Escobar A, Pypendop B H, Siao K T, Stanley S D, Ilkiw J E
Department of Surgical and Radiological Sciences, School of Veterinary Medicine, University of California, Davis, CA 95616, USA.
J Vet Pharmacol Ther. 2012 Apr;35(2):163-8. doi: 10.1111/j.1365-2885.2011.01301.x. Epub 2011 Apr 27.
This study reports the effects of dexmedetomidine on the minimum alveolar concentration of isoflurane (MAC(iso) ) in cats. Six healthy adult female cats were used. MAC(iso) and dexmedetomidine pharmacokinetics had previously been determined in each individual. Cats were anesthetized with isoflurane in oxygen. Dexmedetomidine was administered intravenously using target-controlled infusions to maintain plasma concentrations of 0.16, 0.31, 0.63, 1.25, 2.5, 5, 10, and 20 ng/mL. MAC(iso) was determined in triplicate at each target plasma dexmedetomidine concentration. Blood samples were collected and analyzed for dexmedetomidine concentration. The following model was fitted to the concentration-effect data: [Formula in text] where MAC(iso.c) is MAC(iso) at plasma dexmedetomidine concentration C, MAC(iso.0) is MAC(iso) in the absence of dexmedetomidine, I(max) is the maximum possible reduction in MAC(iso), and IC(50) is the plasma dexmedetomidine concentration producing 50% of I(max). Mean ± SE MAC(iso.0), determined in a previous study conducted under conditions identical to those in this study, was 2.07 ± 0.04. Weighted mean ± SE I(max), and IC(50) estimated by the model were 1.76 ± 0.07%, and 1.05 ± 0.08 ng/mL, respectively. Dexmedetomidine decreased MAC(iso) in a concentration-dependent manner. The lowest MAC(iso) predicted by the model was 0.38 ± 0.08%, illustrating that dexmedetomidine alone is not expected to result in immobility in response to noxious stimulation in cats at any plasma concentration.
本研究报告了右美托咪定对猫异氟烷最低肺泡浓度（MAC(iso)）的影响。使用了6只健康成年雌性猫。此前已测定每只猫的MAC(iso)和右美托咪定的药代动力学。猫用异氟烷加氧气进行麻醉。使用靶控输注静脉给予右美托咪定，以维持血浆浓度为0.16、0.31、0.63、1.25、2.5、5、10和20 ng/mL。在每个靶血浆右美托咪定浓度下重复测定三次MAC(iso)。采集血样并分析右美托咪定浓度。将以下模型拟合到浓度-效应数据：[文中公式]，其中MAC(iso.c)是血浆右美托咪定浓度为C时的MAC(iso)，MAC(iso.0)是无右美托咪定时的MAC(iso)，I(max)是MAC(iso)的最大可能降低值，IC(50)是产生I(max)的50%的血浆右美托咪定浓度。在与本研究相同条件下进行的先前研究中测定的平均±标准误MAC(iso.0)为2.07±0.04。该模型估计的加权平均±标准误I(max)和IC(50)分别为1.76±0.07%和1.05±0.08 ng/mL。右美托咪定以浓度依赖性方式降低MAC(iso)。该模型预测的最低MAC(iso)为0.38±0.08%，说明单独使用右美托咪定在任何血浆浓度下都不太可能使猫在受到有害刺激时保持不动。
