Nagelhout Ch 44 Flashcards
(299 cards)
1
Q
What is a Retrobulbar block?
A
An intraconal block that is still the most effective but carries a higher risk.
2
Q
What is a Peribulbar block?
A
An extraconal block that is a safer alternative with fewer complications.
3
Q
What is a Sub-Tenon’s block?
A
A blunt cannula approach often used in high-risk patients.
4
Q
When is topical anesthesia used?
A
Increasingly used in cataract and some glaucoma surgeries.
5
Q
When is general anesthesia used?
A
Now less common, primarily used in pediatrics or complex cases.
6
Q
What are the benefits of regional anesthesia?
A
Allows for intraoperative anesthesia, postoperative analgesia, reduced opioid use, and lower PONV incidence.
7
Q
What is the function of the Superior rectus muscle?
A
Elevates the eye; upward (supraduction).
8
Q
What is the cranial nerve associated with the Superior rectus muscle?
A
Cranial Nerve III.
9
Q
What is the function of the Inferior rectus muscle?
A
Depresses the eye; downward (infraduction).
10
Q
What is the cranial nerve associated with the Inferior rectus muscle?
A
Cranial Nerve III.
11
Q
What is the function of the Medial rectus muscle?
A
Moves the eye nasally (adduction).
12
Q
What is the cranial nerve associated with the Medial rectus muscle?
A
Cranial Nerve III.
13
Q
What is the function of the Lateral rectus muscle?
A
Moves the eye laterally (abduction).
14
Q
What is the cranial nerve associated with the Lateral rectus muscle?
A
Cranial Nerve VI.
15
Q
What is the function of the Superior oblique muscle?
A
Rotates the eyeball on its horizontal axis toward the nose (intorts and depresses the eye).
16
Q
What is the cranial nerve associated with the Superior oblique muscle?
A
Cranial Nerve IV.
17
Q
What is the function of the Inferior oblique muscle?
A
Rotates the eyeball on its horizontal axis temporally (extorts and elevates the eye).
18
Q
What is the cranial nerve associated with the Inferior oblique muscle?
A
Cranial Nerve III.
19
Q
Where do all rectus muscles originate?
A
All except the inferior oblique originate from the orbital apex around the annulus of Zinn.
20
Q
What is the role of the trochlea?
A
Redirects the superior oblique tendon.
21
Q
How do rectus muscles insert around the globe?
A
They move forward in a conal pattern and insert anterior to the globe’s equator (~40 mm long).
22
Q
How does the Superior oblique muscle travel?
A
Arises above the annulus of Zinn, becomes a tendon, passes through the trochlea, and inserts under the superior rectus.
23
Q
How does the Inferior oblique muscle travel?
A
Originates at the anterior nasal orbital floor, travels posterolaterally, and inserts inferior to the globe macula.
24
Q
What allows torsional movements of the eye?
A
The arched pathway of the superior and inferior oblique muscles.
25
What is the primary muscle that lifts the upper eyelid?
Levator palpebrae
## Footnote
Akinesia not always needed.
26
Where does the levator palpebrae originate?
Near the annulus of Zinn.
27
What is the course of the levator palpebrae?
Travels forward superior and slightly medial to the superior rectus.
28
Where does the levator palpebrae insert?
Upper eyelid.
29
What is the anesthesia implication for the levator palpebrae?
Akinesia is not required because it retracts but does not contract around the globe.
30
Does the levator palpebrae contribute to increased intraocular pressure (IOP)?
No, it is not a contributor to increased IOP.
31
What is the function of the orbicularis oculi?
Contracts/closes eyelids; akinesia often desired to reduce IOP.
32
What are the divisions of the orbicularis oculi?
Orbital, Palpebral, Tarsal.
33
How is the orbicularis oculi arranged?
In concentric rings around the eyelid.
34
What is the anesthesia implication for the orbicularis oculi?
Akinesia is typically desired to prevent involuntary eyelid movement and increased IOP due to contraction pressure around the globe.
35
What is the function of CN II (Optic)?
Vision (sensory).
36
What are the risks associated with CN II (Optic)?
Risk of CNS depression if anesthetic enters sheath.
37
What is the pathway of CN II (Optic)?
~25–30 mm long, runs from optic chiasm → optic canal → posterior globe.
38
What is unique about the optic nerve's anatomy?
It is myelinated, approx. 4 mm in diameter, and surrounded by meninges.
39
What can happen if an injection is made into the optic nerve sheath?
It can result in CNS depression or respiratory arrest via CSF spread.
40
What is the function of CN III (Oculomotor)?
Motor (primary/most extraocular muscles), parasympathetic to pupil constrictors.
41
Which muscles does CN III (Oculomotor) innervate?
Superior rectus, Inferior rectus, Medial rectus, Inferior oblique, Levator palpebrae superioris.
42
Where do parasympathetic fibers of CN III (Oculomotor) synapse?
At the ciliary ganglion.
43
What do sympathetic fibers from CN III (Oculomotor) affect?
They cause pupillary dilation (mydriasis).
44
What is the function of CN IV (Trochlear)?
Motor.
45
Which muscle does CN IV (Trochlear) innervate?
Superior oblique muscle.
46
What is unique about the anatomy of CN IV (Trochlear)?
It is the only cranial motor nerve entering orbit outside the muscle cone.
47
What is the function of CN V (Trigeminal)?
Sensory (mainly) + some motor.
48
What are the branches of CN V (Trigeminal)?
V1 – Ophthalmic, V2 – Maxillary, V3 – Mandibular.
49
What does the ophthalmic branch of CN V (Trigeminal) supply?
