Eye Anesthesia - Exam 5 Flashcards
What are the requirements of Ophthalmic surgery?
Safety
Akinesia
Analgesia
Minimal Bleeding
Avoidance or obtundation of oculaocardic reflex
Control of intraocular pressure
Awareness of drug interactions
Smooth emergence
3 layers of the wall of the globe
- sclera = outermost layer
- uveal tract = middle layer
- retina = inner layer
Characteristics of the sclera
-tough, fibrous
-the white part
-continuous with cornea anteriorly
The place where the cornea and sclera meet is called
limbus
____% of focus power cones from curvature of cornea
60%
Uveal tract: 3 structures
- choroid
- iris
- ciliary body
What is the main blood supply to the eye? What does it divide into?
Ophthalmic artery
Central retinal artery
Posterior ciliary artery
How are ocular surgeries classified and why is this important?
Extraocular or intraocular.
Anesthetic considerations are different for each category
What is the choroid
large layer of blood vessels located posteriorly
The _____ is the pigmented portion of the eye that controls light entry with muscle fibers that change size of pupil
iris
SNS stimulation causes pupillary ______
PNS stimulation causes pupillary ______
dilation
constriction (meiosis)
What do ciliary bodies do
produce aqueous humor
What is uveitis
Inflammation of the uveal tract (iris, ciliary body, choroid)
ending in itis - inflammation
What is the retina
highly specialized nerve tissue that is consistent with optic nerve
T/F the retina gets oxygen and nourishment from its dense capillary network
FALSE
choroid plexus supplies blood, no capillaries in retina
Why is retinal detachment bad
it detaches from choroid plexus (which supplies all its blood) so it becomes ischemic and is a major cause of vision loss
T/F the pars plana is a safe entrance site for vitrectomy procedures
TRUE
Center of the eye is filled with ______
vitreous fluid
What is the function of the superior and inferior ophthalmic veins?
Transport venous blood to the cavernous sinus
What is the equation for intraocular perfusion pressure?
MAP - IOP
Normal range for IOP
10-21.7mmHg
Because the globe is relatively noncompliant, what factors determine IOP?
Choroidal blood volume, aqueous fluid volume, and extraocular muscle tone
What is the aqueous humor and why is it important to ocular surgery?
A clear watery fluid that fills the space between the cornea and the lens.
The formation and drainage of the aqueous humor influence IOP.
Where is the aqueous humor produce and where is it reabsorbed?
Produced by the ciliary process in the posterior chamber
Reabsorbed by the canal of Schlemm in the anterior chamber
Cause of retinal detachment
traction of the vitreous on the retina
Layers of the eyelid
skin, muscle, tarsal plate of cartilage, conjunctiva
Lacrimal gland sits where
superior temporal orbit
CN that move the eye
3,4,6
oculomotor, trochlear, abducens
Local anesthetic block of the ciliary ganglion produces a ________ pupil
fixed and mid-dilated
What occurs when the oculocardiac reflex (trigeminovagal reflex) is triggered?
traction on extraocular muscles or pressure on globe causes bradycardia, AV block, ventricular ectopy, or asystole
T/F oculocardiac reflex is fairly common
TRUE
T/F the oculocardiac reflex fatigues with repeated stimulation
TRUE
oculocardiac reflex seen most often with traction on which muscle, which population, and which surgery
medial rectus (extraocular muscle)
children
strabismus surgery (medial rectus muscle)
Afferent vs efferent branch of oculocardiac reflex
afferent = orbital contents -> ciliary ganglion -> ophthalmic division (V1) of trigeminal n
efferent = vagus nerve to heart
T/F retrobulbar block is effective at preventing oculocardiac reflex
FALSE
not always.
Stimuli for oculocardiac reflex
-traction to extra ocular muscles (medius rectus)
-strabismus surgery (children)
-pressure on globe or conjunctiva
-ocular manipulation or pain
-ocular injection (blocks)
-retrobulbar block
-manipulation after orbital enucleation
-ocular trauma
First step if pt experiences oculocardiac reflex
tell surgeon to stop manipulation
then make sure they are deep enough, give atropine
Dose of atropine for oculocardiac reflex
0.02mg/kg increments
If atropine and deepening sedation don’t work, what can we ask surgeon to do during oculocardiac reflex
infiltrate medius rectus muscle with some local anesthetic
Things that will exacerbate oculocardiac reflex
hypoxia, hypercapnia, acidosis, inadequate depth of anesthesia
*key concept/testable
What are the 2 factors that regulate* IOP?
