Podcast
Questions and Answers
What effect do alpha-2 agonists have in the treatment of glaucoma?
What effect do alpha-2 agonists have in the treatment of glaucoma?
Which of the following medications is contraindicated when a patient is taking MAOIs?
Which of the following medications is contraindicated when a patient is taking MAOIs?
What are potential side effects of miotics (cholinergic agonists causing pupillary constriction) in glaucoma management?
What are potential side effects of miotics (cholinergic agonists causing pupillary constriction) in glaucoma management?
Which medication in glaucoma treatment mainly improves outflow of aqueous humor? select 2
Which medication in glaucoma treatment mainly improves outflow of aqueous humor? select 2
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What is a common systemic effect of mydriatics (pupillary dilators such as phenyl, epi, tropicamide) in glaucoma treatment?
What is a common systemic effect of mydriatics (pupillary dilators such as phenyl, epi, tropicamide) in glaucoma treatment?
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What is the primary purpose of using intraocular gas expansion during retinal detachment surgery?
What is the primary purpose of using intraocular gas expansion during retinal detachment surgery?
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Which local anesthetic is commonly used for cataract surgery?
Which local anesthetic is commonly used for cataract surgery?
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What complication is most closely associated with the retrobulbar block technique? select 3
What complication is most closely associated with the retrobulbar block technique? select 3
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Why must nitrous oxide (N2O) be discontinued 15-30 mins prior to the placement of the gas bubble in retinal surgery?
Why must nitrous oxide (N2O) be discontinued 15-30 mins prior to the placement of the gas bubble in retinal surgery?
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What is the necessary action if retrobulbar hemorrhage occurs during a procedure?
What is the necessary action if retrobulbar hemorrhage occurs during a procedure?
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What is the risk associated with optic nerve sheath trauma during a regional anesthetic procedure? select 2
What is the risk associated with optic nerve sheath trauma during a regional anesthetic procedure? select 2
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What is the difference between a retrobulbar block and a peribulbar block?
What is the difference between a retrobulbar block and a peribulbar block?
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Which is the only cranial nerve that is part of the central nervous system (CNS)?
Which is the only cranial nerve that is part of the central nervous system (CNS)?
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What needle depth is considered the safest for ophthalmic regional anesthesia?
What needle depth is considered the safest for ophthalmic regional anesthesia?
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Mydriatic = dilators = sympathetic stimulators
Mydriatic = dilators = sympathetic stimulators
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Miotic = constrictors = parasympathetic agonists
Miotic = constrictors = parasympathetic agonists
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What medications are known to reduce aqueous humor production? (Select all that apply)
What medications are known to reduce aqueous humor production? (Select all that apply)
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What is the effect of cycloplegic medications such as atropine, homatropine, and cyclopentolate? select 2
What is the effect of cycloplegic medications such as atropine, homatropine, and cyclopentolate? select 2
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How long should nitrous oxide be avoided in patients with a gas bubble postoperatively from a retinal detachment?
How long should nitrous oxide be avoided in patients with a gas bubble postoperatively from a retinal detachment?
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What is the target for regional ophthalmic procedures that anesthetize cranial nerves?
What is the target for regional ophthalmic procedures that anesthetize cranial nerves?
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Which regional technique provides akinesia, anesthesia, and abolishment of the oculocardiac reflex?
Which regional technique provides akinesia, anesthesia, and abolishment of the oculocardiac reflex?
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What occurs first due to differential blockade in the eye?
What occurs first due to differential blockade in the eye?
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What are the disadvantages of the peribulbar block? (Select all that apply)
What are the disadvantages of the peribulbar block? (Select all that apply)
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What regional technique is associated with fewer complications and involves local anesthetic injected into the subscleral space between Tenon's fascia?
What regional technique is associated with fewer complications and involves local anesthetic injected into the subscleral space between Tenon's fascia?
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When is a facial nerve block indicated?
When is a facial nerve block indicated?
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What is the preferred technique when performing a facial nerve block?
What is the preferred technique when performing a facial nerve block?
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What is the technique used to block the zygomatic and temporal branches of the facial nerve?
What is the technique used to block the zygomatic and temporal branches of the facial nerve?