Pain, touch, & temperature of lacrimal, frontal, conjunctiva, iris, eyelids, forehead, nose.
50
What do the long & short ciliary nerves from the nasociliary branch of CN V (Trigeminal) supply?
Iris, cornea, ciliary body.
51
What is the function of CN VI (Abducens)?
Motor; Innervates lateral rectus.
52
What is the function of CN VII (Facial)?
Motor for muscles of the face; Innervates orbicularis oculi.
53
What is the clinical note regarding CN VII (Facial)?
Blocking this nerve helps akinesia of eyelids during eye surgery.
54
What is the function of CN X (Vagus)?
Parasympathetic and motor (larynx, heart, viscera).
55
What is the clinical relevance of CN X (Vagus)?
It is the efferent limb of the oculocardiac reflex (OCR).
56
What can CN X (Vagus) cause during eye traction or pressure?
Bradycardia or dysrhythmia.
57
What is the shape of the orbit?
The orbit is pear-shaped.
58
How do the medial walls of the orbit extend?
The medial walls extend straight back.
59
What is the angle at which the lateral walls of the orbit diverge?
The lateral walls diverge at approximately a 90-degree angle from each other.
60
What structures are contained in the apex of the orbit?
The apex contains the superior orbital fissure and inferior orbital fissure.
61
What is the function of the superior and inferior orbital fissures?
They are entry points for orbital nerves and vessels.
62
Where is the optic foramen located?
The optic foramen is located medial to the superior orbital fissure.
63
What passes through the optic foramen?
The optic nerve (CN II) and ophthalmic artery pass through the optic foramen.
64
What does the optic foramen connect?
It connects the intracranial space to the intraorbital space.
65
What is the location of the lacrimal bone?
The lacrimal bone is located just behind the medial orbital rim.
66
What is the significance of the lacrimal bone?
It is a landmark for the medial peribulbar block.
67
Where is the ethmoid bone located in relation to the lacrimal bone?
The ethmoid bone lies posterior to the lacrimal bone.
68
What is the first branch of the internal carotid artery?
The ophthalmic artery is the first branch of the internal carotid artery.
69
How does the ophthalmic artery enter the orbit?
It enters the orbit via the optic canal, usually inferolateral to the optic nerve.
70
What are the branches of the ophthalmic artery?
The branches include the central retinal artery, long and short posterior ciliary arteries, supraorbital artery, lacrimal artery, and dorsal nasal artery.
71
What does the central retinal artery supply?
The central retinal artery enters the optic nerve 8–15 mm posterior to the globe.
72
What does the supraorbital artery supply?
The supraorbital artery exits through the supraorbital notch to supply the forehead.
73
What is the origin of the infraorbital artery?
The infraorbital artery is a branch of the external carotid system via the maxillary artery.
74
Where does the infraorbital artery travel?
It travels through the infraorbital canal and exits through the infraorbital foramen.
75
What is the primary venous drainage of the orbit?
The superior ophthalmic vein is the primary venous drainage of the orbit.
76
Where does the superior ophthalmic vein drain?
It drains into the cavernous sinus via the superior orbital fissure.
77
What does the inferior ophthalmic vein originate from?
It originates from a plexus on the orbital floor.
78
What does the central retinal vein drain into?
The central retinal vein drains directly into the cavernous sinus.
79
What is an important note about orbital veins?
Orbital veins are valveless; flow is pressure-dependent, increasing the risk for retrograde infections or air embolism.
80
What enters outside the muscle cone through the superior orbital fissure?
Trochlear nerve (CN IV), Frontal nerve (branch of CN V1), Lacrimal nerve (branch of CN V1)
81
What enters inside the muscle cone through the superior orbital fissure?
Oculomotor nerve (CN III), Abducens nerve (CN VI), Nasociliary nerve (branch of CN V1)
82
What does the optic canal transmit?
The optic nerve (CN II) and ophthalmic artery.
83
What passes through the supraorbital notch?
The supraorbital nerve and artery.
84
What passes through the infraorbital foramen?
The infraorbital nerve and artery (branch of maxillary nerve CN V2).
85
What is the muscle cone?
Formed by rectus muscles around the optic nerve.
86
What is the Annulus of Zinn?
Fibrous ring at orbital apex; origin for most extraocular muscles (EOMs).
87
What is the function of the trochlea?
Pulley for the superior oblique tendon.
88
What is the significance of the lacrimal bone?
Landmark for medial peribulbar block.
89
What are the exit points for sensory nerves?
Supraorbital and infraorbital notches.
90
What is the average total orbital volume?
~30 mL
## Footnote
Globe (eyeball): 6.5–7 mL; Remaining ~23 mL: Comprised of extraocular muscles, vessels, nerves, and orbital fat.
91
What is the average orbital depth?
~48 mm (range: 42–52 mm from infraorbital rim to optic foramen).
92
Where does the orbital floor end?
Around the posterior wall of the maxillary sinus (approximately two-thirds depth).
93
Where is orbital fat present?
In both intraconal and extraconal compartments.
94
What does the orbital septum do?
Fibrous anterior boundary preventing fat herniation.
95
What is the visual axis?
Line from midpoint of cornea to macula; used for intraocular lens alignment.
96
What is the normal axial length of the globe?
23–23.5 mm.
97
What is the axial length for a hyperopic eye?
< 22 mm – may allow more space behind globe.
98
What is the axial length for a myopic eye?
> 24 mm – thinner sclera increases risk of globe puncture during needle blocks.
99
What should you ask if the axial length is unknown?
Ask about history of nearsightedness or retinal surgery.
100
What are the three tunics (coats) of the eye?
