Vainio O M, Bloor B C
Department of Anesthesiology, University of California, Los Angeles 90024-1778.
Am J Vet Res. 1994 Jul;55(7):1000-6.
Dexmedetomidine (DEX), an alpha 2-receptor agonist, is the pharmacologically active d-isomer of medetomidine, a compound used as a sedative in veterinary medicine. Isoflurane anesthetic requirement (minimum alveolar concentration; MAC), rectal temperature, and cardiorespiratory variables were studied in chronically instrumented Yucatan miniature swine during DEX (20 micrograms/kg of body weight)-induced changes in body temperature. All studies were performed at room temperature of 22 C. The DEX was given as a 2-minute infusion into the left atrium. Each pig was studied twice. For protocol 1, the core temperature of the pigs was maintained at (mean +/- SD) 38.2 +/- 0.5 C by use of a thermostatically controlled water blanket and a heating lamp. For protocol 2, the core temperature was not externally manipulated and it decreased from 38.2 +/- 0.4 C to 32.2 +/- 1.2 C during the more than 3 hours of the protocol. Control isoflurane MAC was 1.66 +/- 0.2% and was 1.74 +/- 0.3% for protocols 1 and 2, respectively; DEX decreased MAC by 34 and 44%, respectively. For protocol 1, reduction in MAC after DEX administration returned by 50 and 80% at 84 and 138 minutes, respectively. If rectal temperature was not maintained (eg, allowed to decrease), MAC was reduced by 57% at the same time as the return to 80% in the swine with maintained body temperature. Respiratory rate and minute ventilation were significantly higher in swine with maintained temperature. The PaCO2 was lower and, accordingly, pH was higher in these swine. Blood pressure and heart rate were not affected by temperature changes.
右美托咪定（DEX）是一种α2受体激动剂，是美托咪定的药理活性d-异构体，美托咪定是一种在兽医学中用作镇静剂的化合物。在长期植入仪器的尤卡坦小型猪中，研究了右美托咪定（20微克/千克体重）引起体温变化时的异氟烷麻醉需求（最低肺泡浓度；MAC）、直肠温度和心肺变量。所有研究均在22℃的室温下进行。右美托咪定通过向左心房输注2分钟给药。每头猪研究两次。方案1中，通过使用恒温控制的水毯和加热灯，将猪的核心温度维持在（平均±标准差）38.2±0.5℃。方案2中，不对外界核心温度进行控制，在方案进行的3个多小时内，核心温度从38.2±0.4℃降至32.2±1.2℃。对照异氟烷MAC为1.66±0.2%，方案1和方案2分别为1.74±0.3%；右美托咪定分别使MAC降低34%和44%。方案1中，给药后MAC的降低在84分钟和138分钟时分别恢复了50%和80%。如果不维持直肠温度（例如，任其降低），与体温维持正常的猪恢复到80%时相比，MAC同时降低了57%。体温维持正常的猪的呼吸频率和分钟通气量显著更高。这些猪的动脉血二氧化碳分压较低，相应地，pH值较高。血压和心率不受温度变化的影响。
