Anesthesia for Opthalmic Surgery Flashcards
What nerves does a retrobulbar block inhibit?
CN 2, CN 3, CN 4, CN 5, CN 6
What is the only muscle missed when doing a retrobulbar block?
Superior Oblique muscle
This is seen in the isolated 4th nerve function
What nerve must also be blocked to ensure total anesthesia for eye surgery when doing a retrobulbar block?
CN 7 (this nerve is what allows you to squint your eye)
What in the eyeball acts as a shock absorber and protectant of the eye?
Orbital fat
How many “pops” do you feel when placing needle for retrobulbar block?
2
What are the two pops of a retrobulbar block with the needle?
: piercing of skin
: Piercing orbital septum
When your patient becomes unconscious and stops breathing approx 5-7 min after placing a retrobulbar block, what has occurred?
Subarachnoid brainstem anesthetic
What has occurred when a subarachnoid brainstem anesthetic presents?
Local anesthetic has entered the subarachnoid space and entered CSF
Where does the LA enter the CSF (how is it able to enter CSF) during a retrobulbar block?
At the spatium intervaginale. Is entrance of optic nerve at back of eyeball that brings a sheath of dura into eyeball thus allowing direct pathway to CSF
What are the muscles of the eyeball?
talk about right eye
Lateral side: Lateral rectus Bottom: Inferior rectus Top: Superior Rectus Medial: Rectus medialis Obliques: Superior and Inferior obliques
Presbyopia tends to start to onset during what stage in life?
5th decade
What is presbyopia?
When the cillary body tenses but lens does not follow suit and flatten out, causing lack of near sightedness
Where is the aqueous humor of the eye made?
Cillary bodies
How many chambers are there in the human eye, and what separates them?
2 chambers , Posterior and anterior
Separated by Iris
What is the plastic like bag that is filled with jello?
Lens
When the cillary bodies relax, which part of eyesight is seen?
Far sight
When the cillary bodies tense, what eyesight is seen?
Near sight
What is known as an increase in intraocular and is treated when pressure becomes greater than 25 mmHg?
Glaucoma
What is one the leading causes of cataract?
Diabetes
What is cataract?
Clouding of the lens of the eye that results in vision being distorted
What dilating drops are used in opthalmic surgery?
10% phenylephrine
What is the concentration of 1 drop of 10% phenylephrine?
7mg
Systemic absorption of opthalmic drops occurs through what mechanism?
Through the tear duct system and drainage into/through nose (which is highly vascular)
What are 3 determinants for intraocular pressure?
- Extrinsic pressure
- Scleral rigidity
- Alteration of eye contents
What happens when pressure rises in the eye high enough to cause bleeding into eye that displaces the retina?
Expulsive hemorrhage
Expulsive hemorrhage causes loss of vision and loss of eyeball, what are some causes of this?
- Coughing on tube
- Bucking on tube
What are the most important determinants of intraocular pressure?
Rate of formation and drainage
What are some things that increase intraocular pressure?
- Acute hypertension
- Hypoxia
- Succinylcholine
What are some things that decrease intraocular pressure?
- Inhalation anesthetics
- Non depolarizing NM blockers
What controls the afferent signal of the oculocardiac reflex?
Trigeminal nerve
What controls the efferent signal of the oculocardiac reflex?
Vagus
The oculocardiac reflex is seen most on which extra ocular muscle?
Medial rectus
What are some causes of oculocardiac reflex?
- Pressure on the globe
- Ocular trauma
- Traction on Extra ocular muscles
What is the main bad outcome of the oculocardiac reflex?
Bradycardia
Cataracts can be done by which type of anesthesia?
Local or general anesthesia
What is one main concern from cataract surgery?
Expulsive hemorrhage
When doing strabismus surgery, what drug do you have to stay away from?
Succinylcholine
What is at very high risk when performing strabismus surgery?
M-H susceptible patients
During strabismus surgery, an oculo-gastric reflex sometimes occurs, what is this?
Vagal mediated onset of PONV that cannot be fixed/cured by drugs
When doing a glaucoma patient, what is the most important parameter to control?
Strict control of intraocular pressure
Is there a risk of having eye surgery if your patient has had a prior MI?
NO risk at all
During a retinal detachment surgery, what gas is used to press retina against the outer wall of the eye?
Sodium Hexaflouride
Eye injuries represent how much percent of the ASA closed claims database?
3%
Of the eye injuries reported, what was the most common injury?
Corneal abrasion
Are corneal abrasion injuries permanent?
NO
What is the second leading cause of eye injuries but is the most detrimental to patient safety?
Patient movement
always results in blindness
Does patient movement have a higher incidence during general surgery or MAC cases?
General surgery
So when doing general anesthesia for eye surgery, the patient should be deeply anesthetized and paralyzed , T OR F?
TRUE
Who is the father of Local Anesthetics?
Carl Kholar
What did Kholar first use as LA on patients?
Cocaine
What was Dr. Morrow’s choice of LA?
4 mL of 0.75% marcaine
4 mL of 2% Lidocaine
1 mL of Hyaluronidase 200 units/mL
What is the best needle to use for eye blocks?
Single bevel needle that is flat ground
Why are eye block needle flat ground?
To feel tactile sensation needed to be precise
What are eye block needles called?
Atkinson needles
FLGR
What block is similar to a spinal because of its low volume and rapid onset?
Retrobulbar block
What are some disadvantages of a retrobulbar block?
- -Hematoma
- -Brainstem anesthetic
- -Perforation of globe
- -Oculocardiac reflex
Explain how to place a needle for retrobulbar block.
- SOMEONE INSERT NAME OF LOCATION WHERE NEEDLE GOES
- Feel skin pop, feel orbital setpum pop
- Tilt needle inferior, advance catheter further
- Place 4 mL of LA at back of orbit
- Place 1 mL of LA on way out
The facial nerve block that occurs near the first division of the facial nerve near the tragus and TMJ
Nadbath
The facial nerve block that occurs near the superior portion of the eye (supra orbital)?
Van Lint
Which eye block is similar to an epidural because takes large volumes, longer onset of action, and requires frequent supplementation?
Peribulbar block
What are the advantages to a peribulbar block?
- Avoids injection into muscle cone
- Avoids need for facial nerve block
- Lowers risk of globe perforation
Explain how to do the peribulbar block?
- 1 injection on top part of eye and 1 injection of bottom side of eye, on either side of the midline
- Walk the wall of the orbit until reaching adequate depth
- Inject 4 mL on top
- Inject 4 mL on bottom
How long must you wait to check for peribulbar blocks to take effect?
10 min
What must you use for 20 min after placing a peribulbar block?
Ocular compression device to prevent increases in intraocular pressure
What are the 2 main indications for a peribulbar block/
- Long axial eye length
- - Previous extra-ocular surgery
What is a normal axial eye length?
20-22 mm
A high myope has what characteristics?
- Very nearsighted
- Long axial length
- requires spherical correction of < -5.00 D
What is the maximum axial length that you can perform a retrobulbar block?
26 mm
Anything longer requires peribulbar block
The first set of numbers when reading a ophthalmologist diagnosis states what?
Spherical correction
- Positive numbers corrects far sightedness
- Negative numbers corrects near sightedness
The second set of numbers when reading a ophthalmologist diagnosis states what?
Cylindrical corrections
– Corrects for stigmatism’s
The last number when reading a ophthalmologist diagnosis states what?
Bifocal corrections
– Correct up close vision
