Different structurally related phenylpiperidine opioids exhibit different isoflurane‐sparing effects in cats. Because minimum alveolar concentration (MAC) in cats is affected only by very high plasma concentrations of some phenylpiperidine opioids, we hypothesized these effects are caused by actions on nonopioid receptors. Using a prospective, randomized, crossover design, six cats were anesthetized with isoflurane, intubated, ventilated, and instrumented. Isoflurane MAC was measured in triplicate using a tail‐clamp and bracketing technique. A computer‐controlled intravenous infusion using prior pharmacokinetic models targeted plasma concentrations of 60 ng/ml fentanyl, 10 ng/ml sufentanil, or 500 ng/ml alfentanil, and isoflurane MAC was measured in duplicate. Next, naltrexone 0.6 mg/kg was administered to cats hourly during the opioid infusion, and isoflurane MAC was measured in duplicate. Blood was collected during MAC determinations to measure opioid concentrations. Responses were analyzed using repeated measures ANOVA with significance at p < .05. Alfentanil and sufentanil decreased isoflurane MAC by 16.4% and 6.4%, respectively, and these effects were completely reversed by naltrexone. Fentanyl had no significant effect on isoflurane MAC. Alfentanil and sufentanil modestly reduce isoflurane MAC via agonist effects on opioid receptors. However, these effects are too small to justify clinical use of phenylpiperidine opioids as single agents to reduce MAC in cats.

中文翻译：

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苯哌啶阿片类药物对猫中异氟烷最低肺泡浓度的影响。

不同结构上相关的苯基哌啶类阿片在猫中表现出不同的异氟醚保护作用。由于猫中的最低肺泡浓度（MAC）仅受某些苯基哌啶类阿片类药物的极高血浆浓度影响，因此我们推测这些影响是由对非阿片类药物受体的作用引起的。使用前瞻性，随机，交叉设计，六只猫用异氟烷麻醉，插管，通风和器械化。异氟烷MAC使用尾夹和括号技术一式三份进行测量。使用先前的药代动力学模型进行计算机控制的静脉输注，以一式两份测量血浆浓度为60 ng / ml芬太尼，10 ng / ml舒芬太尼或500 ng / ml阿芬太尼，以及异氟烷MAC。接下来，在阿片类药物输注期间每小时对猫给药纳曲酮0.6 mg / kg，一式两份地测量异氟烷MAC。在MAC测定期间收集血液以测量阿片样物质的浓度。使用重复测量方差分析对反应进行了分析，在p  ＜.05。阿芬太尼和舒芬太尼分别使异氟烷MAC降低16.4％和6.4％，而纳曲酮完全逆转了这些作用。芬太尼对异氟烷MAC无明显影响。阿芬太尼和舒芬太尼通过对阿片受体的激动作用适度降低异氟烷MAC。但是，这些作用太小，不足以证明临床上将苯基哌啶类阿片类药物作为减少猫MAC的单一药物是合理的。