Spadavecchia Claudia, Levionnois Olivier, Kronen Peter W, Leandri Massimo, Spadavecchia Luciano, Schatzmann Urs
Anesthesiology Section, Department of Clinical Veterinary Sciences, Vetsuisse Faculty, University of Berne, Langassstrasse 124, 3012 Berne, Switzerland.
Am J Vet Res. 2006 May;67(5):762-9. doi: 10.2460/ajvr.67.5.762.
To investigate effects of isoflurane at approximately the minimum alveolar concentration (MAC) on the nociceptive withdrawal reflex (NWR) of the forelimb of ponies as a method for quantifying anesthetic potency.
7 healthy adult Shetland ponies.
Individual MAC (iMAC) for isoflurane was determined for each pony. Then, effects of isoflurane administered at 0.85, 0.95, and 1.05 iMAC on the NWR were assessed. At each concentration, the NWR threshold was defined electromyographically for the common digital extensor and deltoid muscles by stimulating the digital nerve; additional electrical stimulations (3, 5, 10, 20, 30, and 40 mA) were delivered, and the evoked activity was recorded and analyzed. After the end of anesthesia, the NWR threshold was assessed in standing ponies.
Mean +/- SD MAC of isoflurane was 1.0 +/- 0.2%. The NWR thresholds for both muscles increased significantly in a concentration-dependent manner during anesthesia, whereas they decreased in awake ponies. Significantly higher thresholds were found for the deltoid muscle, compared with thresholds for the common digital extensor muscle, in anesthetized ponies. At each iMAC tested, amplitudes of the reflex responses from both muscles increased as stimulus intensities increased from 3 to 40 mA. A concentration-dependent depression of evoked reflexes with reduction in slopes of the stimulus-response functions was detected.
Anesthetic-induced changes in sensory-motor processing in ponies anesthetized with isoflurane at concentrations of approximately 1.0 MAC can be detected by assessment of NWR. This method will permit comparison of effects of inhaled anesthetics or anesthetic combinations on spinal processing in equids.
研究异氟烷在约最低肺泡浓度（MAC）时对小马前肢伤害性退缩反射（NWR）的影响，以此作为量化麻醉效能的一种方法。
7匹健康成年设得兰矮种马。
测定每匹小马的异氟烷个体MAC（iMAC）。然后，评估在0.85、0.95和1.05 iMAC下给予异氟烷对NWR的影响。在每个浓度下，通过刺激指神经，以肌电图方式确定指总伸肌和三角肌的NWR阈值；给予额外的电刺激（3、5、10、20、30和40 mA），并记录和分析诱发活动。麻醉结束后，评估站立小马的NWR阈值。
异氟烷的平均±标准差MAC为1.0±0.2%。麻醉期间，两块肌肉的NWR阈值均以浓度依赖性方式显著升高，而在清醒小马中则降低。在麻醉的小马中，三角肌的阈值显著高于指总伸肌的阈值。在每个测试的iMAC下，随着刺激强度从3 mA增加到40 mA，两块肌肉的反射反应幅度均增加。检测到诱发反射的浓度依赖性抑制，刺激-反应函数斜率降低。
通过评估NWR可检测到用浓度约为1.0 MAC的异氟烷麻醉的小马中麻醉诱导的感觉运动处理变化。该方法将允许比较吸入麻醉药或麻醉组合对马属动物脊髓处理的影响。