- volume of aqueous humor
- volume of blood in choroid plexus
3 Main factors that influence IOP
External pressure on the eye
Scleral rigidity
Changes in intraocular contents that are semisolid (lens, vitreous, or intraocular tumor) or fluid (blood and aqueous humor)
Major control of intraocular tension is exerted by
the fluid content (aqueous humor)
T/F increases in choroidal blood volume cause slow increases in IOP
FALSE
very quick increase in IOP
What increases IOP?
Hypercarbia
hypoxemia
increased CVP
increased MAP
Laryngoscopy/intubation
Straining/coughing
Succinylcholine
N2O (if SF bubble in place)
Trandelenburg position
Prone
External compression by facemask
What decreases IOP?
Hypocarbia
decreased cvp
decreased MAP
volatile anesthetics
N2O
Nondepolarizing NMB
Propofol
Opioids
Benzos
Hypothermia
True or false: Anticholinergics do not increase IOP
True
True or false LMA placement/removal has significant effect on IOP
False, minimal
Ketamine should be avoided in eye surgery, but not because of IOP effects. Why is it contraindicated?
It causes rotary nystagmus and blepharospasm
What can cause dysrhythmias during eye surgery?
-traction on extraocular muscles
-pressure on globe
-ocular manipulation
-ocular pain
=bradycardia, AV blk, vent ectopy, asystole
What is A?
vitreous body
-fills globe centrally with vitreous humor
What is B?
Lens
-REFRACTS rays of light passing thru cornea and pupil to FOCUS image onto retina
What is C?
Cornea
-highly vascular and transparent, PERMITS light passing
What is D?
**Pupil
-part of the iris, CONTROLS AMOUNT of light entering eye
What is E?
**Iris
-colored part containing dilator and sphincter muscle fibers controlling CENTRAL APERTURE
What is F?
Sclera
-fibrous, white OUTER LAYER, protective and MAINTAINS EYE SHAPE
this is tricky with the retina being so close, be careful
What is G?
Optic n
-SENDS electrical signals to brain to make images
What is H?
Retina
-posterior aspect of eye, CONVERTS light into electrical signals
this is tricky with the sclera being so close, be careful
Volume of each orbit:
~30mL
Average globe diameter:
23.5mm ~1in
Which bones are part of the orbit?
-frontal
-zygomatic
-greater wing of sphenoid
-maxilla
-palatine
-lacrimal
-ethmoid
What transmits the optic nerve and ophthalmic artery? What about everything else?
optic foramen
superior orbital fissure
3 layers of eye:
Sclera
Uveal Tract (contains Iris, Ciliary body, and Choroid)
Retina
What part of eye absorbs drugs?
conjunctiva!
-also is the pink part of pink eye!
The iris DILATOR muscles are _ innervated by the ophthalmic division of CN _, which dilates the _.
sympathetically
CN V
pupil
The iris SPHINCTER and ciliary muscles are innervated by the _ nervous system via CN _, causing pupil constriction or _
parasympathetic
CN III
miosis
Posterior to the iris is the _ _ which produces _ _
ciliary BODY
aqueous humor
Ciliary muscles adjust the shape of the _ to accommodate _ at various distances
lens
focus
The conjunctiva is where the tendons of _ muscles insert, and controls _ of light into the eye
rectus
refraction
What supplies nutrition to the outer part of the retina?
choriocapillaris (makes up choroid which is a network of small vessels and capillaries)
Parts of posterior segment of eye:
VITREOUS Humor, Retina
-neurosensory membrane, converts light into electric signals the optic n sends to brain
Macula
-oval, pigmented area in center of retina/central and high acuity vision
Root of optic N
Parts of anterior segment of eye:
2 chambers:
Anterior
behind cornea, filled with aqueous humor or vitreous humor
Posterior
Lens - refracts light thru cornea and pupil to focus image on the retina
**both chambers are separated by the iris and communicate via the pupil
6 extraocular muscles are made up of:
4 rectus muscles-delineate the retrobulbar cone
-superior, inferior, lateral, medial rectus
2 oblique muscles
-superior and inferior oblique
Explain the pyramidal shape of the orbit cavity.
