Effects of three commonly used anesthetics on intraocular pressure in mouse

To investigate the effects of three commonly used general anesthetics on intraocular pressure (IOP) in mouse.

Fifteen 2-3-month-old C57BL/6J mice were randomly divided into three groups (each group, n=5). A non-invasive TonoLab tonometer (Icare LAB, Icare Finland Oy, Espoo, Finland) was used to measure IOP at 0, 5, 10, 15, 20, 30 min after mice were anesthetized, respectively, by intraperitoneal injection of sodium pentobarbital (150 mg/kg), chloral hydrate (500 mg/kg) and a mixture of ketamine and xylazine (75 mg/kg and 13.6 mg/kg). IOP were obtained in the daytime and nighttime. Anterior segment was photographed and palpebral fissure height was measured offline.

Immediately after anesthesia, the averaged IOPs in the three groups were 17.2 ± 1.5, 16.7 ± 1.4 and 17.3 ± 2.4 mmHg in the daytime and 19.3 ± 2.1, 21.3 ± 1.1 and 21.7 ± 1.5 mmHg in the nighttime. Thereafter, the averaged IOPs in sodium pentobarbital and chloral hydrate groups showed a trend of decline. Then IOPs became stable at 10-15 min after anesthesia. In contrast, the IOPs of ketamine and xylazine injected group increased to 23.7-25.1 mmHg at 10-15 min in the daytime and 26.1-27.7 mmHg in the nighttime. Compared to chloral hydrate and sodium pentobarbital treated mice (2.4 ± 0.1 mm, 1.7 ± 0.0 mm), ketamine and xylazine injected animals had significantly increased palpebral fissure height (3.6 ± 0.3 mm, p<0.01).

General anesthetics have a large impact on mouse IOP. Sodium pentobarbital and chloral hydrate reduce but the ketamine and xylazine mixture increases mouse IOP. IOP levels become stabilized at 10 to 15 min after anesthesia. The ketamine and xylazine cocktail mediated elevation of palpebral fissure height may be associated with an increasing of intraorbital pressure. Measurement performs at 10-15 min after anesthesia may obtain more reliable IOPs.