How butorphanol sedation affects eye exams in dogs

Abstract

OBJECTIVE: To evaluate whether sedation with intramuscular butorphanol can interfere with different variables of the ocular examination in dogs. ANIMALS: Twenty-two beagles without ophthalmic abnormalities. PROCEDURES: Each dog was examined 20&#xa0;min prior to and again just before administration of butorphanol to establish baseline data. The globe and nictitating membrane position was evaluated, and the following were recorded: menace response, dazzle reflex, corneal blink reflex, phenol red thread tear test (PRT), Schirmer tear test-1 (STT-1), pupil size (PS) measurement, and rebound tonometry. Then, butorphanol was injected intramuscularly at a dose of 0.2&#xa0;mg/kg and these procedures were repeated 10, 20, 30, and 45&#xa0;min postadministration. A sedation score graded 0 to 3 was also established at these time points. Statistical analyses were performed on quantitative data using ANOVA. RESULTS: The sedative effect was not associated with any changes in globe and nictitating membrane position; did not affect the results of the menace response, dazzle reflex, and corneal blink reflex; and had no significant effect on PRT values. However, butorphanol administration was associated with a statistically significant decrease in STT-1 and PS values (P&#xa0;<&#xa0;0.005), and a statistically significant increase in IOP (P&#xa0;<&#xa0;0.05). All these variations remained in the range of normal values. CONCLUSIONS AND CLINICAL RELEVANCE: Butorphanol administered intramuscularly at 0.2&#xa0;mg/kg provided a degree of sedation allowing eye examination, but was found to interfere with STT-1, PS, and IOP values among the diagnostic tests studied. However, these values remained within normal limits.