School of Veterinary Medicine, Murdoch University, Australia.
Clinic for small domestic animals, University of Veterinary Medicine Hannover, Germany.
Lab Anim. 2021 Oct;55(5):443-452. doi: 10.1177/0023677220983366. Epub 2021 Feb 27.
Alpha receptor agonists (alpha-agonists) are useful sedative and analgesic agents in sheep, but have adverse pulmonary effects, which are reportedly similar between different alpha-agonists. This randomized crossover study compared pulmonary function after intravenous administration of an alpha-agonist, either xylazine or an equipotent dose of medetomidine in 34 female sheep anaesthetized twice. Pulmonary function was assessed using spirometry, volumetric capnography, arterial blood gas analysis 1 min prior to, and 5 and 10 min after administration of the allocated alpha 2 agonist drug. Pulmonary structural changes were subsequently assessed using computed tomography (CT). Tachypnoea or hypoxaemia prompted reversal with atipamezole and exclusion of data. Data were analysed for a fixed effect of drug using a mixed effect linear model with significance set at < 0.05. Ten sheep administered xylazine required atipamezole while none of sheep receiving medetomidine did. Xylazine produced significantly higher respiratory frequency, airway pressures, airway resistance and arterial carbon dioxide (CO), and lower dynamic compliance, tidal volume, CO elimination and end tidal CO tension and arterial oxygen tension than medetomidine. This was associated with a significantly lower % of aerated tissue and higher % poorly and non-aerated tissue in CT images of sheep receiving xylazine versus medetomidine. In conclusion, xylazine administration produced marked decreases in pulmonary function, in ventilated isoflurane anaesthetized sheep, when compared to an equipotent dose of medetomidine when administered as an intravenous bolus supporting the use of medetomidine when alpha-agonists are required.
α受体激动剂（α-agonists）是绵羊中有用的镇静和镇痛剂，但具有不良的肺效应，据报道不同的α-agonists 之间相似。这项随机交叉研究比较了静脉注射α-agonist（赛拉嗪或等效力剂量的右美托咪定）后 34 只麻醉绵羊的肺功能，这些绵羊被麻醉两次。使用肺活量计、体积碳酸图、动脉血气分析在给予分配的α2 激动剂药物前 1 分钟以及给药后 5 分钟和 10 分钟评估肺功能。随后使用计算机断层扫描（CT）评估肺结构变化。呼吸急促或低氧血症促使使用阿替美唑逆转，并排除数据。使用混合效应线性模型分析药物的固定效应，显著性水平设为<0.05。给予赛拉嗪的 10 只绵羊需要阿替美唑，而接受右美托咪定的绵羊则不需要。与右美托咪定相比，赛拉嗪显著增加呼吸频率、气道压力、气道阻力和动脉二氧化碳（CO），并降低动态顺应性、潮气量、CO 清除率和呼气末 CO 张力以及动脉氧分压。这与接受赛拉嗪的绵羊的 CT 图像中的充气组织比例明显降低和充气不良和未充气组织比例明显升高有关，而接受右美托咪定的绵羊则没有。结论，与静脉注射等效力剂量的右美托咪定相比，赛拉嗪给药会导致麻醉异氟烷的绵羊肺功能明显下降，支持在需要使用α-agonist 时使用右美托咪定。
