Shiga M, Nishina K, Mikawa K, Uesugi T, Maekawa N, Obara H
Department of Anesthesiology, Kobe Children's Hospital, Kobe, Japan.
Anesthesiology. 2000 Oct;93(4):954-8. doi: 10.1097/00000542-200010000-00013.
Caudal epidural anesthesia is often used as an adjunct to general anesthesia and for postoperative pain relief in children. In anesthetized children, epinephrine and isoproterenol are reliable indicators to detect accidental intravascular injection of a test dose. Oral clonidine, a useful premedicant in pediatric anesthesia, modifies hemodynamic responses to sympathomimetics, including catecholamines. The aim of the current study was to determine whether oral clonidine premedication alters the efficacy of a simulated intravascular test dose containing epinephrine or isoproterenol in sevoflurane-anesthetized children.
One hundred twenty children (aged 1-7 yr) were randomly divided into six groups; control-saline, control-epinephrine, control-isoproterenol, clonidine-saline, clonidine-epinephrine, and clonidine-isoproterenol. The three clonidine groups received oral clonidine 4 microg/kg [DOSAGE ERROR CORRECTED] as premedication, whereas the three control groups did not receive any premedication. Anesthesia was maintained with sevoflurane at a level of 1.2 minimum alveolar concentration. After hemodynamics were stable, 0.1 ml/kg of 1% lidocaine containing epinephrine 0.5 mg/kg or isoproterenol 75 ng/kg was intravenously given to the two epinephrine or isoproterenol groups, respectively, to simulate intravascular injection of a test dose. The saline groups received saline alone instead of the test dose. Heart rate, blood pressure, and T-wave amplitude of electrocardiogram were recorded before and after administration of study drugs for subsequent analysis.
Test solution containing epinephrine increased heart rate, systolic blood pressure, and T-wave amplitude. Oral clonidine had no effect on elevation of these variables in response to epinephrine. The isoproterenol-containing test dose produced a prominent increase in heart rate and a less pronounced increase in systolic blood pressure and T-wave amplitude. Oral clonidine also failed to modify isoproterenol-induced hemodynamic and T-wave changes. Calculated sensitivity and specificity of epinephrine or isoproterenol were all 100% based on a new heart rate criterion (positive if >/= 10 beats/min) and were unaltered by oral clonidine premedication.
Epinephrine or isoproterenol is a reliable marker to detect accidental intravascular injection of a test dose with 100% sensitivity and specificity based on a new heart rate criterion in sevoflurane-anesthetized children. These data suggest that oral clonidine premedication does not alter the efficacy of a simulated epidural test dose containing epinephrine or isoproterenol.
骶管硬膜外麻醉常用于小儿全身麻醉辅助及术后镇痛。在麻醉小儿中，肾上腺素和异丙肾上腺素是检测试验剂量意外血管内注射的可靠指标。口服可乐定是小儿麻醉中一种有用的术前用药，可改变对包括儿茶酚胺在内的拟交感神经药的血流动力学反应。本研究的目的是确定口服可乐定术前用药是否会改变含肾上腺素或异丙肾上腺素的模拟血管内试验剂量在七氟烷麻醉小儿中的效果。
120例1至7岁儿童随机分为六组：对照组-生理盐水、对照组-肾上腺素、对照组-异丙肾上腺素、可乐定-生理盐水、可乐定-肾上腺素和可乐定-异丙肾上腺素。三个可乐定组接受口服可乐定4μg/kg[剂量错误已纠正]作为术前用药，而三个对照组未接受任何术前用药。用七氟烷维持麻醉，浓度为1.2最低肺泡浓度。血流动力学稳定后，分别向两个肾上腺素或异丙肾上腺素组静脉注射0.1ml/kg含肾上腺素0.5mg/kg或异丙肾上腺素75ng/kg的1%利多卡因，以模拟试验剂量的血管内注射。生理盐水组仅接受生理盐水而非试验剂量。记录给药前后的心率、血压和心电图T波振幅，用于后续分析。
含肾上腺素的试验溶液可增加心率、收缩压和T波振幅。口服可乐定对肾上腺素引起的这些变量升高无影响。含异丙肾上腺素的试验剂量使心率显著增加，收缩压和T波振幅增加不明显。口服可乐定也未能改变异丙肾上腺素引起的血流动力学和T波变化。根据新的心率标准（心率增加≥10次/分钟为阳性）计算，肾上腺素或异丙肾上腺素的敏感性和特异性均为100%，且不受口服可乐定术前用药的影响。
根据新的心率标准，肾上腺素或异丙肾上腺素是检测七氟烷麻醉小儿试验剂量意外血管内注射的可靠标志物，敏感性和特异性均为100%。这些数据表明，口服可乐定术前用药不会改变含肾上腺素或异丙肾上腺素的模拟硬膜外试验剂量的效果。
