Campagnol Daniela, Teixeira Neto Francisco J, Giordano Tatiana, Ferreira Tatiana H, Monteiro Eduardo R
Department of Veterinary Surgery and Anesthesiology, Faculdade de Medicina Veterinária e Zootecnia, Universidade Estadual Paulista (UNESP), Botucatu, São Paulo, Brazil.
Am J Vet Res. 2007 Dec;68(12):1308-18. doi: 10.2460/ajvr.68.12.1308.
Objective-To evaluate the effects of epidural administration of 3 doses of dexmedetomidine on isoflurane minimum alveolar concentration (MAC) and characterize changes in bispectral index (BIS) induced by nociceptive stimulation used for MAC determination in dogs. Animals-6 adult dogs. Procedures-Isoflurane-anesthetized dogs received physiologic saline (0.9% NaCl) solution (control treatment) or dexmedetomidine (1.5 [DEX1.5], 3.0 [DEX3], or 6.0 [DEX6] mug/kg) epidurally in a crossover study. Isoflurane MAC (determined by use of electrical nociceptive stimulation of the hind limb) was targeted to be accomplished at 2 and 4.5 hours. Changes in BIS attributable to nociceptive stimulation and cardiopulmonary data were recorded at each MAC determination. Results-With the control treatment, mean +/- SD MAC values did not change over time (1.57 +/- 0.23% and 1.55 +/- 0.25% at 2 and 4.5 hours, respectively). Compared with the control treatment, MAC was significantly lower at 2 hours (13% reduction) but not at 4.5 hours (7% reduction) in DEX1.5-treated dogs and significantly lower at 2 hours (29% reduction) and 4.5 hours (13% reduction) in DEX3-treated dogs. The DEX6 treatment yielded the greatest MAC reduction (31% and 22% at 2 and 4.5 hours, respectively). During all treatments, noxious stimulation increased BIS; but changes in BIS were correlated with increases in electromyographic activity. Conclusions and Clinical Relevance-In dogs, epidural administration of dexmedetomidine resulted in dose-dependent decreases in isoflurane MAC and that effect decreased over time. Changes in BIS during MAC determinations may not represent increased awareness because of the possible interference of electromyographic activity.
目的——评估硬膜外给予3种剂量右美托咪定对异氟烷最低肺泡浓度（MAC）的影响，并描述用于测定犬MAC的伤害性刺激所诱发的脑电双频指数（BIS）变化。动物——6只成年犬。程序——在一项交叉研究中，异氟烷麻醉的犬接受生理盐水（0.9%氯化钠）溶液（对照处理）或硬膜外给予右美托咪定（1.5 [DEX1.5]、3.0 [DEX3]或6.0 [DEX6] μg/kg）。异氟烷MAC（通过对后肢进行电伤害性刺激来测定）的目标是在2小时和4.5小时达成。在每次测定MAC时记录由伤害性刺激引起的BIS变化以及心肺数据。结果——对照处理时，平均±标准差MAC值随时间未发生变化（2小时和4.5小时时分别为1.57±0.23%和1.55±0.25%）。与对照处理相比，DEX1.5处理的犬在第2小时MAC显著降低（降低13%），但在4.5小时未降低（降低7%）；DEX3处理的犬在2小时（降低29%）和4.5小时（降低13%）MAC均显著降低。DEX6处理使MAC降低幅度最大（2小时和4.5小时时分别降低31%和22%）。在所有处理过程中，伤害性刺激均使BIS升高；但BIS变化与肌电图活动增加相关。结论及临床意义——在犬中，硬膜外给予右美托咪定导致异氟烷MAC呈剂量依赖性降低，且该效应随时间减弱。在测定MAC期间BIS的变化可能并不代表意识增强，因为可能存在肌电图活动的干扰。