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What are two characteristics of facial nerve blocks? (Select two)
What are two characteristics of facial nerve blocks? (Select two)
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What is expected after a retrobulbar hemorrhage? (Select all that apply)
What is expected after a retrobulbar hemorrhage? (Select all that apply)
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the optic nerve is covered by all three layers of the meninges: the dura mater, arachnoid mater, and pia mater, making it directly continuous with the brain's meningeal coverings as it is considered part of the central nervous system
the optic nerve is covered by all three layers of the meninges: the dura mater, arachnoid mater, and pia mater, making it directly continuous with the brain's meningeal coverings as it is considered part of the central nervous system
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What occurs in an open globe injury?
What occurs in an open globe injury?
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Study Notes
Glaucoma Medications
- Medications for glaucoma include mydriatics (dilating the pupils) and miotics (constricting the pupils)
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Mydriatics affect the iris dilator muscles.
- Alpha-2 agonists reduce aqueous humor production but are contraindicated with MAOIs.
- Cyclopegics paralyze the ciliary muscle, potentially causing systemic hypertension.
- Miotics are cholinergic agonists, leading to potential adverse effects like bradycardia and bronchospasm.
- Other glaucoma medications include:
- Alpha-2 agonists (reduce aqueous humor production, contraindicated with MAOIs)
- Cholinesterase inhibitors (improve aqueous humor outflow, cause miosis, and affect local anesthetic metabolism; may prolong succinylcholine and ester LA effects)
- Beta-blockers (reduce aqueous humor production)
- Carbonic anhydrase inhibitors (reduce aqueous humor production; check electrolytes preoperatively.)
- Prostaglandins (promote aqueous humor outflow; implicated in intraocular gas expansion for retinal detachment procedures).
Anesthetic Considerations for Eye Surgeries
- Procedures are short but require patient immobility.
- Prophylaxis for postoperative nausea and vomiting (PONV) is crucial.
- The patient's table should be positioned to avoid direct CRNA interaction.
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Anesthesia Type Considerations:
- MAC (Monitored Anesthesia Care): Not suitable for posterior chamber procedures.
- Local Anesthetics: Tetracaine 0.5% and lidocaine 2-4% are common choices.
- Sedation: 1mg of midazolam and 50mcg of fentanyl are usually sufficient for cataract surgery.
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Regional Blocks:
- Aim to anesthetize cranial nerves 3, 4, 5, 6, and 7.
- Common sedatives include midazolam, fentanyl, and propofol.
Regional Eye Blocks
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Retrobulbar block (RBB):
- Provides akinesia, anesthesia, and blocks the oculocardiac reflex.
- Technique: a #25g needle is inserted into the retrobulbar space, after negative aspiration, and 2-4 ml of local anesthetic is injected.
- Complications: Optic nerve damage, blood vessel damage, globe injury, vision loss, intravascular injection.
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Peribulbar block (PBB):
- Onset is slower, may not fully achieve akinesia.
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Sub-tenon/episcleral block: Involves injecting LA into the subscleral space, using a blunt curved cannula.
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Facial nerve block:
- Used for eyelid akinesia.
- Techniques: (e.g., O'Brien technique, VanLint technique).
- Disadvantages: Potential for patient discomfort and nerve proximity.
- Can lead to facial paralysis.
Complications of Eye Blocks
- Retrobulbar hemorrhage: Vessel trauma causes proptosis, conjunctival hemorrhage, increased IOP, potential optic nerve damage. Treatment involves direct pressure and lateral canthotomy.
- Globe puncture
- Optic nerve sheath trauma: LA injection can cause contralateral amaurosis (vision loss) and pupil dilation due to injection near the optic chiasm. Be prepared for respiratory arrest.
- Ocular ischemia
- Extraocular palsy and ptosis
- Bell's palsy
- Intravascular injection
Open Globe Injury
- Intraocular pressure (IOP) approaches atmospheric pressure in an open globe injury.
- Avoid further increases in IOP.
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Description
Explore the various medications used to treat glaucoma, including mydriatics and miotics. Learn about their mechanisms, contraindications, and potential side effects. This quiz covers key pharmacological agents and their impact on aqueous humor production and outflow.
