placement/removal

Answer 18

minimal effect

Question 19

Increase/Decrease/No effect on IOP:

Ketamine

special consideration

Answer 19

may or may not

but DOES cause rotary nystamgus and blepharospasm and should be avoided during eye surgery

Question 20

why should ketamine be avoided during eye surgery

Answer 20

rotary nystagmus and blepharospasm

Question 21

T/f: the increase in IOP seen with sux can be blocked by a defasciculating dose of NDMR

Answer 21

false - unreliable

Question 22

Match drug with effect on aqeous humor:

Acetazolamide, echothiopate , Timolol

-decreases aqueous humor production, promotes aqueous humor drainage

Answer 22

Acetazolamide - decreases production (by inhibiting carbonic anhydrase)

Timolol- decreases production

Echothiopate - promotes drainage (via canal of schlmm)

echothiopate can prolong duration of sux and ester-type locals

Question 23

SF6 bubble

D/C nitrous when
avoid for how long after

Answer 23

D/c 15 mins prior
avoid 7-10 days after

Question 24

how long to avoid nitrous after silicone oil placed

air bubble?

perfluropropane (C3F8)

Answer 24

0 days

5 days

30 days

Question 25

2 key considerations for strabismus surgery?

Answer 25

PONV and occulocardiac reflex

Question 26

T/F: closed angle glaucoma is caused by closure of the posterior chamber

Answer 26

false - anterior chamber

just think- posterior chamber has the ciliary process (CP/PC) which produces aqueous humor - if that was closed, no aqueous humor would be produced and there would be a decrease in IOP

-anterior chamber has ashley shlemm canal which drains aqueous humor - if thats closed, it builds up and increases IOP

Question 27

T/F: open angle glaucoma is caused by the closure of the anterior chamber

Answer 27

false- closed angle

open angle is caused by sclerosis of hte trabecular meshmork, which impairs drainage of aqueous humor

Question 28

Why could a retrobulbar block result in apnea?

how long before you see it?

what should you assess that would provide an early indication that post-retrobulbar block apnea syndrome is about to happen?

Answer 28

bc injecting LA into the optic sheath is like giving a spinal block in the eye
if the LA reaches the brainstem, it can cause apnea

2-5 mins post injection; usually lasts 15-20 mins but full recovery 1hr

assess the contralateral pupil prior to doing the block
if the pupil starts small and dilates shortly after the block - be prepared to provide cardiopulmonary support auntil the LA is cleared from the CSF