The Cardiovascular Response of Sheep to Tiletamine–Zolazepam and Butorphanol Tartrate Anesthesia

Abstract

Butorphanol tartrate (0.5 mg/kg intravenously [IV]) was administered to six ewes (group 1), 10 minutes before administration of tiletamine-zolazepam (12 mg/kg IV). In six ewes (group 2), butorphanol tartrate and tiletamine-zolazepam were administered simultaneously. Time of administration of butorphanol did not alter hemodynamics or duration of anesthesia significantly. Anesthesia was adequate for 25 to 45 minutes (mean, 31 min) in group 1. The sheep in group 2 were anesthetized effectively for 25 to 50 minutes (mean, 39 min). Neither dosing regimen caused significant changes in right atrial pressure, heart rate, pulmonary vascular resistance, or pulmonary capillary wedge pressure. Mean arterial blood pressure (MABP) decreased an average of 18% from baseline values of 113 mm Hg to a minimum of 84 mm Hg at minute 60 in group 1, and from 111 mm Hg to 92 mm Hg at minute 75 in group 2. The decrease was significant only for group 1. Cardiac output (CO) was significantly decreased 24% from 6.6 L/min at minute 45 in group 1, and 32% from 6.3 L/min at minute 15 in group 2. Systemic vascular resistance (SVR) was increased significantly at minute 15, 11% in group 1 and 37% in group 2. Mild respiratory acidosis was measured by significant decreases in arterial pO2 and pH and a significant increase in pCO2 without significant changes in HCO3-. Results of this study show that (1) tiletamine-zolazepam and butorphanol tartrate produce adequate anesthesia for 25 to 50 minutes; (2) the cardiovascular and anesthetic effects of the dosing schedules were similar; and (3) tiletamine-zolazepam and butorphanol result in decreased CO and MABP with a concomitant increase in SVR, and mild respiratory acidosis.

Effects of acepromazine and butorphanol on tiletamine-zolazepam anesthesia in llamas

“…24 In horses, acepromazine (0.025 mg/kg, IM) prevents the bradycardia and hypertension induced by romifidine. 25 Mean arterial blood pressure and DAP were lower in acepromazine-treated llamas than in saline solutiontreated llamas, and these findings are consistent with the vasodilating effects of acepromazine. 6 The reported effects of butorphanol on heart rate are variable.…”

“…In TZ-anesthetized rats, butorphanol caused transient bradycardia 21 but did not significantly affect heart rate in TZ-anesthetized sheep. 25 Arterial pressure monitoring by use of oscillometric devices is a noninvasive method in routine clinical use; however, the position of the cuff in relation to the patient' s aortic root and the size of the cuff can cause erroneous readings. 18 Butorphanol had no significant effect on blood pressure, a finding consistent with the effects of butorphanol in TZ-anesthetized goats.…”

Effects of tiletamine-zolazepam anaesthesia on plasma antioxidative status and some haematological parameters in sheep

“…These results are attributable to the action of the ovine spleen as a result of sedation and anaesthesia. In laboratory studies, awaked sheep had an increased PCV and Hb concentration due to splenic contraction (Howard et al, 1990). As the ovine spleen may sequester up to 25% of the RBC, increases in circulating catecholamines in the excited and awake animal can quickly increase PCV and Hb concentrations.…”

“…As the ovine spleen may sequester up to 25% of the RBC, increases in circulating catecholamines in the excited and awake animal can quickly increase PCV and Hb concentrations. Conversely, as the sheep were sedated or anaesthetised, the spleen sequestered RBC, resulting in a lower systemic RBC count, PCV and Hb concentration (Howard et al, 1990).…”

Review: Telazol – a review of its pharmacology and use in veterinary medicine

“…The increase was attributed to an increase in heart rate (Hellyer rt ul., 1989). Decreased cardiac output was observed in horses given xylazine-Telazol and in sheep given butorphanol-Telazol (Hubhell el al., 1989;Howard et al, 1990). In calves receiving xylazine-Telazol, cardiac output only decreased transiently which may be attributed to an increase in afterload and probably a decrease in heart rate (Lin rt ul., 1991).…”