Week 1 Anesthesia for Eye Surgery Flashcards
The eye resides in the _________ bony structure.
pyramidal
What are the three layers of the eye?
- Sclera
- Uveal tract (middle layer)
- Retina
Where does the eye get most of its focusing power?
Curvature of the cornea
Name the three layers of the uveal tract (middle layer)?
- Choroid
- Ciliary body
- Iris
What are the features of the choroid layer in the eye? (Uveal layer)
- Layer of blood vessels
- Located posterior
What are the features of the ciliary body of the eye? (Uveal Layer)
- Resides behind the iris
- produces the aqueous humor
- adjust the focus on the lens by reducing the tension on suspension fibers or zonules of the lens
What are the feature of the Iris? (Uveal layer)
- Pigmented
- Controls the light entry
What occurs within the iris during sympathetic response in the eye?
-Iris DILATOR muscle contracts
dilitation or MYDRIASIS
What occurs within the iris during a parasympathetic response in the eye?
-iris SPINCTER muscles contracts
pupillary constriction or MYIOSIS
The retina ends __ mm behind the iris.
4
Where is the Pars plana located?
-Area between limbus (edge) of cornea and end of retina
T/F: The Pars plana is the safe entry point for vitectomy procedures?
TRUE
How does ocular cardiac reflex (OCR) manifest?
- bradycardia
- AV block
- ventricular ectopy
- asystole (rarely)
Ocular cardiac reflex is seen especially with traction on this muscle?
Medial rectus
What nerve is primarily responsible for the ocular cardiac reflex?
-Trigeminovagal
T/F: The ocular cardiac reflex will improve with hypoxemia and hypercarbia.
FALSE
How would ocular cardiac reflex be treated?
- Ask surgeon to stop
- Assess ventilation
- Lidocaine localization or deepen anesthetic
- Atropine
T/F: Ocular cardiac response fatigues with repeated stimulation.
TRUE
What regulate the intraocular pressure (IOP)?
- aqueous fluid
- blood volume
What is normal intraocular pressure (IOP)?
10 to 22 mmHg
If intraocular pressure rises above __ mmHg it is considered _______.
> 22
-pathological
Aqueous fluid production is constant and facilitated by _________.
carbonic anhydrase
Increase intraocular pressure leads to ocular HTN and structural changes causing?
- atrophy of optic disc
- atrophy of nerve fibers
- optic artery occlusion
Decreased intraocular pressure leads to:
-fluid accumulation in the eye
An increase to CVP increases intraocular pressure more than the increase of ___________.
blood pressure
How much could coughing increase intraocular pressure?
40 mmHg
What will occur to intraocular pressure if PaCO2 drops suddenly?
-FAST drop in IOP due to choroidial vasoconstriction
What will occur to intraocular pressure if PaCO2 increases?
-SLOW increase in IOP
Metabolic acidosis _______ the choroid vessel volume and therefore IOP.
Decreases
Metabolic alkalosis ________ the choroid volume and the IOP.
increases
What will most anesthetic drugs do to the IOP.
Decrease the IOP
What two anesthetic drugs would be avoided if elevated IOP was a concern
- Etomidate
- Ketamine
Non depolarizing NMR do not alter IOP with exception of curare which ______ it.
decrease
Azetazolamide (Diamox) is used to ________ aqueous production by carbonic anhydrase inhibitor.
Decrease
Osmotic diuretic will ______ IOP and will have a max effect at 30 to 45 minutes and return to normal after ____.
- decrease
- 5-6 hours
Echothipate opth. is used to treat glaucoma and is a ___________ drug. This could prolong muscle paralysis after __________.
- anticholinesterase
- succinylcholine
Flomax ( Tamsulosin) is selective alpha antagonistic. It binds to the dilator muscle causing dilation and complicates cataract surgery. This could last for up to ______ off therapy.
7 - 28 days
Facial nerve block causes what block to the eye muscle?
orbicular oculi muscle
What are the three facial nerve blocks?
- Van Lint.
- Atkinson
- O’Brian
What is the major complication of a facial nerve block?
subcutaneous hemorrhage
What will the Nadbath Rehman block and effect.
BLOCK
-Entire tunk of facial nerve
EFFECT
- lower facial droop postop for several hour
- vocal cord paralysis,laryngospasm, dysphasia and respiratory distress (close to the vagus and glossopharyngeal nerve)
What muscle may not be blocked by a retrobulbar block?
-Superior rectus muscle
Retrobulbar hemorrhage is the most common complication of the block and observation of _____ must be monitored.
ocular cardiac reflex (OCR)
Injection of the block in the optic sheath could cause what complications?
- contralateral amaurosis (lack of vision)
- obtundation
- respiratory arrest (within 20 minute and last for up to an hour)
- vascular collapse form depressant effect on the medulla (total spinal)
If sulfur hexaflouride is used as an air bubble in eye surgery then N2O should be d/c’d __ minutes before placement of bubble and avoided ______ days after surgery.
- 15
- 7 to 15
If Perfluoropropane is used as the air bubble in eye surgery then avoid N2O for up to ___ month after instillation.
1
Ketamine in eye surgery is usually avoided due to __________.
nystagmus
