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Lijun Jia, William O. Cepurna, Elaine C. Johnson, John C. Morrison; Effect of General Anesthetics on IOP in Rats with Experimental Aqueous Outflow Obstruction. Invest. Ophthalmol. Vis. Sci. 2000;41(11):3415-3419.
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purpose. To determine the effect of several common general anesthetics on
intraocular pressure (IOP) after experimental aqueous outflow
obstruction in the rat.
methods. A single episcleral vein injection of hypertonic saline was used to
sclerose aqueous humor outflow pathways and produce elevated IOP in
Brown Norway rats. Animals were housed in either standard lighting or a
constant low-level light environment. Awake IOPs were determined using
a TonoPen (Mentor, Norwell, MA) immediately before induction of
anesthesia by either isoflurane, ketamine, or a mixture of injectable
anesthetics (xylazine, ketamine, and acepromazine). For each
anesthetic, IOPs were measured immediately after adequate sedation
(time 0) and at 5-minute intervals, up to 20 minutes.
results. Awake IOPs ranged from 18 to 52 mm Hg. All anesthetics resulted in a
statistically significant (P < 0.01) reduction in
measured IOP at every duration of anesthesia when compared with the
corresponding awake IOP. With increasing duration of anesthesia,
measured IOP decreased approximately linearly for both the anesthetic
mixture and isoflurane. However, with ketamine, IOP declined to 48% ±
11% (standard lighting) and 60% ± 7% (constant light) of awake
levels at 5 minutes of anesthesia, where it remained stable. In fellow
eyes, the SD of the mean IOP in animals under anesthesia was always
greater than the corresponding SD of the awake mean. Anesthesia’s
effects in normal eyes and eyes with elevated IOP were
conclusions. All anesthetics resulted in rapid and substantial decreases in IOP in
all eyes and increased the interanimal variability in IOPs. Measurement
of IOP in awake animals provides the most accurate documentation of
pressure histories for rat glaucoma model
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