1. Fibrous (outer) layer: Sclera and Cornea. 2. Vascular (middle) layer: Choroid, ciliary body, iris. 3. Neural (inner) layer: Retina.
101
What is the limbus?
Transition zone between cornea and sclera.
102
What is the conjunctiva?
Mucous membrane covering the anterior sclera and posterior eyelids.
103
What is a staphyloma?
Protrusion of uveal tissue through a weakened scleral wall.
104
Where can staphyloma occur?
Anterior, equatorial, or posterior.
105
What is the clinical significance of staphyloma?
Common in myopia; increases risk of globe rupture with needle-based regional anesthesia.
106
What is the Tenon Capsule?
A fibrous connective tissue layer enveloping the eyeball, beginning near the corneal limbus and fused with the conjunctiva. It extends posteriorly with openings for extraocular muscles and the optic nerve.
## Footnote
Function: Forms a sliding socket for eye movement within the orbit.
107
What is the function of Orbital Connective Tissue?
A complex mesh of connective tissue septa that starts at the orbital apex and forms a 360° support structure around the globe.
## Footnote
Function: Maintains the central position of the globe and limits its displacement during motion.
108
What are the Fascial Sheaths of Extraocular Muscles?
Intermuscular membranes that connect the sheaths of all four rectus muscles, anchoring the muscles to the orbit and forming ligaments that help coordinate muscle actions.
## Footnote
Function: Enhances stability and alignment of muscles, improves efficiency of extraocular movement.
109
What are common drug classes used in ophthalmology?
Antibiotics, mydriatics (e.g., phenylephrine), miotics (e.g., pilocarpine), cycloplegics (e.g., atropine), anti-inflammatory drugs (NSAIDs and steroids), viscoelastics, and glaucoma therapies (e.g., beta blockers, prostaglandin analogs).
110
How can systemic absorption of eye drops occur?
Medications can enter systemic circulation through the outer eye membrane and the lacrimal drainage system.
## Footnote
Strategies to reduce systemic absorption include closing eyes for 60 seconds post-instillation, avoiding blinking, and applying gentle pressure to the medial canthus.
111
What is topical/intraocular anesthesia?
Common in cataract surgery, often using 2% lidocaine drops or gel, supplemented with intracameral injection of preservative-free 1% lidocaine.
## Footnote
Advantages: Safe, simple, preserves motor function, rapid recovery. Disadvantages: No akinesia, variable pain relief.
112
What is a Sub-Tenon Block?
Provides deeper analgesia than topical anesthesia, performed between rectus muscles of the globe by incising the conjunctiva and lifting Tenon’s capsule to inject local anesthetic.
## Footnote
Advantages: Good analgesia, safer than sharp needle blocks. Limitations: Variable akinesia, requires more skill and time.
113
What is the ocular regional needle block?
The ocular regional needle block is the most common and effective way to produce profound analgesia and akinesia (eye and eyelid).
114
What blocks are involved in ocular regional anesthesia?
The blocks involved are Retrobulbar and Peribulbar.
115
Which cranial nerves are affected by ocular regional anesthesia?
Cranial nerves affected include CN III (oculomotor), IV (trochlear), V (trigeminal), VI (abducens), and VII (facial).
116
Where is the ocular regional needle block performed?
This procedure is performed in the orbital epidural space.
117
What type of needle is used for a Retrobulbar Block?
A 23-gauge dull needle is used.
118
What is the insertion site for a Retrobulbar Block?
The insertion site is the infratemporal quadrant, just above the inferior orbital rim.
119
What is the recommended needle trajectory for a Retrobulbar Block?
The needle is advanced toward the orbital apex, 35 mm deep.
120
What is the anesthetic volume for a Retrobulbar Block?
2–4 mL is injected into the muscle cone.
121
What should be done post-injection in a Retrobulbar Block?
Digital pressure is applied over the closed eyelid; the globe is inspected for akinesia after a few minutes.
122
What are the complications of a Retrobulbar Block?
Complications include trauma to the optic nerve, vessels, globe, seizures from inadvertent intravascular injection, and respiratory arrest.
123
What is the risk associated with inward and upward gaze during needle insertion?
It puts the optic nerve and vessels in the needle path.
124
What is the recommended gaze direction for safety during needle insertion?
Use primary gaze (straight ahead) or down-and-out gaze.
125
What is the recommended needle depth for a Retrobulbar Block?
The recommended depth is 19–25 mm, just posterior to the globe.
126
What type of needles should be used for safer navigation?
Use dull/flat-grind needles, curved-tip, or pinhead needles.
127
What can improve patient comfort during a Retrobulbar Block?
Sedation or topical anesthetic may improve tolerance.
128
What is the impact of upward and inward gaze on the optic nerve?
It increases tension on the optic nerve and vessels, leading to a higher risk of trauma.
129
What is the primary characteristic of a Peribulbar Block?
The needle is inserted outside the muscle cone (extraconal).
130
What is the volume used in a Peribulbar Block?
The volume is larger, typically 8–12 mL.
131
What are the injection sites for a Peribulbar Block?
Common injection sites include inferotemporal, medial, or superior-temporal.
132
What is the safety advantage of a Peribulbar Block?
It has a lower risk of optic nerve injury.
133
What is the geometric method by Harvey used for?
It allows calculation of a safe redirection point based on the orbital-globe relationship.
134
What is the least vascular injection zone for retrobulbar and peribulbar blocks?
The inferotemporal zone is the most common and safest.
135
What are key safety practices for ocular regional anesthesia?
Use primary gaze or down-and-out positions, insert needle to ~25 mm depth, favor parallel approach, and consider peribulbar block in high-risk anatomies.
136
What is the purpose of the Gills-Lloyd Modified Retrobulbar Block?
