1
Q
- What is the oculocardiac reflex (what reflex arc is it)?
- what causes it?
- What does it cause?
- who usually gets it?
- what preventable condition potentiates or worsens it?
A
- trigeminal vagal reflex arc
- stimulated by traction on extraoccular muscles (especially medial rectus, as well as conjunctiva and other orbital structures) or pressure on the globe.
- usually causes bradycardia, junctional, av block.
- common in pediatric patients undergoing strabismus surgery
- hypoxia or hypercarbia increase severity.
2
Q
- how is oculocardiac reflex treated?
2. what preventative measure can be taken?
A
- local to eye muscle
- atropine 3-6 mcg/kg (4 mcg/kg in pediatrics)
- will eventually fatigue itself
- anesthetic injected (via infiltration) to medial rectus muscles by MD
2. prophylactic atropine as part of pre op meds
3
Q
what should you draw up when doing eye cases?
A
atropine
4
Q
what are patient conditions cause problems in eye surgery when trying to sedate.
A
- persons with chronic cough
- persons with orthopnea
- claustrophobia
- persons with tremors (parkinsons)
5
Q
- How is a retrobulbar block done?
- what is used to spread the effect of the block?
- what are signs of a successful block?
A
- lido or bupiv is injected into muscle cone of extraocular muscles, followed by injection into facial nerve
- hyaluronidase (a connective tissue polysaccharide hydrolizer which breaks down tissue)
- eye akinesia, abolishment of oculocephalic reflex
6
Q
what can sedation cause that you dont want?
A
older patients to get restless, topical is usually the best
7
Q
what should you do during eye surgery under general?
A
if general, keep patient sedated, paralyzed and deep
8
Q
- What is detatched retina
2. Who gets them & why?
A
the retina pulls away from inner wall of eye, sometimes happens to older persons as vitrious humor shrinks
9
Q
repair of detatched retina:
A
- injection of gas bubble (air or sulfur hexaflouride (sf6)) to hold sclera down, the air is eventually reabsorbed.
- Scleral buckle
10
Q
- what gas would you not want to use in patients receiving gas bubble for detatched retina
- how long should someone wait before having this gas again?
A
- no nitrous oxide for 10 days
11
Q
if you attempt to intubate and you fail, make sure that you document what?
A
document 0 of 4 on TOF , so that it is known that the patient was fully paralyzed
12
Q
what kind of risk might a child with strabissmus have during and after surgery?
A
increased risk of malignant hyperthermia
high incidence of ponv
high incidence of oculocardiac reflex
13
Q
sclera
- what is it?
- describe it?
- what is its job
A
- continuous with cornea at corneoscleral jujction, posterior sclera is preforated by optic nerve
- smooth and white, separated from blulbar fascia by loose connective tissue
- protect eye, retain shape of eye
14
Q
cornea
A
transparent centor portion of sclera that permits light into ocular structures
15
Q
uveal tract
A
aka middle layer
vascular; direct opposition of sclera
16
Q
What is the suprachoroidal space?
A
a potential space that separates the sclera from the uveal tract; it can become filled with blood when injured
17
Q
iris
- what is it?
- what does sympathetic innervation do to it?
- what does parasympathetic?
A
- includes the pupil; 3 sets of muscles that contract to control light entering eye
- sympathetic- controls iris dilator muscle (dilates/midriasis)
- parasympathetic- controls iris sphincter & cilliary muscle (constricts/miosis)
18
Q
cilliary body
- what is it/ what does it do?
- what is the innervation type & from what cranial nerve?
A
- contains cilliary body which adjust the shape of the lens to accomodate focusing at various distances
- muscles innervated by parasympathetic fibers of occulomotor nerve
19
Q
choroid
what is it?
A
contains vessels and capillaries (choriocapillaris) which supply nutrition to outer part of retina
20
Q
retina
- what is it?
- what spinal nerve innervates it?
A
- neuro-sensory membrane composed of 10 layers which convert light impulses into neural impulses
- optic nerve
21
Q
vitreous humor (VH)
- what is it?
- where is it?
- what can it cause?
A
- gelatinous (viscous=vitreous) substance adherent to the anterior most 3 mm of the retina as well as to large blood vessels and optic nerve
- located in center of globe
- may pull at retina causing retinal tears and detachment
22
Q
aqueous humor (AH)
- what is it?
- what is its function?
A
- cear (thinner) fluid produced by cilliary body of posterior chamber
- provides essential metabollic materials and removes waste via Canal of Schlemm (outflow)
23
Q
what is normal IOP (intra ocular pressure)?
A
10-20 mmHg
24
Q
what is the physiological cause of increased IOP?
