We compared yohimbine (Y, 0.25 mg/kg IV), tolazoline (T, 2 mg/kg IV), atipamezole (A, 0.1 mg/kg IV) and 0.9% saline (S, 1 ml IV) after medetomidine (M, 0.02 mg/kg IV; 6 goats) and xylazine (X, 0.15 mg/kg IV; 6 goats). Temperature (TEMP), respiratory rate (RR) and heart rate (HR) were recorded at baseline (BL), 10, 20 and 30 minutes after alpha-2 agonists and 10, 20, 30 and 60 minutes after alpha-2 antagonists or S. Arterial pH-blood gases (BL; 30 minutes post-agonist; 30 minutes post-antagonist) and time intervals from antagonist (or S) to sternal recumbency (TSL), standing (TSD), and walking (TWC) were measured. Sedation was assessed by response to noise and analgesia assessed by compression (0-12 kg) on a forelimb (BL; 15 minutes post-agonist; 15 minutes post-antagonist). Statistical tests, repeated measures or one way ANOVA and Tukey-Kramer for most variables and unpaired T tests for TSL, TSD, TWC; were used with P < 0.05 considered significant. Both alpha-2 agonists sedated goats and increased tolerated compression; A, T and Y, but not S, reduced tolerated compression following X; A and T but not Y or S, reduced tolerated compression after M. HR and RR varied over time after X or M. Both alpha-2 agonists decreased HR; A and T elevated HR; Y and S did not. TEMP decreased in all groups; after A, TEMP progressed toward BL. PaCO2 increased after both alpha-2 agonists. S did not affect PaCO2; A, T and Y returned PaCO2 to BL. PaO2 varied among goats and groups. With X, TSL after A, T, Y and S were 0.6 ± 0.43, 0.6 ± 0.48, 0.5 ± 0.32 and 9.6 ± 10.46 minutes, respectively, and not significantly different. With M, TSL after A, T, Y and S were 1.4 ± 0.89, 9 ± 6.96, 8.4 ± 15.45 and 82.6 ± 40.53 minutes, respectively; times for A, T, and Y were different from S; A was different from T. With X, TSD after A, T, Y and S were 1 ± 0, 3.1 ± 3.01, 1.2 ± 0.57 and 25.4 ± 34.83 minutes, respectively and not significantly different. For M, TSD in A, T, Y and S groups, 1.6 ± 0.89, 28.5 ± 16.97, 12 ± 16.55 and 89.4 ± 34.78 minutes, respectively, were different; A, T and Y were different from S; A was different from T. With X, TWC after A, T, Y and S were 1 ± 0, 4 ± 3.16, 4.2 ± 4.36 and 26.6 ± 35.08 minutes, respectively, and not significantly different. For M, TWC after A, T, Y and S, 1.8 ± 0.84, 30.4 ± 18.39, 13.3 ± 17.44 and 92 ± 34.41 minutes, respectively, were different; A, T and Y were different from S; A was different from T. A, T and Y caused variable antagonism of X and M. A was effective, but caused side effects (vocalization, agitation, head and body-shaking, piloerection, and defecation).
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