Objective

To investigate motor and cardiovascular responses to dexmedetomidine or fentanyl in isoflurane-anaesthetized pigs.

Study design

Experimental, balanced, block randomized, two-group design.

Animals

A group of 16 crossbred pigs, 55 ± 8 days (mean ± standard deviation) old.

Methods

Deltoid electromyography (EMG) was recorded during isoflurane anaesthesia. Electrical stimulation using 5, 10, 20 and 40 mA of the distal right thoracic limb elicited a nociceptive withdrawal reflex (NWR), quantified by the area under the curve (AUC) for the simulation intensity versus EMG amplitude response curve. Latency to movement evoked by clamping a claw for maximum 60 seconds was noted. Arterial blood pressure and pulse rate were recorded. Data were sampled at baseline and during dexmedetomidine 0.25, 0.5, 1.0, 2.0, 4.0 and 8.0 μg kg^–1 hour^–1 or fentanyl 5, 10, 20, 40, 80 and 160 μg kg^–1 hour^–1 infusions. The influence of infusion rate on NWR AUC and spontaneous EMG was analysed using a mixed model, with p < 5%.

Results

NWR AUC increased at fentanyl 5 μg kg^–1 hour^–1 but decreased at fentanyl 40, 80 and 160 μg kg^–1 hour^–1 and dexmedetomidine 4.0 and 8.0 μg kg^–1 hour^–1. All pigs at fentanyl 80 μg kg^–1 hour^–1, and three pigs at dexmedetomidine 8.0 μg kg^–1 hour^–1 had mechanical latencies greater than 60 seconds. Spontaneous EMG activity increased accompanied by visually evident ‘shivering’ at fentanyl 5, 10 and 20 μg kg^–1 hour^–1 but decreased at dexmedetomidine 2, 4 and 8 μg kg^–1 hour^–1. Clinically relevant effects of increasing infusion rates on blood pressure or pulse rate were not observed.

Conclusion and clinical relevance

If anaesthetic plane or antinociception is evaluated in pigs, response to claw clamping and NWR will not necessarily give uniform results when comparing drugs. If only one method is used, results should be interpreted cautiously.

中文翻译：

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芬太尼或右美托咪定对异氟醚麻醉猪伤害性诱发肌肉活动的抑制和促进作用

客观的

研究异氟醚麻醉猪对右美托咪定或芬太尼的运动和心血管反应。

学习规划

实验性、平衡、区组随机、两组设计。

动物

一组 16 头杂交猪，55 ± 8 天（平均值 ± 标准差）。

方法

在异氟醚麻醉期间记录三角肌电图 (EMG)。使用 5、10、20 和 40 mA 的远端右胸肢的电刺激引起伤害性撤回反射 (NWR)，通过模拟强度与EMG 幅度响应曲线的曲线下面积 (AUC) 进行量化。注意到通过夹紧爪子最多 60 秒引起的运动延迟。记录动脉血压和脉率。在基线和右美托咪定 0.25、0.5、1.0、2.0、4.0 和 8.0 μg kg ^–1小时^–1或芬太尼 5、10、20、40、80 和 160 μg kg ^–1小时^{–1期间采集数据}输液。使用混合模型分析输注速率对 NWR AUC 和自发 EMG 的影响，p < 5%。

结果

NWR AUC 在芬太尼 5 μg kg ^-1小时^-1时增加，但在芬太尼 40、80 和 160 μg kg ^-1小时^-1以及右美托咪定 4.0 和 8.0 μg kg ^-1小时^-1时降低。芬太尼 80 μg kg ^-1小时^{-1的所有猪和 8.0 μg kg -1}小时^-1右美托咪定的三头猪的机械潜伏期均大于 60 秒。自发 EMG 活动在芬太尼 5、10 和 20 μg kg ^–1小时^–1时增加并伴有视觉上明显的“颤抖”，但在右美托咪定 2、4 和 8 μg kg ^–1小时^{–1时降低}. 未观察到增加输注速率对血压或脉率的临床相关影响。

结论和临床相关性

如果在猪中评估麻醉平面或镇痛作用，在比较药物时，对钳夹和 NWR 的反应不一定会给出一致的结果。如果只使用一种方法，则应谨慎解释结果。