ENT Flashcards
1
Q
Describe the chambers and layers of the eye
A
Chambers:
- Vitreous chamber
- Anterior chamber
- Cornea to iris
- Filled with aqueous humor
- Aqueous humor drains from anterior chamber thru Schlemm’s canal into venous system
- Posterior chamber
- Iris to lens and ciliary process
Layers:
- Sclera (white part)- outermost layer
- Tough, fibrous
- Cornea- visual fx
- Curvature of cornea is where we have visual power
- Tissue where cornea meets sclera is limbis
- Uveal tract- middle
- Choroid- layer of blood vessels- bleeding of choroid can cause expulsive hemorrhage
- Iris- controls light entry (changes size of pupil)
- SNS stim → dilate pupil (iris muscle contracts)
- PSNS stim → myosis (constrict) → pupil constrict (iris sphincter muscle contract)
- Ciliary body- produces aqueous humor
- Retina (innermost layer) – nerve tissue cont. w/ optic nerve . no capillaries. Completely dependent on choroid layer to provide o2 and nourishment to retina
2
Q
What are the 6 extraocular muscles of the eye?
A
6 muscles –
- superior rectus
- inferior rectus
- medial rectus
- inferior oblique muscle
- (1-4 innervated by oculomotor nerve- CN III)
- lateral rectus muscle
- innervated by abducens nerve- CNVI.
- superior oblique muscle
- innervated by trochlear nerve- CN IV.
Sit in cone behind eye
All surround optic nerve, artery, vein, ciliary ganglion
3
Q
Describe the motor innervation of the eye?
A
-
Cranial Nerve III- Oculomotor
- innervates the superior rectus, medial rectus, inferior rectus, and inferior oblique eye muscles
- Eye movements
- Pupil constriction
- Opens eyelid
- PSNS fibers
- innervates the superior rectus, medial rectus, inferior rectus, and inferior oblique eye muscles
-
Cranial Nerve IV- Trochlear
- innervates the superior oblique muscle
- Moves eye down and outward
- innervates the superior oblique muscle
-
Cranial Nerve VI- Abducens
- innervates the lateral rectus muscle
- Moves eye lateral
- innervates the lateral rectus muscle
Sympathetic fibers from carotid plexus travel through ciliary ganglion → innervate dilator muscles
- Ex: block ciliary ganglion → fixed/dilated pupil
PSNS- CN III
4
Q
Describe the sensory innervation for the eye.
A
-
TRIGEMINAL nerve (CN V) – touch/pain
-
Ophthalmic branch (VI): 1st branch
- Innervates the upper eyelid, conjunctiva, and cornea
- Nosociliary branch (of opthalmic nerve)
- sensory to medial canthus, lacrimal sac, and ciliary ganglion
- Ciliary ganglion → provides sensory to cornea, iris, and ciliary body
- sensory to medial canthus, lacrimal sac, and ciliary ganglion
- Also regulates OCR (oculocardiac reflex)
- Nosociliary branch (of opthalmic nerve)
- Innervates the upper eyelid, conjunctiva, and cornea
-
Maxillary branch (V2): 2nd branch of 5
- Innervates lower lids
-
Ophthalmic branch (VI): 1st branch
-
Facial nerve: VII- Exits skull in stylomastoid foramen
- Supplies motor innervation to orbicularis muscle via zygomatic branch
- Ex: block CN VII → cant squeeze lid
- Innervates the lower lid
- Ex: block CN VII → cant squeeze lid
- Supplies motor innervation to orbicularis muscle via zygomatic branch
5
Q
What is normal intraocular pressure?
A
- Normal: ~ 16 mmHg (+/- 5)
-
Abnormal: > 25 mmHg
- Must maintain normal IOP to maintain normal curvature of cornea
- IO perfusion pressure related to CPP
- (MAP – IOP → how eye regulates perfusion)
- Ex: High IOP → impairs BF to optic nerve (fx effected)
6
Q
How is aqueous humor produced?
A
- Posterior chamber:
- 2/3 produced by ciliary body (~80-90%)
- → then actively moved from posterior chamber to anterior chamber by an active sodium pump mechanism.
- Active Na pump (AKA → Na-K ATPase carbonic anahydrase enzyme)
- Passive filtration: 1/3 (~20%)
- comes from passive filtration through vessels in iris. across ciliary epithelium
- Aqueous fluid is produced at a rate of 2 uL/min.