apex = posterior part
base= anterior opening
How can a retinal detachment/tear occur?
vitreous humor can pull on the retina
-diabetic retinopathy= neovascularization of retina-> retinal detachment
What regulates thickness of lens?
ciliary muscle
Purpose of lacrimal gland:
-maintain moist anterior surface of globe, drains into nose below and can be blocked
What supplies blood to the eyE?
branches of internal and external carotid arteries
What drains blood from the eye?
anastomoses of superior and inferior ophthalmic veins, mainly the central retinal vein, draining blood into the cavernous sinus
Average rate of aqueous humor production:
2mcL/ min
Sensory innervation of orbit and globe:
Frontal and nasociliary branches of Ophthalmic nerve (1st branches CNV)
Infraorbital and maxillary nerve (2nd branch of CN V)
-part of floor of orbit
Optic Nerve (CN II)
-sends info from the retina
Motor innervation of orbit and globe:
**Trochlear (CN IV)
-superior olique m
Abducens (CN VI)
-lateral rectus m
Oculomotor (CN III)
-extraocular m
Branch of CN III
-motor root of ciliary ganglion-> sphincter of pupil and ciliary m**
Facial (CN VII)
-functions in blinking/closing eye
Superior rectus m
-innervation
-function
CN III
Elevation
Inferior Rectus m
-innervation
-function
CN III
Depression
Medial Rectus m
-innervation
-function
CN III
ADDuction
Inferior Oblique m
-innervation
-function
CN III
elevation, ABDuction, MEDIAL rotation (extorsion)
Superior Oblique m
-innervation
-function
CN IV
depression, ADDuction, EXTERNAL rotation (intorsion)
Lateral Rectus m
-innervation
-function
CN VI
ABDuction
Zygomatic branch of facial nerve (CN VII)
-upper branch innervates
frontalis m and upper lid
Zygomatic branch of facial nerve (CN VII)
-lower branch innervates
orbicularis m of lower lid
Which nerve supplies most of the muscles that MOVE the eye?
CN III Oculomotor
Which nerve provides a majority of sensory innervation to the orbit and globe?
Trigeminal nerve (CN V)
3 divisions:
V1: ophthalmic
V2: maxillary
V3: mandibular
Which nerve carries SENSORY information from the retina?
CN II Optic n
Aqueous Humor Flow
1. 2/3 is made in _ chamber, by the _ body.
2.This flows from the posterior chamber into the anterior chamber via the _ aperture
3. This mixes with the other 1/3 which is made by _ filtration from vessels on anterior surface of _.
4. Eventually flows to the venous system and into the _ _ _, then the _ atrium
5. An obstruction between the eye and _ atrium would then increase _ _ _.
- posterior, ciliary
- pupillary
- Passive, iris
- superior vena cava, right atrium
- right, intraocular pressure (IOP)
Normal IOP range
Abnormal IOP is:
Normal= 10-21.7 mmHg
Increased IOP = >22mmHg
Most important determination of IOP=
aqueous humor production/elimination
-also external pressure on eye and scleral rigidity
What reflex causes dysrhythmias during eye surgery? What are its 2 limbs?
Trigeminovagal Reflex AKA Oculocardiac Reflex
AFFerent= orbital contents, ciliary ganglion, ophthalmic division of CN V (floor of 4th ventricle)
EFFerent= Vagus n to heart(via visceral motor nucleus in reticular formation; decreases SA node output)
What WORSENS the trigeminal nerve reflex?
-hypoxia
-hypercarbia
-light anesthesia
acidosis
What triggers the oculocardiac/ trigeminovagal reflex?
-eye block (also lessens chance of it once blocked)
-ocular pain (postop)
-ocular trauma
-manipulating orbital apex
-ocular manipulation
-direct pressure on globe
-traction of extraocular m (esp medial rectus, but all can)
Treatment of oculacardiac/ trigeminovagal reflex:
-tell surgeon to stop manipulation - number one
-deepen anesthetic, support ventilation
-brady? -> atropine 0.02mg/kg ~1-2mg if brady significant, if mild -> glyco 0.2-0.4mg IV
-persistent brady? - > infiltrate rectus muscle with LA
-reflex will fatigue after a while
Increased IOP during anesthesia can cause:
permanent vision loss
Which 2 fluids regulate IOP?