Provides deep orbital anesthesia and akinesia with improved safety over the original Atkinson technique.
137
What is the needle insertion site for the Gills-Lloyd Modified Retrobulbar Block?
Transconjunctival, inferotemporal approach, parallel to lateral limbic margin (corneoscleral junction).
138
What is the depth of needle insertion for the Gills-Lloyd Modified Retrobulbar Block?
Insert needle to 25 mm (1 inch) and redirect cephalad between lateral and inferior rectus muscles after passing globe equator (~12.5 mm).
139
What is the volume/dose for the Gills-Lloyd Modified Retrobulbar Block?
Inject 1–1.5 mL of 1–2% lidocaine after negative aspiration, total ~6 mL for orbital filling.
140
What are the technique highlights for the Gills-Lloyd Modified Retrobulbar Block?
Start with a small volume peribulbar injection to reduce discomfort. Second insertion enters the muscle cone after crossing equator. Inject slowly (1 mL/10 sec), use digital pressure after injection, and monitor for pressure sensation (orbital tension = full block).
141
What are the advantages of the Gills-Lloyd Modified Retrobulbar Block?
Avoids optic nerve and vessels, safer than traditional retrobulbar, can provide globe and eyelid akinesia without need for separate CN VII block.
142
What is the purpose of the Peribulbar Extraconal Block?
Safer block option for high-risk patients (e.g., long axial length, staphylomas, previous scleral surgery).
143
What are the injection sites for the Peribulbar Extraconal Block?
Inferotemporal and/or supraorbital regions for better anesthetic spread; medial peribulbar block for eyelid akinesia or missed muscle targets.
144
What is the needle insertion technique for the Peribulbar Extraconal Block?
Insert 25 mm (1 inch) needle outside the muscle cone, directing needle parallel to or angled away from visual axis.
145
What is the volume for the Peribulbar Extraconal Block?
Large volume 10–12 mL (e.g., 6 mL inferior, 4–6 mL superior).
146
What is the technique summary for the Peribulbar Extraconal Block?
Infraorbital: inject lateral to limbic margin, bevel toward globe. Supraorbital: insert just inferior to supraorbital rim (12 o'clock). Apply positive pressure after block for drug spread and IOP control. Wait 10 minutes for anesthesia to set in.
147
What are the limitations of the Peribulbar Extraconal Block?
May not achieve full akinesia due to septal barriers; requires multiple injection sites or repeat blocks.
148
What is the purpose of the Medial Peribulbar Block?
Primary or supplemental block, especially useful for eyelid akinesia (CN VII).
149
What is the needle site for the Medial Peribulbar Block?
Insert through caruncle conjunctiva, angled toward lacrimal bone.
150
What is the needle length/depth for the Medial Peribulbar Block?
Use 0.5-inch (12 mm) needle, avoiding the puncta, canaliculi, and medial rectus muscle.
151
What is the volume for the Medial Peribulbar Block?
Inject ~3 mL or more after negative aspiration.
152
What are the advantages of the Medial Peribulbar Block?
Provides eyelid akinesia with less discomfort than Van Lint or Nadbath blocks; can be used alone or to supplement incomplete globe akinesia; avoids deep injection and globe trauma.
153
How is ocular block evaluation performed?
Akinesia of globe is evaluated: retrobulbar block ~2 minutes post-injection, peribulbar block ~10 minutes post-injection. Globe movement in all four quadrants should be assessed. Eyelid movement: if orbicular muscle still active, supplement with medial peribulbar block.
154
What is the Orbicularis Oculi Block?
Supplemental block when eyelid movement remains after retrobulbar or peribulbar anesthesia.
155
What is the technique for the Inferotemporal injection in the Orbicularis Oculi Block?
Insert 30-gauge, 0.5-in needle bevel down, tangential to the skin. Inject 1–2 mL of local anesthetic subcutaneously. Digitally spread to medial and lateral canthi—do not run the needle across the lid.
156
What is the technique for the Supranasal injection in the Orbicularis Oculi Block?
Same needle placement, using finger pressure to depress globe. Inject 1–2 mL, again bevel down and tangential to the lid. Digitally spread, followed by light pressure to prevent bleeding.
157
What is the Van Lint Technique?
Provides akinesia of orbicular muscle (eyelids) via facial nerve (CN VII) branches; alternative to medial peribulbar block when additional eyelid akinesia is needed.
158
What is the needle and injection technique for the Van Lint Technique?
Use 25–27 gauge, 1.5-in needle. First injection: inferotemporal, 1–2 mL along the lower orbital rim, then withdraw. Second injection: redirect supratemporally along upper orbital rim with 1–2 mL. Apply light pressure post-injection to reduce ecchymosis.
159
What is the issue with Positive Orbital Pressure & Chemosis?
Retrobulbar/peribulbar blocks increase orbital volume, which may increase intraocular pressure (IOP) and cause chemosis (subconjunctival edema).
160
What is the prevention/management for Positive Orbital Pressure & Chemosis?
Occurs even with small volumes (1–2 mL), though sometimes not seen with larger (12 mL). Use positive-pressure devices to reduce IOP, enhance anesthetic spread, and normalize orbital anatomy before surgery.
161
What is the Honan Intraocular Pressure Reducer?
Device: Pneumatic compression cuff used after ocular blocks.
162
What is the technique for using the Honan Intraocular Pressure Reducer?
Eye is taped shut. Place folded 4x4 gauze over eye. Honan cuff is placed over gauze and secured with Velcro head strap. Inflate pressure to 30 mm Hg (marked in yellow on gauge).
163
What is the effect of the Honan Intraocular Pressure Reducer?