7
Q
How is aqueous humor eliminated?
A
- Fluid drains out of eye through trabecular meshwork (spongy tissue) → - into canal of Schlemm’s and the episcleral venous system (in anterior chamber) → eventually ending up at SVC and RA.
- Drainage system
- Trabecular meshwork → eventually go back into central circulation
- Anything affecting flow → cause increase IOP
- Drainage system
8
Q
What can happen if elimination of aqueous humor is impaired?
A
- Open angle glaucoma (OAG): Sclerosis of trabecular meshwork
- chronic elevation
- Closed angle glaucoma (CAG): Obstruction of Aqueous drainage from closure of anterior chamber angle
- CAG Causes:
- Iris swelling
- Anterior displacement
- CAG Causes:
- Pts already w/ narrow angle predisposed to acute increase IOP (PAIN & emergency)
9
Q
What determines intraocular pressure?
A
- A measurement of the fluid pressure inside eye
- The globe is a relatively noncompliant compartment and the volume of the internal structures is fixed, except for aqueous fluid and choroidal blood volume.
- The quantity of these two factors regulates intraocular pressure.
- The globe is a relatively noncompliant compartment and the volume of the internal structures is fixed, except for aqueous fluid and choroidal blood volume.
-
Determined by:
- Production of aqueous humor
- Drainage of aqueous humor
- Changes in choroidal blood volume or pressure
- Extraocular muscle tone
- Normal IOP: 10-20 mmHg (~ 16 and +/- 5)
- >25 mmHg, you have problem
10
Q
What can increases and decrease IOP?
A
- Drugs:
- Ketamine (?) → theoretically causes issues but does not directly
- Succinylcholine (increases by 8-10 mmHg)
- d/t
- decrease in Aqueous humor outflow
- increase in choroidal BV
- increase in CVP
- d/t
- Other:
- MOST SIG INCREASE → Laryngoscopy & Emergence
- Sympathetic Blunting
- Less manipulation of AW the better (LMA less increase than DL)
- Position changes
- Coughing, valsalva maneuver, straining, vomiting, HTN, injection of local anesthesia, laryngoscopy, hypercarbia/hypoventilation/ hypoxia, lid pressure, eye compression, forceful lid squeeze (increases to 70 mmHg), pupil mydriasis (dilation)
- Increases up to 30-40 mmHg
- MOST SIG INCREASE → Laryngoscopy & Emergence
Decrease:
- Drugs:
- Most anesthetic drugs:
- VA (excluding N2O → no effect)
- Propofol
- Etomidate
- Opioids
- NDMR
- hypertonic solutions
- Dextran
- Mannitol
- Most anesthetic drugs:
- Other: Hypotension, hypothermia, hyperventilation, pupil miosis (constriction)
11
Q
What are some anesthetics that have no effect on IOP?
A
- N2O
- Versed
- ~NDNMB
12
Q
What is acetazolamide?
MOA, S/E?
A
Carbonic anhydrase inhibitor (topical for eye)- brand Diamox
- Treatment for glaucoma
- Induces:
- decreases IOP*
- diuresis
- reduces aqueous humor production
-
K+ depletion (+/-)
- want preop labs
- SE:
- Confusion
- Drowsiness
- Low K
- Low Na
- Acidosis
- Polyuria
13
Q
What is echothiophate?
A
- Tx for glaucoma
- Irreversible cholinesterase inhibitor
- Produces:
- miosis
- Produces:
- Systemic absorption may cause total body inhibition of plasma cholinesterase
-
CAUTION:
- Prolong effects of:
- Succinylcholine
- Mivacuronium
- Toxicity w/ Ester LAs
- Prolong effects of:
-
Very long DOA:
- Need to stop 4-6 weeks preoperatively
-
CAUTION:
14
Q
Phenylephrine eye drops? s/e?
A
- Produces mydriasis
- Associated w/:
- severe HTN
- Arrythmias
- Adverse CV events
- Very high [] (1 drop = 5 mg)
15
Q
What are clycloplegics?
A
Atropine and Cyclopentolate
- Pupil mydriasis (dilation)
- Systemically absorbed
- SE: See anticholinergic symptoms
- Dry mouth
- Dry skin
- Fever
- Agitation
- disorientation, psychotic reactions
- Central anticholinergic symptoms
- SE: See anticholinergic symptoms
16
Q
Effect of acetylcholine in eye drops?