-aqueous humor
-choroidal volume
What is a possible effect of local anesthetic injection to treat OCR?
act of injecting LA can cause reflex
When should glyco be used in OCR?
if pt is brady ~20% from baseline (HR drop from 70->50)
GIVE: 0.2-0.4mg IV
When should atropine be used in OCR?
if pt is severely brady or asystole
GIVE: 0.02mg/kg OR 1-2mg IV
Increasing already elevated IOP can cause:
glaucoma
Penetration of globe when IOP is high causes:
ruptured blood vessel -> hemorrhage
When is IOP higher, sleep or awakening, why?
awakening
-vascular congestion, pressure on globe from closed eyelids and dilated pupils
Sclerosis is associated with _ scleral compliance and _ IOP. (increases/decreased)
decreased
increased
T/F It is appropriate to pretreat all pts having eye surgery with atropine to avoid OCR.
False
-just kids (more common)
0.02mg/kg Atropine or 0.01mg/kg Glyco
Relevant neural paths of OCR:
any of the branches of trigeminal nerve (afferent) and the vagus nerve (efferent)
An 82-year-old patient presents for cataract surgery with placement of glaucoma tube shunts. Baseline HR 60s and BP 130s/80s. Ten minutes into the procedure the patient’s heart rate decreases from 67 bpm to 28 bpm. You ask the surgeon to relieve pressure on the eye. After 30 seconds, the patient is asystolic. What is the most appropriate next step?
Atropine 0.2 mg/kg
Consider 1 mg IVP, incrementally may increase (clinically 1-3 mg IV)
Treatment steps:
Stop- HR should return in 20 seconds
Ensure adequate depth and ventilation
Atropine/glycopyrrolate
Consider regional infiltration
An 82yo is presenting for cataract surgery with placement of glaucoma tube shunts. Ten minutes into the procedure the patient’s heart rate decreases from 67 bpm to 28 bpm. You ask the surgeon to relieve pressure on the eye. After 30 seconds, the patient’s heart rate is 42 bpm. What is the most appropriate next step?
Glycopyrrolate 0.2 mg IV
Pt experiencing sustained bradycardia as opposed to asystole
What increases IOP? (everything lol)
-Impaired aqueous drainage (glaucoma)
-Increased choroidal blood volume (vessel volume)
-Compression of the eye, damage to optic n
-Laryngoscopy/intubation/ emergence
-Hypoxia/ hypercapnia
-HTN
-SUX!
-PEEP > 15cmH2O
-Coughing, straining, vomiting (30-40 mm Hg)
-Ocular blocks (5-10 mm Hg)
-Cardiac contraction (1-2 mmHg)
-Positions- supine, prone, Trendelenburg
-Blinking (5-10 mm Hg)
-Forceful lid squeeze (70 mm Hg)
Any maneuver that increases _ pressure, increases IOP.
venous
Hemodynamic factors and their effect on IOP
Elevates IOP:
-elevated CVP
-elevated PaCO2(hypoventilation)
-elevated ABP
Decreases IOP:
-decreased CVP
-decreased PaCO2 (hyperventilation)
-decreased ABP
-decreased PaO2
Medication effects on IOP
IA
-Volatile anesthetics = decrease
-N2O = +/-
IV agents
-Prop = decrease
-Benzos = +/-
-Ketamine = +/-
-Opioids = decrease
-Mannitol = decrease
-Acetazolamide (Diamox) = decrease
NMBD
-Sux = INCREASES!!!!
-NDMR = +/-
How does Sux increase IOP?
prolonged contraction of EO muscles, fasciculations, choroidal vascular dilation and relaxation of orbital smooth muscle
2 sources of info:
-increases 5-10mmHg for 5-10 min
OR
-increases by 9mmHg for 1-4 mins up to 7min
How many mL in one eye drop?