Deepens anterior chamber and reduces IOP for safer surgery.
164
What are the preoperative anesthesia management considerations for eye surgery in young children?
Assess for congenital, metabolic, musculoskeletal abnormalities (e.g., malignant hyperthermia).
165
What are the preoperative anesthesia management considerations for elderly patients?
Evaluate for polypharmacy, multisystem disease, and drug interactions.
166
What are the day-of-surgery considerations for preoperative anesthesia management?
Stress reduction is critical: use kind, calm demeanor, hypnotic techniques, and progressive relaxation.
167
What should be included in the pre-op assessment?
Review mental/physical status, vital signs, ECG. Postpone surgery if any new significant findings are observed.
168
What is essential for patient evaluation before regional anesthesia?
A careful preoperative assessment is essential, evaluating for claustrophobia, severe arthritis, tremors, restless leg syndrome, and physical limitations. Mental status should also be assessed for cooperation and ability to follow instructions.
169
What should elderly patients bring on the day of surgery?
Elderly patients should bring their medication list or bottles due to common polypharmacy and unreliable medication recall.
170
Who should make the final anesthesia clearance decision?
Final anesthesia clearance should be a collaborative decision between the anesthesia provider and the attending ophthalmologist on the day of surgery.
171
What is the purpose of an ECG before anesthesia?
An ECG within the past year provides a baseline for comparison, although it may not be necessary for low-risk procedures.
172
Are routine laboratory tests required for regional anesthesia?
Routine labs are not required for regional anesthesia unless medically indicated; general anesthesia may warrant preoperative lab evaluation based on comorbidities.
173
When should general anesthesia be considered?
General anesthesia should be considered for infants, young children, patients with severe claustrophobia, uncontrolled anxiety, inability to cooperate, or procedures lasting more than 2 hours.
174
What are some indications for general anesthesia?
Indications include pediatric patients, lack of cooperation, severe claustrophobia, inability to communicate, inability to lie flat, open-eye injuries, and procedures lasting over 2 hours.
175
What are disadvantages of general anesthesia?
Disadvantages include nausea/vomiting, retching/bucking, increased intraocular pressure, aspiration, complications from medical problems, and time and expense.
176
What are the NPO policies before ocular surgery?
NPO policies vary; permissive protocols may allow light meals and clear fluids, while strict protocols may apply at some institutions.
177
What should patients do regarding home medications before surgery?
Patients should continue home medications unless directed otherwise, with exceptions for diuretics and possible adjustments for antiglycemic agents when NPO.
178
What should be considered regarding anticoagulant management?
Bleeding risk must be considered; discontinuation of anticoagulants may be needed, and decisions should involve consultation between anesthesia and surgery teams.
179
What is the risk of stopping anticoagulants?
Stopping anticoagulants can lead to potential stroke or myocardial infarction, and patients must be informed of the risks and benefits.
180
Where are regional ocular blocks frequently performed?
Regional ocular blocks are often performed outside the operating room for greater efficiency and patient comfort.
181
What is required for resuscitation readiness during regional blocks?
A fully equipped and staffed environment is required due to the risk of life-threatening complications.
182
What is included in the essential equipment checklist for anesthesia?
Essential equipment includes an oxygen source, bag-valve mask, suction, airways, ECG monitoring, blood pressure cuff, pulse oximeter, capnography, canthotomy set, ammonia capsules, and emergency medications.
183
What are the goals of sedation for ophthalmic regional blocks?
1. Decrease patient anxiety
2. Enhance cooperation and tolerance of the block
3. Improve overall surgical experience
184
What are common sedation agents used?
1. Benzodiazepines
2. Opioid analgesics
3. Non-barbiturate sedatives (e.g., propofol)
185
What are best practices for sedation?
1. Elderly patients tolerate sedation well when properly dosed.
2. Less painful blocks often require less sedation.
3. Consider the surgeon’s preference: awake and cooperative, relaxed, or sleeping.
186
What must be followed if the patient is sedated to the point of sleep?
General anesthesia fasting guidelines must be followed.
## Footnote
Propofol is an excellent choice due to its short half-life and predictable recovery.
187
What is essential for monitoring and vigilance during sedation?
Sedation is effective and safe only with continuous monitoring for potential adverse effects or oversedation.
188
What are effective sedation techniques?
1. Good rapport between patient and clinician minimizes medications necessary.
2. Intravenous benzodiazepine administration.
3. Intravenous narcotic administration.
4. Intravenous propofol administration.
189
What are common causes of discomfort resulting from regional blocks?
1. Needle injection through the skin
2. Needle penetration of the conjunctiva
3. Needle penetration of the orbital connective tissue
4. Rapid injection of anesthetic
5. Stinging from peripheral spread of anesthetic
190
What is the procedure for a patient who is asleep during a regional block?
1. Tilt head to maintain patent airway
2. Open patient’s eye in primary gaze position
3. Administer regional block
4. Administer incremental sedation as required
191
What is important for communication with awake patients during procedures?
Clear communication is essential. Patients must be informed of what to expect and instructed on how to respond if issues arise.
192
What special care must be taken with certain patients?
Special care must be taken with hearing-impaired patients and patients with language barriers. Use specific, clear language.
193
How can proper positioning improve patient comfort?
1. Place pillows under knees to reduce back strain.
2. Use padding for arthritis or musculoskeletal issues.
3. Ensure head and neck are aligned for the surgical field.
194
What standard monitors are required during monitoring and surgical visualization?
1. ECG
2. Blood pressure
3. Pulse oximetry
195
What can be used to manage carbon dioxide retention and claustrophobia during MAC cases?