A
increase in venous pressure -OR-
decrease in the cross-sectional area of the eye
-which causes a resistance to outflow (which causes increased IOP)
25
1. what disease causes increased IOP?
| 2. How?
1. glaucoma
| 2. causes an obstruction of aqueous humor outflow
26
1. what does decreasing the size of the globe without decreasing the pressure in the globe cause ("squeezing the balloon")?
2. what other situations can cause this "squeeze"
1. increased IOP
| 2. imroper prone positioning, mask pressure, retrobulbar hemorrhage
27
1. osmotically speaking, what infulences the formation of aqueous humor?
2. If COP goes up, what happens to IOP?
1. the osmotic pressure difference between aqueous humor and blood plasma (Osmotic pressure of AH is > plasma)
2. increased COP = decreased IOP
28
intraocular blood volume
1. what determines it?
2. what does a rise in venous pressure do to IOP?
1. detremined by vessel dilation or contraction (in spongly layers of choroid).
2. increased IOP by decreasing AH drainage and increasing choroidal blood volume
29
1. what do we do to patients (or they do themselves) that will increase IOP?
2. by how much does the IOP change?
3. what could this lead to?
1. things that increase IOP: laryngoscopy, intubation, trendelenberg, airway obstruction, coughing, straining, vomiting, Valsalva, increased venous pressure
2. to up to 40 mmHg
3. permanent damage
30
1. what percent of eye injury claims associated with anesthesia were from patient movement?
2. what was the outcome (eye damage)?
1. 30%
| 2. blindness
31
pre op assessment of eye patients:
1. characteristics of patient population?
2. what diseases are usually prevelant?
3. what should the CRNA check for in pre op assessment?
1. mostly very old or very young
2. cardiovascular disease, diabetes, copd
3. check all medications (know what they are), check routine labs, ekg, check for claustrophobia, orthopnea, tremors, chronic coughs (all could cause movement during procedure or be difficult to manage sedation with).
32
step by step retrobulbar technique
1. ?
2. ?
3. ?
4. ?
1. blunt tipped 25g needle with 2-5cc local anesthetic is used to penetrate lower lid at junction of middle and lateral one third of orbit (0.5 cm medial to lateral canthus)
2. have patient stare supranasally as the needle is advanced 3.5 cm toward the apex of the muscle cone
3. aspirate
4. inject the LA
33
1. what is a peri-bulbar block?
| 2. what is it supplemented with (if necessary)?
1. a block injected outside of the muscle cone
| 2. can be supplemented with a small (3cc retrobulbar injection and lid block).
34
what monitors must be on a patient prior to a block?
1. ekg
2. pulse ox
3. BP
4. saO2
35
1. what meds can be given prior to a block?
| 2. what must one watch for (with meds)?
1. 30-60 mg IV brevital; propofol, remifentanyl, versed
| 2. watch for synergism with sedatives and narcotics
36
complications with eye surgery
1. odds?
2 time frame of occurence?
3. what are the potential complications (11 of them)
1. 1 in 500
2. within 15 minutes
3. retrobulbar hemorrhage, preforated globe, optic nerve atrophy, convulsions, occucardiac reflex, respiratory issues, cardiac arrest, hypotension, bradycardia, diaphoresis, nausea.
37
treatment for occular surgery complications
osygen, trendelenberg, crystaloid, iv atropine
38
1. what is post retrobulbar apnea syndrome?
2. what are initial and later s/s?
3. how long does it last?
1. caused by injection of LA into optic nerve sheath with spread into CSF.
2. initial: apprehension, then unconsciousness
- apnea within 20 minutes
3. one hour
39
contraindications to eye surgery (6 of them)
1. coagulopathies
2. open eye injury
3. chronic cough
4. claustrophobia
5. orthopnea
6. refusal of local anesthetic
40
maintainance of anesthesia during retrobulbar block:
| 6 things
1. all routine monitors including precordial (ALWAYS)
2. two iv extensions on IV
3. dont give too much sedation (patient may become confused and uncoopertive)
4. O2 via nasal canula
5. communicate frequently with patient either tactile or verbally (first signs of LA going IV is change in behavior or LOC)
6. if GA, tape all connections and keep patient deep & paralyzed
7. watch sedation, electrocautery and o2
8. antiemetic especially with narcotics (stimulate CRTZ)
41
1. how is emergence performed on eye surgery?
2. why deep extubation?
3. head of bed position?
1. deep extubation if GA (and if NPO-which they should be)
2. to avoid cough or things that increase IOP
3. HOB up
42
```
common opthalmic procedures:
cataract extraction:
1. what is it?
2. how is it done
3. how is it visualized; anesthetized?