1/20 mL
When stimulation of OCR is stopped, HR should return in _ sec
20 sec
Most significant factor on formation of aqueous humor is difference in osmotic pressure between _ _ and _
aqueous humor and plasma
Most significant factor controlling aqueous humor outflow is the diameter of the _ space in the _ meshwork
Fontana space
trabecular meshwork
Pupil dilation _ (increase/decreases) IOP. How?
increases
-volume within fontana space narrows, increasing resistance of outflow
-> ocular HTN ->glaucoma
Open angle vs closed angle glaucoma
open angle = from increased IOP from sclerotic trabecular tissue leading to decreased drainage
closed angle= obstruction from either displaced iris on posterior cornea or swelling of crystalline lens
Can glaucoma pts have atropine? What about scopalamine?
Atropine yes (ONLY VIA IV!)
Scopolamine no, causes more mydriasis = increasing IOP
Which kind of surgery is known to cause the most increase in IOP?
robotic lap cases
-> steep trend and CO2 insufflation
What can occur if a pt coughs during surgery with their eyes open?
-hemorrhage and disconcerting loss of vitreous
Intraop factors to avoid increasing IOP in glaucoma pts:
-over hydration
-prone
-trend for too long
-hypercapnia
-neck constriction
-high level insufflation
What is visual field “wipe out” in glaucoma pts?
after surgery a small percent of these pts have significant vision loss
-cause is not determined but may be due to poor perfusion, optic nerve injury/pressure, compression device
Procedure for infantile glaucoma=
goniotomy
MUST HAVE GA
Most commonly performed filtering procedure in adults =
trabeculotomy
-removes limbic tissue blocking aqueous humor drainage, using tubes or shunts
-adults can have a Retrobulb or Peribulb injection and if needed a facial n block
Patho of diabetic retinopathy (DR)
1. Chronic _ cause _ abnormalities.
2. The _ abnormalities cause impaired _ of blood flow
3. This then causes retinal _ and ischemia
4. _ and _ proteins also accumulate.
5. Neovascularization occurs and this could eventually cause retinal _
- hyperglycemia, vascular
- vascular, autoregulation
- hemorrhage
- Sorbitol and glycated proteins
- retinal detachment
2 kinds of retinal detachment:
Rhegmatogenous (tear) (more common)
or
Non-rhegmatogenous
-tractional
-exudative
Retinal Detachment
s/s
-floaters
-flashing lights
-vision loss
-shadows/clouds
-curtain like blackness
If N2O is being used in retinal detachment surgery, must be turned off for _ - _ min before injecting _ _ to prevent expansion and increased IOP.
15-30 min
sulfur hexafluoride
If pt needs surgery within 2 wks of retinal detachment surgery, which agent is contraindicated?
N2O
Purpose of sulfur hexafluoride in retinal detachment surgery:
tamponades retina onto the choroid layer is detached from
Predisposing factors for retinal detachment:
-old age
-diabetic retinopathy (HTN and DM)
-prior eye surg
-vitreal disease
-myopia
Small incisionextracapsular cataract extraction, also known as_, is the preferred method of modern cataract extraction
phacoemulsification
-small incision of 3-4mm, lens nucleus is broken apart and sucked out, new lens implant is placed
How is anesthesia given for cataract cases?
usually MAC and topical or regional
2 major preop/ intraop considerations for strabismus surgery:
these pts may also have myopathic condition (MH!!!)
-oculocardiac reflex easy to trigger!
Major postop consideration for strabismus surgery:
PONV is very common, get several agents on board to prevent
T/F All pts having strabismus surgery can have regional anesthesia and TIVA
False!
kids need GA
adults can have TIVA + regional
-most ppl prefer GA tho (give propofol, remifentanil, zofran, decadron, and non-opiate pain relief)
Surgical correction of strabismus is repositioning of _ _
extraocular muscles (EOMS)
T/F topical anesthesia is ok for retinal detachment cases?
false
-not ok for posterior chamber surgery
-better for fast surgeons and cases not requiring akinesia of eye (glaucoma or cataracts-anterior cases!)