Preventive techniques include tenting surgical drapes to allow airflow and using high-flow air to help clear exhaled CO₂.
196
What should be done if a claustrophobic reaction occurs?
1. Tent drapes away from face while maintaining sterility.
2. Verbally reassure the patient.
3. Assess if surgery can continue under regional block.
197
What are effective treatments for incomplete analgesia?
1. 2% lidocaine MPF eye drops
2. Subconjunctival local anesthetic injection
198
What is the sudden IOP threshold that can result in ocular content expulsion?
Sudden IOP ≥ 40 mm Hg can result in ocular content expulsion.
199
What are some causes of acute increased intraocular pressure (IOP)?
Coughing and choroidal hemorrhage.
200
What is the mechanism behind the spike in IOP due to coughing?
Elevated intrathoracic pressure → venous backflow in valveless orbital veins → IOP spike.
201
What happens during choroidal hemorrhage?
Blood fills the choroid, causing a rapid rise in IOP and may disrupt the globe unless pressure is controlled quickly.
202
Are IOP-lowering medications effective during acute phases of choroidal hemorrhage?
IOP-lowering meds may be ineffective in acute phases.
203
What strategies can help prevent coughing to reduce IOP?
Vasoconstrictive nasal drops for postnasal drip, small sips of water for dry throat, instructing patients to warn staff before coughing, encouraging throat clearing over forceful coughing, and promoting shallow breathing.
204
What medications may blunt the cough reflex but are less effective once coughing starts?
IV lidocaine or sedation.
205
What factors influence recovery time after surgery?
Mental and physical condition, and amount of sedation or anesthesia used.
206
What are the advantages of regional anesthesia for ambulatory procedures?
Less pain, lower rates of postoperative nausea, and shorter recovery times.
207
What are common causes of postoperative nausea (PONV)?
Sedation medications, elevated IOP, and ocular pain.
208
How is postoperative follow-up conducted?
Patients are called at home later in the day to check status and seen by the surgeon the next day for formal evaluation.
209
What should be followed for preoperative preparation in general anesthesia for ophthalmic surgery?
Follow appropriate fasting guidelines based on age and comorbidities, remind patients that the operative eye will be patched upon awakening, and use sedation as needed to reduce anxiety.
210
What are the agents of choice for induction and maintenance in general anesthesia?
Propofol or etomidate, as both reduce intraocular pressure (IOP).
211
What is preferred for inhalation induction?
Inhalation induction is preferred for infants and young children and also helps reduce IOP.
212
What is the effect of succinylcholine on IOP?
Succinylcholine increases IOP transiently, peaking at +9 mm Hg at 6 minutes.
213
What are the caveats of using succinylcholine in eye muscle surgery?
Sustained contraction may interfere with forced duction test and there is a theoretical risk of expulsion with open globe, but no confirmed human cases.
214
What are alternative muscle relaxants that decrease IOP?
Nondepolarizing agents.
215
What should be done to attenuate the IOP response during laryngoscopy?
Pre-treat with IV lidocaine (1.5–2 mg/kg) 1–1.5 min before.
216
What additional risks are associated with intraocular procedures?
Traction on orbital structures may trigger the oculocardiac reflex, and eye muscle surgery is associated with malignant hyperthermia and postoperative nausea.
217
What should be done after return of spontaneous breathing and reversal of NMB?
Extubate under deep anesthesia with 100% oxygen and position the patient laterally until fully awake.
218
What are the advantages of using a Laryngeal Mask Airway (LMA)?
Can be inserted without muscle relaxants and may be removed in an awake patient with less coughing.
219
What are the risks associated with LMA?
Limited airway access intraoperatively, malposition or dislodgement, and laryngospasm or coughing if anesthesia is too light.
220
What should be the focus of postoperative care?
Pain control, PONV prevention, and maintaining stable IOP.
221
What should be done if a patient experiences persistent nausea postoperatively?
Notify the ophthalmologist as it may signal increased IOP.
222
What are the priorities for managing open-globe injuries requiring general anesthesia?
Prevent aspiration and avoid IOP increases to reduce the risk of globe rupture.
223
What is the normal range for Intraocular Pressure (IOP)?
Normal IOP is 10–22 mm Hg.
224
What factors affect Intraocular Pressure (IOP)?
IOP is affected by aqueous humor production/elimination, choroidal blood volume, CVP, and extraocular muscle tone.
225
Where is aqueous humor produced?
Aqueous humor is produced in the ciliary body.
226
What is the pathway of aqueous humor flow?
Aqueous humor flows from the posterior chamber → around the iris → to the anterior chamber.
227
How does aqueous humor drain?
It drains through the canal of Schlemm into the episcleral veins.
228
What factors can increase Intraocular Pressure (IOP)?
Factors include venous congestion (e.g., coughing, Valsalva, head-down tilt) and mydriatics that decrease drainage through spaces of Fontana.
229
What are the mechanism theories for succinylcholine's effect on IOP?
Mechanism theories include tonic muscle contraction, choroidal vasodilation, and elevated CVP.
230
How does IOP increase compare with other factors?
IOP increases more with crying, Valsalva, blinking, rubbing eyes, and coughing.
231
What does clinical evidence say about succinylcholine and IOP?
There are no human cases of ocular content extrusion from succinylcholine (Moreno study), and the risk from airway loss outweighs the IOP increase.
232
What is the decision framework for using succinylcholine?
1. Is it an easy airway? 2. Is the eye viable? If easy airway + viable eye, consider nondepolarizer. If difficult airway + viable eye, use succinylcholine with pretreatment.
233
What are key takeaways regarding succinylcholine and IOP?