A
- Produces miosis
- Cholinergic agonist
- Causes:
- Bradycardia
- acute bronchospasm
- hypotension
17
Q
What is timolol?
A
- Tx of glaucoma
- B1/2 antagonist
- Produces:
- Miosis
- reduction of aqueous humor production
- SE:
- Bradycardia
- Bronchospasm
- CHF exacerbation
- heart block
- Issues w/ nursing infants
18
Q
NSAID use in eye drops?
A
- Ketorolac and Diclofenac
- Used for inflammation
19
Q
Scopalamine effect on eyes?
A
- Mydriasis (dilation)
- Can causes central anticholinergic syndrome
Scopalamine drug card:
-
CLASS= tertiary amine anticholinergic that crosses BBB; used for motion sickness, PONV, sedation, bronchodilation; biliary & ureteral SM relaxation; NOT used for reversal of NMB
- (Most potent anti-sialagogue (+++) & sedative anti-cholinergic) (+++)
-
MOA:
- Competitively inhibit ACh at the muscarinic receptors & decrease PNS activity (preventing decrease cAMP & cGMP);
- causes sedation by blocking Ach effects @ M1;
- increase HR by blocking the ACh effects @ M2;
- relaxes bronchial smooth muscle & decrease secretions by blocking Ach effects @ M2 & M3; also decrease GI secretions;
- Pharmacokinetics= lipid soluble; onset- 10 min; DOA- 2 hrs; E1/2- 4 hrs- may last 3-7 days; metabolized by the liver with <1% excreted unchanged in urine
- SE= sedation, post-op delerium; increase HR (+), CO, IOP; OH; arrhythmias; blurry vision; decrease secretions (+++) & GI motility; urinary retention; central anti-cholinergic syndrome, bronchodilation (+)
- CI= glaucoma, GI/GU obstruction; caution elderly
- Dose= 0.3-0.6 mg IV q 4-6 hrs, patch over 72 hours
20
Q
What is the oculocardiac reflex?
A
Aka Trigeminal-vagal reflex
- Reflex triggered:
- → pressure on globe, pain, and / or traction on extraocular muscles, retrobulbar block, orbital injections, trauma, and hypoventilation (hypercarbia and hypoxemia)
- Ex: *traction on medial rectus muscle
- Pressure on periosteum
-
Afferent limb arises from ophthalmic division of trigeminal nerve → goes to gasserian ganglion and sensory nucleus of trigeminal nerve near the 4th ventricle
-
Afferent limb synapses with motor nucleus of vagus nerve → efferent impulse that travels to heart (via vagus nerve) → leads to:
- Decreases HR
- Decrease contractility
-
Afferent limb synapses with motor nucleus of vagus nerve → efferent impulse that travels to heart (via vagus nerve) → leads to:
- → pressure on globe, pain, and / or traction on extraocular muscles, retrobulbar block, orbital injections, trauma, and hypoventilation (hypercarbia and hypoxemia)
21
Q
What is the oculocardiac reflex associated with?
A
- Bradycardia
- atrioventricular block
- ventricular ectopy
- negative inotropy
- asystole
- Occurs most often during strabismus surgery (peds pts)
- Pulling/traction of medial rectus muscle
- May be seen more often under topical anesthesia
- Occurs most often during strabismus surgery (peds pts)
22
Q
How can you reduce the occurrence of the OCR?
A
- Maintain normal ETCO2, SpO2
- Pretreat with anticholinergic
- (atropine or glycopyrrolate)→ have ready
- Considerations:
- *Pts typically elderly (increasing HR decreases coronary perfusion pressures)
23
Q
Treatment of OCR?
A
- Stop stimulus
- Assess ventilation:
- Correct hypoxia/hypercapnia (can worsen reflex)
- Admin: 100% FiO2
- normal ETCO2? SpO2?
- Correct hypoxia/hypercapnia (can worsen reflex)
- Deepen patient
- Atropine 7 ug/kg increments or Glycopyrolate
- Worsen → Epi
- Local anesthetic (lidocaine) into muscle
24
Q
Preop assessment of ophthalmic patient?