2 main kinds of topical anesthetic for eye cases:
0.5% Proparacaine (Proxymetacaine) drops Q 5 mins, 5 times, then give LA gel, Lidocaine + 2% Methyl-cellulose
-common for cataract surgery
Ophathalmic 0.5% Tetracaine
-more common
CN VII Oculi Block/ Van Lint Method
-which muscle blocked
-how many insertion points
-how many mL
prevents blinking/squinting, part of the complete immobilization of eye
blocks: orbicularis oculi
insertions: 3
mL: 1mL LA in 1st spot, then 2-3mL in 2nd and 3rd
Analgesia of the _ precedes _ of the eye usually
globe
akinesia
Which block takes longer to work, retrobulbar or peribulbar?
Peribulbar block = 10 min
Retrobulbar = 2 min
When considering an ocular block for a pt on anitcoags, which methods are safest?
Sub-Tenons or topical anesthesia
-minimize hemorrhage risk
Which ocular hemorrhage is more threatening to the pt, arterial or venous?
arterial-from retorbulbar
T/F Retrobulbar arterial hemorrhages result in a non-compressive hematoma and can wait to be dealt with after the surgery
false!
-emergent, tell surgeon and/or ophthalmologist, stop case, may need rapid decompression(cantholysis) to prevent permanent blindness, constant monitoring of IOP
Which complication of ocular blockade results in seizures or arrest? How?
Intra-arterial injections
MOA:
-caused by forceful injection into ophthalmic artery causing retrograde flow of LA into internal carotid (LAST)
or
-forceful injection directly into optic nerve sheath
-> sending LA to midbrain structures
Retrobulbar hemorrhage s/s=
redness of eyelid or conjunctiva
increasing proptosis pain
increased IOP
direct trauma to artery or vein
Oculocardiac reflex
-s/s
-MOA
s/s: brady, arrhythmias, asystole
MOA: CN V trigeminal (afferent arc) to floor of 4th ventricle with efferent arc via vagus nerve
Unintended intra-arterial LA injection treatment:
-patent airway with O2
-stop seizure with small dose benzo, prop, or barbiturate
Unintended subarachnoid injection (total spinal) treatment:
-O2
-vasopressors
-intubation/vent if needed, spinal should wear off in few hrs)
T/F Requirements for eye surgery include total akinesia and lowered IOP
false
-new surgical techniques permit these
2 largest causes of eye injury claims comes from:
-pt moving during ophthalmic surgery
-needle trauma from orbital blocks
Which orbital block has higher risk of complications, retrobulbar or peribulbar?
retro
Which orbital block injects into the cone of the eye?
retrobulbar
Retro and Peribulbar blocks require which position for the pt?
supine with “primary gaze”
Retro and Peribulbar blocks are appropriate for which kinds of cases?
-corneal
-ANTERIOR
-lens
What is the volume difference in LA used in retro and peribulbar blocks?
R: 1.5-5mL
P: 4-6mL (up to 12mL)
Retrobulbar Block
-goal
-anesthesia
-akinesia (not total)
-abolishment of oculocephalic reflex (blocked eye won’t move when head is turned)
Retrobulbar block
-target
-ciliary nerves
-ciliary ganglion
-CN II(maybe)
-CN III
-CN IV
-CN VI
will not block CN VII
Retrobulbar Block Procedure
1. Get _ G _ tip needle
2. Draw up _ - _ mL of LA
3. Insert perpendicularly between lateral _ and medial _ of _ orbital rim.
4. Aim _ and _
5. Walk to depth of _ - _ mm
6. _ first, then inject
- 25G, blunt
- 1.5-5mL
- 1/3, 2/3, inferior
- cephalad and medially
- 25-35mm
- Aspirate
Retrobulbar Block
-usable types of LA
-Lido 2%
-Bupivacaine 0.75%
-Ropivacaine 0.75%
Retrobulbar Block
-position
sitting or supine
-with/without sedation (usually brief, deep sedation)
-pt keeps eyes neutral
A retrobulbar block has _ (more/less) insertion points and _ (more/less) volume administered compared to peribulbar blocks.
less
less
-1 insertion point. 1.5-5mL volume given for Retro
Which ocular muscle avoids being blocked with a Retrobulbar block?
Superior Oblique
-also orbicularis oculi bc CN VII isn’t blocked either
Pt receiving retrobulbar block for ophthalmic procedure…what are some drugs that may be used to sedate the patient during injection?
