CHAPTER 49 | ANESTHESIA FOR Ophthalmic Surgery Flashcards
The afferent limb of the oculocardiac reflex:
A. CN 7
B. CN 10
C. CN 5
A. CN 7 (trigeminal nerve)
The oculocardiac reflex is triggered by pressure on the globe and by traction on the extraocular muscles as well as on the conjunctiva or on the orbital structures.
This reflex, whose afferent limb is trigeminal and efferent limb is vagal, may also be elicited by performing a regional eye block, by ocular trauma, and by direct pressure on tissue remaining in the orbital apex after enucleation.
The innermost layer of the eye:
A. Retina
B. Cornea
C. Uveal tract
A. Retina
What is the average rate of aqueous humor production?
A. 500 uL/min
B. 2uL/min
C. 4uL/min
B. 2uL/min
The average rate of aqueous humor production of 2 μL/min.
IOP (intraocular pressure) is considered abnormal if above:
A. 22 mmHg
B. 24 mmHg
C. 18 mmHg
A. 22 mmHg
IOP normally varies between 10 and 21.7 mmHg and is considered abnormal above 22 mmHg. This level varies from 1 to 2 mmHg with each cardiac
contraction.
Which of the following increases IOP?
A. Etomidate
B. Hyperventilation
C. CO2
D. Mannitol
C. CO2
TRUE or FALSE
During anesthesia, a rise in IOP can temporarily result to a visual loss.
FALSE
During anesthesia, a rise in IOP can produce permanent visual loss.
Which of the following is avoided in patients with closed-angle glaucoma?
A. Scopolamine
B. Atropine
C. Glycopyrrolate
A. Scopolamine
TRUE or FALSE
Any maneuver that increases venous pressure in the eye can elevate the IOP
TRUE
Because a rise in venous pressure produces an increased volume of ocular blood and decreased aqueous outflow, it is obvious that considerable elevation of IOP occurs with any maneuver that increases venous pressure.
Which of the following situation does NOT cause an elevation of the IOP?
A. Overhydration
B. Prone position
C. Hypercapnia
D. Trendelenburg
E. Giving a bolus of Mannitol
E. Giving a bolus of Mannitol
Maneuvers that can elevate the IOP:
Overhydration, constriction around the patient’s neck, prolonged Trendelenburg or prone
position, and hypercapnia, hypercapnia, which may induce choroidal vascular congestion!
CHOROIDAL VENOUS CONGESTION > Increased IOP!
The onset of primary congenital glaucoma is:
A. 0 - 3 y.o.
B. anytime after birth until 1 year old
C. 0 - 5 y.o.
A. 0 - 3 y.o.
Primary congenital glaucoma is classified according to age of onset, with the infantile type presenting any time after birth until 3 years of age.
Which drug is useful during examination of infantile glaucoma under general anesthesia?
A. Succinylcholine
B. Ketamine
C. Mannitol
D. Atropine
B. Ketamine
Some clinicians maintain that ketamine is a
useful drug to use for examination under anesthesia when infantile glaucoma
is part of the differential diagnosis because ketamine does not appear to spuriously lower IOP measurement, moreover, even normal infants sporadically have pressures in the mid-20s
Which of the following decreases IOP?
A. Overhydration
B. Hyperthermia
C. Hyperventilation
D. Hypoventilation
C. Hyperventilation
Hyperventilation decreases IOP, whereas asphyxia, administration of carbon dioxide, and hypoventilation have been shown to elevate IOP.
Which of these drugs can DOES not reduce the IOP?
A. Dexmedetomidine
B. Etomidate
C. Barbiturates
D. Dextran
E. Ketamine
E. Ketamine
virtually all CNS depressants, including
propofol and etomidate, dexmedetomidine, barbiturates, neuroleptics, opioids, and hypnotics, lower IOP at dose ranges for sedation and general
anesthesia in both normal and glaucomatous eyes
TRUE or FALSE
All nondepolarizing neuromuscular agents given in equipotent ED95 doses directly lower IOP by
relaxing the extraocular muscles.
TRUE
In contrast, depolarizing agents such as succinylcholine lead to an increase in IOP.
What are the mechanisms involved why IOP is elevated after giving succinylcholine?
An average peak IOP increase of about 9 mmHg is produced within 1 to 4 minutes of an intubating dose of succinylcholine which returns to baseline
typically within 7 minutes.
The ocular hypertensive effect of succinylcholine has been attributed to several mechanisms, including the tonic contraction of extraocular muscle fasciculation,6 choroidal vascular dilation, and relaxation of orbital smooth muscle.
IOP elevation and sux: 9 mmHg