A
- High risk population/low risk surgery
- Elderly, co-morbidities
- These Pts cannot typically have outpt sx:
- Severe cardiomyopathy, pulmHTN
- Home O2
- Super morbid obese
- Known DAW
- OK to do just 1 mg Midaz
- Chronic conditions that may make it difficult to lie still and /or supine
- SOB, chronic cough, nasal drip, reflux, nausea
- Parkinson’s, Alzheimer’s or claustrophobia, mentally disabled, back pain, OSA
- These Pts cannot typically have outpt sx:
- Pediatric patient cooperation
- Non-english speaking, deaf
- Might have to consider more than MAC case
- EKG not indicated per AHA/ACC
- NEED to educate pt on what to expect. pt needs to stay still, will have blue drape over face
- 30% of eye injury during ophthalmic surgery with anesthesia were related to patients moving.
- Blindness was the outcome in all cases!
- Most problems occurred under GA, 25% under MAC.
- **Ensuring pt immobility during the procedure are therefore of the utmost importance
25
Q
Preparation for ophthalmic sx?
A
- Pre-operative ophthalmic drops
- Continue home medication regimens
- Education of being awake/still during surgery (what to expect)
- Blue drape over face
- Wont be able to see
- Duration
- Avoid over-hydration
- Control HTN
- Control BS
- No steroid coverage needed
- Dry secretions
- Sniffing/coughing → causes movement
- Treat reflux
- Good intraoperative positioning
-
Preop:
- Preexisting anticoagulants
- weigh risks vs benefits (talk to surgeon)
- don’t have to stop anticoag necessarily
- Preexisting anticoagulants
- ASA Recommendations:
- ASA 1 or 2: No routine preop lab testing before cataracts sx
- EKG done based on pt hx
- considered low risk sx
-
Preop:
26
Q
Technique for sedation for eye surgery?
A
-
Technique:
- All standard monitors on
- Supplemental oxygen by NC
- Blend w/ air if using cautery
- Positioned for comfort
- Meds: Mild/Mod sedation
- Propofol bolus @ 0.5 mg/kg for block placement only
- Midazolam 0.5-1 mg and/or Fentanyl 12.5-50 mcg
- Ex: cataract sx- just topical LA needed
- Avoid CO2 build-up under drapes
- also avoid O2 buildup- use suction
- Additional info:
- 60-70% ophthalmic sx: combo of block & MAC
- MAC:
- Less hypotension
- Faster recovery
- Less PONV
- MAC:
- 60-70% ophthalmic sx: combo of block & MAC
Other drug options
- Precedex, slower onset, nut used normally
- Ketamine causes too much dysphoria, esp in elderly
- Just need propofol when giving the actual block
27
Q
Induction considerations for general anesthesia for eye surgery?
A
- Smooth intubation
- LMA ok
- Avoid: meds increasing IOP
- Ketamine
- succinylcholine
- Blunt responses to airway maneuvers/avoid pressure on eye
- Avoid N2O
- Ex: bc injection of gases (sulfahexafluride, octofluropropane) to cause retinal tamponade
- Avoid N2O use for 3-8 wks
- Ex: bc injection of gases (sulfahexafluride, octofluropropane) to cause retinal tamponade
28
Q
Maintenance considerations for general anesthesia for eye procedures?
A
-
Avoid:
- Hypoventilation/ may want mild hyperventilation
- Ex: acidosis → increases IOP
- HTN (treat)
- bucking or moving
- direct pressure on eye
- Hypoventilation/ may want mild hyperventilation
- Typically not a very stimulating procedure once eye topicalized, may need lower anesthetic during case.
29
Q
Emergence and postoperative considerations for general anesthesia for eye procedures?
Goals for general anesthesia for eye procedures?
A
-
Emergence
- Smooth wake up
- Prevent coughing, bucking, vomiting
- Ex: Propofol, IV lidocaine, deep extubation
- Prevent coughing, bucking, vomiting
- Pretreat w/ antiemetics
- Smooth wake up
-
Post-operative
- Treat PONV
- 2fold- some risky for increase N/V (like strabismus sx) and increase IOP
- Good pain control
- Treat PONV
Goals: smooth induction, stable IOP, avoid OCR, motionless field, smooth emergence, NO N/V, No postop pain
- 30% cases req GA
- Peds
- Adults w/ cog impariement
- Watch fluids
30
Q
What is open angle glaucoma and closed-angle glaucoma? What are the treatments for each?
