Objective

To evaluate the effects of constant rate infusions (CRIs) of dexmedetomidine and remifentanil alone and their combination on minimum alveolar concentration (MAC) of sevoflurane in dogs.

Study design

Randomized crossover experimental study.

Animals

A total of six (three males, three females) healthy, adult neutered Beagle dogs weighing 12.6 ± 1.4 kg.

Methods

Anesthesia was induced with sevoflurane in oxygen until endotracheal intubation was possible and anesthesia maintained with sevoflurane using positive-pressure ventilation. Each dog was anesthetized five times and was administered each of the following treatments: saline (1 mL kg^–1 hour^–1) or dexmedetomidine at 0.1, 0.5, 1.0 or 5.0 μg kg^–1 loading dose intravenously over 10 minutes followed by CRI at 0.1, 0.5, 1.0 or 5.0 μg kg^–1 hour^–1, respectively. Following 60 minutes of CRI, sevoflurane MAC was determined in duplicate using an electrical stimulus (50 V, 50 Hz, 10 ms). Then, CRI of successively increasing doses of remifentanil (0.15, 0.60 and 2.40 μg kg^–1 minute^–1) was added to each treatment. MAC was also determined after 30 minutes equilibration at each remifentanil dose. Isobolographic analysis determined interaction from the predicted doses required for a 50% MAC reduction (ED₅₀) with remifentanil, dexmedetomidine and remifentanil combined with dexmedetomidine, with the exception of dexmedetomidine 5.0 μg kg^–1 hour^–1, obtained using log-linear regression analysis.

Results

The sevoflurane MAC decreased dose-dependently with increasing infusion rates of dexmedetomidine and remifentanil. Remifentanil ED₅₀ values were lower when combined with dexmedetomidine than those obtained during saline–remifentanil. Synergistic interactions between dexmedetomidine and remifentanil for MAC reduction occurred with dexmedetomidine at 0.5 and 1.0 μg kg^–1 hour^–1.

Conclusions and clinical relevance

Combined CRIs of dexmedetomidine and remifentanil synergistically resulted in sevoflurane MAC reduction. The combination of dexmedetomidine and remifentanil effectively reduced the requirement of sevoflurane during anesthesia in dogs.

中文翻译：

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右美托咪定，瑞芬太尼及其组合的恒定速率输注对狗体内七氟醚最低肺泡浓度的影响。

目的

评估右美托咪定和瑞芬太尼及其组合对狗体内七氟醚最低肺泡浓度（MAC）的恒定速率输注（CRI）的影响。

学习规划

随机交叉实验研究。

动物

共有六只（三只雄性，三只雌性）健康的成年绝育的比格犬，体重为12.6±1.4公斤。

方法

用七氟醚在氧气中诱导麻醉，直到可以进行气管插管，并通过正压通气使用七氟醚维持麻醉。每只狗均麻醉五次，并进行以下每种治疗：盐水（1 mL kg ^–1小时^–1）或右美托咪定以0.1、0.5、1.0或5.0μgkg ^–1负荷剂量在10分钟内静脉内注射，然后CRI分别为0.1、0.5、1.0或5.0μgkg ^–1小时^–1。CRI 60分钟后，使用电刺激（50 V，50 Hz，10 ms）一式两份测定七氟醚MAC。然后，连续增加瑞芬太尼（0.15、0.60和2.40μgkg ^–1分钟^–1）的CRI）添加到每个处理中。在每种瑞芬太尼剂量平衡30分钟后，还测定了MAC。等效线描记法分析确定了瑞芬太尼，右美托咪定和瑞芬太尼联合右美托咪定与MAC减少50％MAC（ED ₅₀）所需的预测剂量之间的相互作用，但右美托咪定5.0μgkg ^–1小时^–1除外，使用对数线性回归分析获得。

结果

七氟醚MAC随着右美托咪定和瑞芬太尼的输注速率增加而剂量依赖性降低。当与右美芬太尼合用时，与右美托咪定合用时，瑞芬太尼ED ₅₀值较低。右美托咪定在0.5和1.0μgkg ^–1小时^–1时发生右美托咪定和瑞芬太尼之间的协同相互作用以降低MAC 。

结论与临床意义

右美托咪定和瑞芬太尼的联合CRI协同作用导致七氟醚MAC减少。右美托咪定和瑞芬太尼的组合有效降低了狗麻醉期间对七氟醚的需求。