Propofol
Etomidate
Fentanyl/Versed
-consider pt needs
-want fast on/off
Postretrobulbar block apnea syndromeis probably due to injection of local anesthetic into the _ _ _, with spread into the cerebrospinal fluid
optic nerve sheath
Retrobulbar Block
-complications
retrobulbar hemorrhage
perforation of the globe
optic nerve injury
intravascular injection with resultant convulsions(RESULTS IN SEIZURES/CONVULSIONS RIGHT AWAY!!)
oculocardiac reflex
trigeminal nerve block
respiratory arrest
acute neurogenic pulmonary edema
Retrobulbar block
-Contraindication
Age< 15
Procedures lasting longer than 90-120 minutes
Uncontrolled cough or tremors
Disorientation or mental impairment
Excessive anxiety or claustrophobia
Language barrier or deafness
Coagulopathies
Perforated globe
Peribulbar block
-injection site
Extraconal space, needle doesn’t need to penetrate cone
1st: INFERIOR AND TEMPORAL REGIONS, same as retro, but less cephalad and medial
2nd: between medial 1/3 and lateral 2/3 of ORBITAL ROOF EDGE
Which orbital block has a “pop” to it?
Retro- pierces into the cone
Peribulbar Block
-target
ciliary nerves
CN III
CN VI
-does NOT block CN II
Peribulbar block
-position
supine
Peribulbar Block
-pros
There is less potential for intraocular or intradural injection since LA is deposited outside of muscular cone
Less risk of globe perforation
Less risk of intravascular injection
Risk of hemorrhage decreased
Risk of injury to optic nerve decreased
No need for additional lid block
Technically easier to place
-PREFERRED METHOD DUE TO LESS RISK
Peribulbar Block
-cons
More difficult to get a complete, dense block
Slower onset
Risk of ecchymosis
Sub-Tenon Block
-injection site
episcleral space via inferonasal conjunctival fornix
-between tenons capsule and sclera, diffuses from this space and blocks sensory + motor neurons
Sub-Tenon Block
-goals
Analgesia: low volumes (3-5mL) superficial
Akinesia: high volumes (8-11mL) deeper
Sub-Tenon Block
-complications
less common, shorter, duller needles
-Globe perforation
-hemorrhage
-cellulitis
-permanent visual loss
-Local anesthetic spread into cerebrospinal fluid
GA considerations for eye cases:
Antiemetics
Smooth induction/intubation
Avoid oculocardiac reflex; know how to treat if it happens
Motionless field
Smooth extubation
Consider LMA
**Requires OET: vitrectomy, trauma to eye, vitreoretinal procedures
-Airway will be away from you**
-Nitrous oxide??
Postop considerations after eye cases:
-pain with non-cataract surgeries
-multimodal pain mgmt (NSAIDs, tylenol, gabapentin)
-treat PONV! -very common
Open eye injury
-risks/complications to avoid
-avoid increasing IOP at induction/extubation
-aspiration (usually full stomach if trauma)
-avoid regional bc increases IOP with injection
-avoid trending bed
-very carefully mask ventilate-watch eyes!
Open eye injury
-best anesthesia method + why
GA is safest
- smooth IV induction (avoid coughing/bucking)
-RSI with high dose Roc = 1.2mg/kg
**-if diff airway, get ophthalmologist to come and CAREFULLY do awake FOB
-consider narcotic and lidocaine for extubation or deep extubation is no asp risk**
When to use GA for eye cases:
-long case
-pt fears
-pediatrics
-cognitive impairment/ inability to communicate
-hearing loss
-trauma/ open eye
-certain pt conditions (dementia, deafness, restless leg, OSA -debatable, tremors, claustrophobia)
-INABILITY TO LAY FLAT!!!
MAC vs GA examples
65-year-old healthy patient undergoing blepharoplasty?
MAC
-pt must be able to communicate for this type of case
MAC vs GA examples
88-year-old patient with CHF, Afib, DM undergoing extracapsular cataract extraction (ECCE) with IOL placement?
If they can lay flat and talk for 0.5 -1hr then MAC, if not, then GA
MAC vs GA examples
72-year-old patient with tremors undergoing ectropion repair?