4. what are the doses of the anesthesia?
5. what anesthesia technique?
6. who usually has cataract surgery?
```
1. lens is removed and replaced with a plastic one.
2. lens is removed by emulsifying it and suctioning it off eye
3. ultrasound technique done under local anesthesia (drops)
4. 5% tetracaine, 1% ropivacaine, 1% lidocaine
5. done under sedation
6. usually elderly; hx of cardiac disease, chronic lung disease, arthritis, senility
43
```
opthalmic procedures:
Trabeculectomy:
1. what is it?
2. how is it done
3. who gets this procedure?
```
1. a procedure to lower intraocular pressure in patients with glacoma.
2. a fistula is created form the anterior chamber to the subconjunctival space
3. pediatric patients and adults
44
Detatched retina:
1. what is it?
2. what causes it?
1. If the retina separates form the inner eye wall, it will not function and vision will be lost.
2. the vitreous humor shrinks with age and can pull away from the rentin. usually without a problem. in some cases, the pulling away from the retina causes rips in the retina in which the vitreous humor can leak into causing further separation.
45
what 2 ways are a detatched retina repaired
1. gas bubble
| 2. scleral buckle
46
1. what is the gas bubble technique?
2. what happens to the bubble?
3. what is another gas bubble (chemical) & how long does it last?
4. what happens if this person gets nitrous?
1. a smal gas bubble is injected into the vitreal cavity to hold the retina in place so it can heal
2. in 5 days the bubble will be absorbed by gradual diffusion.
3. sulfur hexafluride (SF6) is inert and less soluble, lasts 10 days, does expand but is very gradual so that it doesnt raise IOP.
4. if given nitrous, it will enter the eye and expand (70% triples in size in 30 minutes), this would increase IOP. Once discontinued, the nitrous would rapidly leave the eye causing the retina to re-detatch.
47
how long should a person who gets gas bubble technique for detatched retina repair wait before receiving nitrous?
10 days
48
vitrectomy; what is it?
removal of vitreous fluid with replacement with synthetic vitreous material
49
strabismus surgery:
1. what is it?
2. what patient population has it done?
3. what type of anesthesia is this done under?
4. what test is done to determine surgical plan for strabismus
1. involves shortening individual muscles or pairs of muscles to cosmetically straighten out eyes and allow for binocular vision
2. mostly on children especially cerebral palsy children; also meningimyelocele with hydrocephalus and seen in patients that suffer from malignant hyperthermia
3. general anesthesia
4. Forced Fuction Test
50
open eye injury:
1. what is it?
2. what is the goal in care?
3. what else should you consider? what is the caveat to that?
1. ruptured globe
2. avoid even minimal increases in intra occular pressure which would cause hemorrhage and loss of vitreous humor
3. consider possiblity of full stomach (since usually a trauma); may require RSI, HOWEVER, succ raises IOP (weigh the pros and cons).
51
induction of eye injury patient:
1. what medication is controversial?
2. what medications are safe?
3. what is the best RSI method?
4. give meds and doses for RSI
1. succ
2. non depolarizing MRs, sodium pentothal
3. using non depolarizing MRs and cricoid pressure
4. a) lidocaine 1.5 mg/kg
b) fentanyl 2-3 mcg/kg
c) propofol 2 mcg/kd
d) rocuronium 0.6-1.2 mg/kg
52
1. what can incomplete relaxation cause (the reason why your TOF should be 0 /4)
2. what can be used prior to intubation to prevent coughing?
1. causes coughing and other inadequate intubating conditions
2. lidocaine LTA
53
what other meds are good when intubating eye patients
LTA
54
how deep should maintainance be
deep enough to prevent cough or movement
55
1. emergence of eye patient should be?... what does this prevent?
2. what other medications should you give to prevent post op increased IOP (& for what reason)
1. should be smooth, deep extubation is best to prevent increased IOP with coughing, bucking
2. antiemetic (dramamine preop, decadron zofran) Post op vomiting and wretching will increase IOP
56
1. what type of extubation for rapid sequence with eye surgery?
2. what can you give IV minutes before extubation?
1. awake and reflexive (but not wide awake), HOB elevated,
| 2. lidocaine 1.5 mg
57
what does eye surgery require as far as eye muscles go?
relaxation of the recti muscles (akinesis)
deep anesthesia is required
NDMR or retrobulbar block
58
what do children require for opthalmic procedures?
general anesthesia
59
patients with strabismus are at risk for
1. malignant hyperthermia
2. 50% risk of ponv
3. high incidence of oculocardiac reflex
60
why is there a fire risk?
with the use of oxygen and electrocautery
b. princip. exam 2 (w13)
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