Succinycholine increases IOP but can be safely used when needed. Airway control is paramount; do not withhold succinylcholine if airway is difficult and globe is viable. Smooth emergence is critical to avoid IOP spikes in both open- and closed-globe injuries.
234
What are preoperative patient risk factors for ophthalmic anesthesia complications?
Anxiety and cardiovascular disease may provoke severe hypertension, cardiac dysrhythmias, and angina before surgery.
235
How can vasovagal responses due to anxiety be managed?
Vasovagal responses can be managed effectively with ammonia capsules.
236
What chronic conditions must be addressed preoperatively?
Chronic coughing from COPD, asthma, and postnasal drip must be addressed preoperatively.
237
What are common causes of complications in regional ocular blocks?
Most adverse events are due to orbital vessel trauma, globe trauma, optic nerve trauma, and patient movement.
238
What is the cause of retrobulbar hemorrhage?
Retrobulbar hemorrhage is caused by direct trauma to orbital vessels during block.
239
What are the clinical presentations of retrobulbar hemorrhage?
Clinical presentations include proptosis, subconjunctival hemorrhage, eyelid/orbital ecchymosis, and orbital pressure that may occlude central retinal artery or vein.
240
What is the onset type of retrobulbar hemorrhage?
Venous hemorrhage is gradual, while arterial hemorrhage is rapid and pronounced.
241
How is retrobulbar hemorrhage detected?
It is noted by progressive orbital pressure on palpation, and continuous digital pressure may halt venous bleeding.
242
What is the management for persistent pressure in retrobulbar hemorrhage?
If pressure persists, perform lateral canthotomy immediately and notify the ophthalmologist.
243
What is the goal of a canthotomy?
The goal is to expand orbital space and reduce pressure to prevent vision loss.
244
What is localized episcleral hemorrhage?
Localized episcleral hemorrhage is subconjunctival bleeding without proptosis, usually from local anesthetic spread.
245
What is the epidemiology of retrobulbar hemorrhage?
It is the most common complication of ocular blocks, occurring in 1% to 3% of all regional blocks.
246
What equipment is needed for the canthotomy procedure?
Equipment includes 1 straight hemostat and 1 plastic scissors.
247
What are the steps for the canthotomy procedure?
1. Inject lidocaine along the lateral canthus if possible. 2. Place hemostat in a temporal direction along lateral canthus (4–6 mm) and clamp. 3. Remove the hemostat. 4. Use plastic scissors to incise only in crush marks left by the hemostat. 5. Control local bleeding with hemostat or digital pressure.
248
What measures can prevent retrobulbar hemorrhage?
Choose least vascular areas for needle placement, avoid deep orbital injections, avoid supranasal position of gaze, and insert needle slowly.
249
What measures can prevent seizures from intravascular injection?
Choose least vascular areas for needle placement, avoid deep orbital injections, avoid supranasal position of gaze, insert needle slowly, aspirate gently before injection, avoid injection against resistance, and avoid forceful rapid injections.
250
What measures can prevent globe puncture?
Use caution in patients with increased axial length, avoid supranasal position of gaze, direct needle away from the axis of the globe, observe globe movement, insert needle slowly with bevel toward the globe, and never forcefully inject anesthetic.
251
What are the causative agents for seizures after retrobulbar injections?
Seizures have been reported after retrobulbar injections using lidocaine, lidocaine-bupivacaine combinations, and ropivacaine.
252
What is the mechanism behind seizures from intravascular injection?
Even subtoxic doses may cause seizures if injected intraarterially, as retrograde arterial flow can send anesthetic to cerebral circulation.
253
What does the Mathers survey indicate about seizures after retrobulbar blocks?
The survey of 200 ophthalmologists showed that 3 reported seizures, suggesting underreporting in the literature.
254
What are other reactions from orbital vein injection?
Orbital vein injection may cause shivering and rigor within 15 seconds, with symptoms typically resolving in about 2 minutes.
255
What is a Globe Puncture?
A globe puncture is a risk associated with ocular injections that can lead to severe complications such as ocular explosion.
256
What are the risk factors for Globe Puncture?
Globe puncture can occur with either sharp or dull needles and has been reported even by experienced practitioners.
257
How soon can Globe Puncture be diagnosed?
Diagnosis can occur 1–14 days post-injection.
258
What is the most severe outcome of Globe Puncture?
The most severe outcome is ocular explosion due to elevated intraocular pressure (IOP) from injection.
259
What are high-risk patient characteristics for Globe Puncture?
High-risk characteristics include axial length >24 mm, scleral buckling, staphyloma, enophthalmos, and supranasal gaze.
260
What increases the risk of Globe Puncture?
Increased risk is associated with multiple orbital injections and unexpected patient movement.
261
Are blunt needles proven safer for Globe Puncture?
Blunt needles are not proven safer and can still cause optic nerve trauma, globe penetration, and CNS complications.
262
What should be done if a globe puncture is suspected?
Notify the surgeon immediately if globe puncture is suspected.
263
What are the components of the optic nerve sheath?
The optic nerve sheaths are extensions of brain meninges, consisting of an outer sheath (dura mater) and inner layers (arachnoid and pia mater).
264
What is the mechanism of injury for optic nerve sheath trauma?
Inadvertent injection into the subdural/subarachnoid space can lead to tracking to the optic chiasm or brainstem.
265
What are the clinical clues for optic nerve sheath trauma?
Always check the contralateral pupil pre-block; if it constricts pre-block and then dilates post-block, suspect subarachnoid or subdural spread.
266
What is the onset time for respiratory arrest due to optic nerve sheath trauma?
Onset can be 2–5 minutes, but may be delayed up to 10–17 minutes.