Probably GA
-tremors = bad
MAC vs GA examples
27-year-old healthy patient undergoing orbital tumor removal?
GA
-emergent
MAC vs GA examples
45-year-old patient with HTN and DM undergoing orbital fracture repair
GA
-this is a trauma/emergent
MAC vs GA examples
58-year-old patient with OSA undergoing ptosis repair?**
“This is a nightmare situation”-Holly
MAC!
-pt needs to communicate for this kind of case but they have OSA, give sedation during LA but wake up and try to keep comfortable without obstructing
MAC considerations for eye cases
-head at top edge of table to avoid back and neck pain
-support head on headrest to prevent movement
-head above or at level of heart, avoid venous pressure in eye leading to hemorrhage
-tape head to table to prevent sudden movemnt
-restrain arms to pts side to prevent sudden movement
-place drapes so O2 doesn’t get trapped underneath
-turn off O2 when cautery/laser is in use
-<30% FiO2 goal
Can a pt with cataracts receive orbital blocks?
no, use topical
Ocular blocks last usually _ - _ hrs
2-3hrs
Sedation goal for pt receiving eye block:
deep but not too deep
awake but not talking
T/F eye drops absorb slowly compared to IV/SQ injections
false,
its BETWEEN the two
1 eye drop = _ mL
1/20 mL
-so 10% phenylephrine drop contains 5mg of phenylephrine (a shit ton compared to IV dose of 0.05-0.1mg)
Echothiophate (phospholine iodide) eye drops prolong action of _
sux
_ eye drops cause bradycardia, CHF, and BRONCHOSPASM
Timolol
Acetazolamide is often used in _ cases and can cause _ when given too quickly IV
glaucoma
confusion
Ophthalmic Meds:
Acetylcholine
-MOA
-use
MOA: cholinergic agonist
uses: miosis
Ophthalmic Meds:
Acetylcholine
-s/e
brady
brochospasm
HoTN
Ophthalmic Meds:
Acetazolamide
-MOA
-uses
MOA: carbonic anhydrase inhibitor
uses: decreases IOP, glaucoma
Ophthalmic Meds:
Acetazolamide
-s/e
confusion
drowsiness
hypoK+ + hypoNa+
met. acidosis
altered liver function tests
polyuria
renal failure
Ophthalmic Meds:
Atropine
-MOA
-uses
MOA: anticholinergic
uses: mydriasis
Ophthalmic Meds:
Atropine
-s/e
dry mouth
dry skin
fever
agitation (central anticholinergic syndrome)
Ophthalmic Meds:
Epinephrine
-MOA
-uses
MOA: alpha, beta agonist
uses: mydriasis, decrease IOP
Ophthalmic Meds:
Epinephrine
-s/e
HTN
tachycardia
Vent arrhythmias
Ophthalmic Meds:
Mannitol
-MOA
-uses
MOA: osmotic diuretic
uses: decrease IOP
Ophthalmic Meds:
Phenylephrine
-MOA
-uses
MOA: alpha adrenergic agonist
uses: mydriasis, vasoconstriction
Ophthalmic Meds:
Phenylephrine
-s/e
HTN
Ophthalmic Meds:
Tamulosin
-MOA
-uses
MOA: alpha ANTagonist
uses: benign prostatic hyperplasia (BPH)
Ophthalmic Meds:
Tamulosin
-s/e
floppy iris syndrome-tell surgeon, they may make pt stop taking this
-nothing anesthesia can do really
Ophthalmic Meds:
Timolol
-MOA
-uses
MOA: beta 1+2 ANTagonist
uses: glaucoma
Ophthalmic Meds:
Timolol
-s/e
bradycardia
bronchospasm
CHF exacerbation
How does hypothermia decrease IOP
-initial increase due to increased viscosity of aqueous humor
-decreases the formation of aqueous humor and vasoconstriction to decrease IOP
How to decrease systemic absorption of eye drops:
occlude nasolacrimal duct by pressing on inner canthus of eye
CN VII block can cause which airway issues?
Unilateral vocal cord paralysis
What is OPP?
ocular perfusion pressure = MAP - IOP
dangerously low OPP level = < 50mmHg
Which CN gives sensation to eye?
CN V - ophthalmic branch
