Hector Rachel C, Rezende Marlis L, Mama Khursheed R, Steffey Eugene P, Knych Heather K, Hess Ann M, Honkavaara Juhana M, Raekallio Marja R, Vainio Outi M
Department of Clinical Sciences, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, CO, USA.
Department of Clinical Sciences, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, CO, USA.
Vet Anaesth Analg. 2017 Jul;44(4):755-765. doi: 10.1016/j.vaa.2016.12.058. Epub 2017 Mar 4.
To determine the effects of low and high dose infusions of dexmedetomidine and a peripheral α-adrenoceptor antagonist, MK-467, on sevoflurane minimum alveolar concentration (MAC) in dogs.
Crossover experimental study.
Six healthy, adult Beagle dogs weighing 12.6±0.9 kg (mean±standard deviation).
Dogs were anesthetized with sevoflurane in oxygen. After a 60-minute instrumentation and equilibration period, the MAC of sevoflurane was determined in triplicate using the tail clamp technique. PaCO and temperature were maintained at 40±5 mmHg (5.3±0.7 kPa) and 38±0.5 ºC, respectively. After baseline MAC determination, dogs were administered two incremental loading and infusion doses of either dexmedetomidine (1.5 μg kg then 1.5 μg kg hour and 4.5 μg kg then 4.5 μg kg hour) or MK-467 (90 μg kg then 90 μg kg hour and 180 μg kg then 180 μg kg hour); loading doses were administered over 10 minutes. MAC was redetermined in duplicate starting 30 minutes after the start of drug administration at each dose. End-tidal sevoflurane concentrations were corrected for calibration and adjusted to sea level. A repeated-measures analysis was performed and comparisons between doses were conducted using Tukey's method. Statistical significance was considered at p<0.05.
Sevoflurane MAC decreased significantly from 1.86±0.3% to 1.04±0.1% and 0.57±0.1% with incremental doses of dexmedetomidine. Sevoflurane MAC significantly increased with high dose MK-467, from 1.93±0.3% to 2.29±0.5%.
Dexmedetomidine caused a dose-dependent decrease in sevoflurane MAC, whereas MK-467 caused an increase in MAC at the higher infusion dose. Further studies evaluating the combined effects of dexmedetomidine and MK-467 on MAC and cardiovascular function may elucidate potential benefits of the addition of a peripheral α-adrenergic antagonist to inhalation anesthesia in dogs.
确定低剂量和高剂量右美托咪定以及外周α-肾上腺素能受体拮抗剂MK-467静脉输注对犬七氟醚最低肺泡有效浓度（MAC）的影响。
交叉实验研究。
6只健康成年比格犬，体重12.6±0.9千克（均值±标准差）。
犬采用七氟醚-氧气麻醉。在60分钟的仪器安装和平衡期后，使用尾夹法对七氟醚的MAC进行三次测定。动脉血二氧化碳分压（PaCO）和体温分别维持在40±5毫米汞柱（5.3±0.7千帕）和38±0.5℃。在测定基线MAC后，给犬静脉输注递增负荷剂量和维持剂量的右美托咪定（1.5微克/千克然后1.5微克/千克·小时以及4.5微克/千克然后4.5微克/千克·小时）或MK-467（90微克/千克然后90微克/千克·小时以及180微克/千克然后180微克/千克·小时）；负荷剂量在10分钟内输注完毕。在每个剂量开始给药30分钟后，再次重复测定MAC两次。呼气末七氟醚浓度经校准校正并换算至海平面高度。采用重复测量分析，并使用Tukey法进行剂量间比较。P<0.05认为具有统计学意义。
随着右美托咪定剂量递增，七氟醚MAC从1.86±0.3%显著降至1.04±0.1%和0.57±0.1%。高剂量MK-467使七氟醚MAC显著升高，从1.93±0.3%升至2.29±0.5%。
右美托咪定使七氟醚MAC呈剂量依赖性降低，而MK-467在较高输注剂量时使MAC升高。进一步评估右美托咪定和MK-467联合应用对MAC及心血管功能影响的研究，可能会阐明在犬吸入麻醉中添加外周α-肾上腺素能拮抗剂的潜在益处。
