Apex- misc: eyeballs Flashcards
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
D.
Intraoccular perfusion pressure = MAP - IOP
Aqueous humor is PRODUCED by the ciliary process (reabsorbed in the canal of Schlemn)
HYPERCARBIA increaes IOP
Normal IOP
10-20mmHg
T/F: increased IOP in a patient with an open globe injury can cause permanent blindness
True
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?
True
5-15mmHg for up to 10 mins
Roc 1.2mg/kg
What does a chornically elevated IOP that leads to retinal artery compression cause?
Glaucoma
IOP is reduced by drugs that do one of two things:
- reduce aqueous humor production (ciliary)
- facilitate aqueous humor drainage
What kind of surgery corrects the misalignment of the extraocular muscles and re-establishes the visual axis?
2 unique anesthetic considerations for this procedure
Strabismus surgery
PONV and oculocardiac reflex
Nitrous is contraindicated for how long after SF6 bubble placement?
when it that bubble be used?
7-10 days after
it’s placed over the retina during retinal reattachment, vitrectomy, and macular hole repair
Aterial supply to the eye
venous supply from the eye
ICA > Opthalmic Artery > Central Retinal artery & Posterior cilliary arteries
Opthalmic veins > cavernous sinus
Intraocular perfusion pressure =
Map - IOP
10-20mmHg = normal IOP
Aqueous humor is produced by what (where)
Aqueous humor is reabsorbed by what (where)
Produced by the ciliary process (posterior chamber) (CP/PC)
Reabsorbed by the canal of Schlemm (Anterior Chamber) (anterior - a, ashley schlemm)
Increase/Decrease/No effect on IOP:
Volatile anesthetics
Decrease
(decrease CVP/MAP)
Increase/Decrease/No effect on IOP:
Nitrous oxide
decrease - unless in combination with SF6 bubble, than increase
Increase/Decrease/No effect on IOP:
Hypothermia
decrease
Increase/Decrease/No effect on IOP:
NDMRs
decrease
Increase/Decrease/No effect on IOP:
propofol
decrease
Increase/Decrease/No effect on IOP:
Anticholinergics
No effect
Increase/Decrease/No effect on IOP:
LMA placement/removal
minimal effect
Increase/Decrease/No effect on IOP:
Ketamine
special consideration
may or may not
but DOES cause rotary nystamgus and blepharospasm and should be avoided during eye surgery
why should ketamine be avoided during eye surgery
rotary nystagmus and blepharospasm
T/f: the increase in IOP seen with sux can be blocked by a defasciculating dose of NDMR
false - unreliable
Match drug with effect on aqeous humor:
Acetazolamide, echothiopate , Timolol
-decreases aqueous humor production, promotes aqueous humor drainage
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
SF6 bubble
D/C nitrous when
avoid for how long after
D/c 15 mins prior
avoid 7-10 days after
how long to avoid nitrous after silicone oil placed
air bubble?
perfluropropane (C3F8)
0 days
5 days
30 days
2 key considerations for strabismus surgery?
PONV and occulocardiac reflex
T/F: closed angle glaucoma is caused by closure of the posterior chamber
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
T/F: open angle glaucoma is caused by the closure of the anterior chamber
false- closed angle
open angle is caused by sclerosis of hte trabecular meshmork, which impairs drainage of aqueous humor
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?
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