A
Open angle glaucome:
- Sclerosis of trabecular tissue → causing increase IOP → affecting vision
- develops slowly and bilaterally
-
-Treatment:— frequently just treated by meds, more chronic process
- Miosis (eye drops that cause miosis acetylcholine, echothiopate)
- decrease production of aqueous humor
- trabecular stretching
Closed angle glaucoma:
- Peripheral iris moves into direct contact with corneal → mechanically obstructing aqueous flow
- acute process, more rare
-
Treatment:
-
Immediate surgery
- Glaucoma is characterized by an increase in IOP to the point where blood flow is compromised (diminished capillary blood flow to the optic nerve) and the optic disc is compressed, which will eventually lead to blindness
- Avoid elevation in IOP
-
Immediate surgery
31
Q
Anesthesia management for glaucoma surgery?
A
- Surgeries performed:
- Laser trabeculoplasty
- Trabeculectomy
- Tube-shunt surgery
-
Anesthetic Management
- Continue medical management to maintain miosis
- Limit the use of anticholinergics (cause dilation)
- Avoid increases in IOP
- If severe acute glaucoma attack- dry pale painful eye:
- treat w/ Mannitol or Acetazolamide
32
Q
What is retinal detachment? Surgical treatments?
A
- Defined:
- separation of retina from its attachments to its underlying tissue w/in eye.
- Result of:
- Retinal break, hole, or tear
- Surgical treatments:
- scleral buckle
- vitrectomy
- pneumatic retinopexy (injection of gas)
- cryotherapy
- A retinal detachment is a medical emergency
34
Q
What are some anesthetic considerations when intraveitreal injection of gas is performed?
A
- Pneumatic retinopexy:
- repair retina, then use insoluble or poorly diffusible gas to tamponade retinal break against the wall of the globe
- Caution when using N2O
- Sulfur hexafluoride (SF3)
- No N2O for 10 days post-injection
- Perfluoropropane (C3F8)
- No N2O for 30 days post-injection
- Air
- No N2O for 5 days post-injection
35
Q
Anesthesia considerations for open globe injury?
A
- Concerned w/ open eye injury VS. full stomach
- Concerns: Balance b/t
- aspiration risk
- blindness risk (from increased IOP or extrusion of ocular contents)
- Concerns: Balance b/t
-
Contraindicated:
- Ophthalmic blocks
- Technique:
- RSI (d/t risk of full stomach)
- Succs- ok
- (risk of lost AW>> small increased IOP)
- DL increases IOP a lot → RSI quickens intubation and theoretically decreases IOP (rsi also decreases risk for hypoxia/hypercarbia which also increases IOP)
- Roc- 1.2 mg/kg for RSI ok
- (risk of lost AW>> small increased IOP)
- Need to limit increased IOP
- Succs admin w/ propofol helps
- Need motionless surgical field
36
Q
What is strabismus?
A
- Most common pediatric ophthalmic surgery
- Misalignment of visual axis w/:
- Amblyopia
- Diplopia
- loss of stereopsis
- Misalignment of visual axis w/:
37
Q
Considerations during strabismus procedures?
A
- Generally a myopathy of extraocular muscles
- → risk of pt having myopathy!
- LMA (peds pop)
- Risk increased:
- MH
- PONV
- OCR- oculocardiac reflex
- from direct muscle manipulation/traction
- ex: tell surgeon/remove stimulous
- bradycardia persists → admin glyco or atropine
- from direct muscle manipulation/traction
- Oculorespiratory reflex → respiratory pauses
- Afferent limb same as OCR
- Efferent limb don’t know what efferent limb is
- Not responsive to anticholinergics
- Not typically problem bc already assisting vent (LMA)
78
Q
What is a radical neck dissection?
A
- Radical neck dissection: A surgical procedure involving the removal of a tumor from the neck with an additional margin of normal tissue together with the removal of the lymph nodes from the neck. It can involve removal of the mandible and structures in the oropharynx
- The resection included the removal of:
- spinal accessory nerve
- internal jugular vein
- sternocleidomastoid muscle
- submandibular gland.
- The anatomic structures that remain:
- carotid arteries
- vagus nerve
- hypoglossal nerve
- brachial plexus
- phrenic nerve.
- A more conservative operation involves removing all the lymph nodes but sparing the spinal accessory nerve, sternocleidomastoid muscle, and internal jugular vein.
- Total Laryngectomy:
- AW ends in blind stoma
- Cut end of trachea comes to neck surface
- → wakes up with fresh trach
