Dexmedetomidine and xylazine in sheep: A study of cardiopulmonary, hematological, and gastrointestinal effects

The study aimed to compare the cardiopulmonary, hematological, and gastrointestinal effects of doses of xylazine and dexmedetomidine capable of promoting moderate sedation in sheep. Seven mixed-breed, healthy sheep underwent a crossover study with dexmedetomidine 0.005 mg.kg(-1) (DEX) and xylazine 0.075 mg.kg(-1) (XYL) intravenously. Sedation onset time, sedation score, heart rate (HR), respiratory rate (RR), systolic (SBP), mean (MBP), and diastolic (DBP) blood pressure, and spleen thickness were evaluated before treatment administration (baseline - T0) and 5 (T5), 15 (T15), 30 (T30), 45 (T45), and 60 (T60) minutes after sedation. Red blood cell (RBC), total plasma proteins (TPP), glycemia, lactatemia, and urine density were evaluated at T0, T5, T15, T30, and T60; rumen (RuM) and reticulum (ReM) motility were evaluated at T0, T15, T30, T45, and T60. The treatments promoted similar sedation scores at all time points (p > 0.05), with early onset of action of XYL (71 +/- 16" vs 111 +/- 33"). HR in DEX (63 +/- 9 bpm) was lower than in XYL (83 +/- 16 bpm) at T5 (p < 0.05). Blood pressure varied throughout the evaluation times and between treatments. There was an increase in spleen thickness at T30, coinciding with the lowest packed cell volume values, in both treatments. Values of platelet count, total leukocytes, and TPP were reduced compared to T0, but with no difference between treatments. RuM, ReM, and urine density reduced in both treatments, but the return to baseline values happened earlier with XYL. We concluded that both xylazine (0.075 mg.kg 1) and dexmedetomidine (0.005 mg.kg(-1)) promote splenic RBC sequestration and a significant reduction in rumen and reticulum motility when administered intravenously. Xylazine has an early onset of action and causes a significant increase in heart rate. Dexmedetomidine, on the other hand, has a later onset of action and a prolonged effect on sedation, urinary density, rumen motility, and reticulum motility.