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ATSUKO YAMASHITA, Osamu Sakai, Hideki Tokushige; Comparison between injectable anesthetic agents on transient cataract induced by general anesthesia in rats. Invest. Ophthalmol. Vis. Sci. 2018;59(9):5653.
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It is known that transient cataract is often developed by some general anesthesia in rodents. The transient cataract interferes with imaging of posterior eye. Inhaled anesthesia is commonly chosen for prevention to induce cataract, nevertheless there are still some negative aspects such as a difficulty in maintaining appropriate anesthetic depth. In this study, we compared the induction profiles of transient cataract between common injectable anesthetic agents in order to determine the optimum agents for ophthalmologic imaging in rats.
Male Wistar rats (5-7 weeks old) were used. Several dosages of ketamine / xylazine (KX), medetomidine / midazolam / butorphanol (MMB), ketamine / midazolam (KM), ketamine / acepromazine (KA), or pentobarbital (Pent) was intraperitoneally administered following mydriasis by dilating ophthalmic solution. After immobilization, lens opacity in both eyes was graded every 15 minutes. In addition, the anesthetic depth was evaluated by anesthetic scores based on 5 reflexes (righting, corneal, tail, and front/hind paw reflexes). These serial evaluations were performed with or without keeping body temperature (BT) at approximately 38°C.
All test agents immobilized animals around 2 min after their administrations. The maximum cataract grades with keeping BT were as follows; 4.5 in KX, 4.0 in MMB, 1.7 in KM, 0.8 in KA, and 1.7 in Pent, and those without keeping BT were as follows; 3.6 in KX, 3.5 in MMB, 1.7 in KM, 1.1 in KA, and 1.2 in Pent, respectively. Those of KX and MMB were significantly higher than those of the others. In addition, keeping body temperature tended to prevent cataract formation. KM had an adequate activity in the anesthetic depth. On the other hand, KA had a weak activity in the anesthetic depth and Pent had a respiratory depressant effect, therefore further modification should be needed when using these drugs for ophthalmologic imaging.
Combined administration of 100 mg/kg of ketamine and 4-5 mg/kg of midazolam could be optimum for ophthalmologic imaging in rats. In addition, our data suggested that the use of anesthetic agents containing an α2 adrenergic agonist should be avoided for ophthalmologic imaging in rats.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
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