267
What immediate supportive measures should be taken for respiratory arrest?
Immediate measures include airway support, ventilation, supplemental oxygen, continuous ECG and BP monitoring, and notifying an ophthalmologist.
268
What are the signs and symptoms of Globe Puncture?
Signs include increased resistance to injection, immediate pupil dilation and paralysis, rapid increase in IOP, hypotony of the globe, and intraocular hemorrhage.
269
What measures can prevent optic nerve sheath trauma?
Preventive measures include avoiding supranasal eye position, deep orbital injection, forceful injection of anesthetics, and using modified techniques.
270
What complications can arise from ocular blocks?
Complications include retinal vascular occlusion or thrombosis and decreased pulsatile ocular blood flow.
271
What is optic nerve atrophy?
Optic nerve atrophy may occur after intraocular surgery and can lead to transient contralateral amaurosis, respiratory arrest, or vision loss.
272
What is inferior rectus muscle palsy?
Inferior rectus muscle palsy can occur after retrobulbar anesthesia, leading to vertical diplopia and may require surgical correction.
273
What are the findings of Carlson et al. regarding muscle study?
Minimal myotoxicity was observed from retrobulbar injections, but direct injection into the rectus muscle can cause massive internal damage.
274
What are other causes of ptosis?
Other causes include age-related changes, superior rectus stay suture, and eyelid speculum trauma.
275
What are common patient complaints associated with facial nerve blocks?
Discomfort from cranial nerve VII (facial nerve) blocks.
276
What complications are reported with facial nerve blocks?
Prolonged Bell palsy reported with Nadbath and O’Brien techniques, likely due to direct trauma to CN VII.
277
What are serious adverse effects of facial nerve blocks?
Dysphagia, hoarseness, cough, respiratory distress caused by unintended spread of anesthetic to vagus nerve (CN X), glossopharyngeal nerve (CN IX), and spinal accessory nerve (CN XI).
278
Where do the vagus, glossopharyngeal, and spinal accessory nerves exit the skull?
These nerves exit the skull ~10 mm medial to CN VII.
279
What other observations have been noted after facial nerve blocks?
Jaw pain reported for weeks after Nadbath block; rare seizure reported with 3 mL of 2% lidocaine + epinephrine 1:200,000 during Nadbath block.
280
What was documented in the needle injury case report by Zaturansky and Hyams?
Ocular perforation during modified Van Lint block; needle penetrated globe just beneath insertion of lateral rectus muscle.
281
What is the oculocardiac reflex?
A trigeminal–vagal reflex described by Aschner in 1908.
282
What are common stimuli for the oculocardiac reflex?
Pressure on the globe, orbital structures (e.g., optic nerve), conjunctiva, and traction on extraocular muscles (especially medial rectus).
283
What are the neural pathways involved in the oculocardiac reflex?
Afferent: Long/short ciliary nerves → Ciliary ganglion → Gasserian ganglion → Ophthalmic division of the trigeminal nerve → Trigeminal sensory nucleus (in floor of 4th ventricle). Efferent: Vagus nerve → Cardioinhibitory center.
284
What clinical occurrences may trigger the oculocardiac reflex?
Local infiltration, retrobulbar or peribulbar block, and general anesthesia; more common in pediatric muscle surgeries.
285
What cardiac dysrhythmias can occur due to the oculocardiac reflex?
Acute sinus bradycardia (most common), nodal rhythms, AV block, ventricular ectopy, idioventricular rhythm, and asystole.
286
What monitoring is essential during procedures involving the oculocardiac reflex?
Continuous ECG monitoring is essential.
287
What are the management steps for addressing dysrhythmias from the oculocardiac reflex?
1. Ask surgeon to stop stimulation. 2. Assess oxygenation, ventilation, anesthetic depth. 3. Dysrhythmia may resolve spontaneously. 4. If unresolved, administer IV atropine (2–3 mg for full vagal blockade) or consider glycopyrrolate for milder cases. 5. Surgeon may resume once rhythm stabilizes. 6. If reflex recurs, repeat process. 7. Reflex fatigues with repeated stimulation. 8. Pre-treatment with atropine or glycopyrrolate may help—especially in children.
288
What is the most common ocular injury from general anesthesia?
Corneal abrasion caused by corneal drying and direct trauma (e.g., mask injury).
289
How can corneal abrasions be prevented during general anesthesia?
Ensure eyelids are closed and taped.
290
What is the most frequent cause of surgical complications?
Movement during surgery caused by coughing and bucking.
291
What can lead to movement during surgery?
Inadequate muscle relaxants and no nerve stimulation.
292
What causes chemical injury during procedures?
Prep solution spills; flush with saline immediately.
293
What complications can arise from improper patient positioning during MAC or GA?
Central retinal artery occlusion, especially in prone cases.
294
How can improper patient positioning be prevented?
Use adequate padding, perform periodic eye checks, and use eye protection (e.g., foam headrests, gel donuts).
295
What should be done if a patient reports symptoms post-op?
Request ophthalmology consult.
296
What are the challenges in ophthalmic anesthesia?
Complex comorbidities, multiple pharmacologic interactions in elderly, pediatric-specific airway and respiratory risks (e.g., chronic URIs).
297
What trends are observed in ophthalmic anesthesia?
Topical anesthesia is becoming common for cataracts; increased demand for regional blocks due to advances in retinal surgery, corneal transplants, adult strabismus, and glaucoma surgery.
298
What are the benefits of orbital regional blocks?
Less postoperative pain, reduced need for opioids, reduced PONV.
299
When is general anesthesia still preferred?
For children, trauma patients, and patients not suited for regional/topical anesthesia.
