Valley M A, McKenzie A M, Bourke D L, Raja S N
United States Air Force Medical Corps, Wilford Hall USAF Medical Center, Department of Anesthesiology, Lackland AFB, TX 78236.
Reg Anesth. 1994 Jan-Feb;19(1):52-8.
The authors sought to define the effects of differing volumes of epidural test dose on skin perfusion, skin temperature, and reflex vasoconstriction to a maximal inspiration (inspiratory gasp vasoconstrictive response, IGVR).
With informed consent and Institutional Review Board approval, the authors studied 40 patients undergoing epidural anesthesia. Skin perfusion was monitored in glabrous skin on the foot using laser Doppler. Inspiratory gasp vasoconstrictive response and temperature measurements were obtained at 1-minute intervals. After a baseline period, 5 patients received 60 mg intravenous lidocaine HCl; 5 received 5 mL normal saline, via epidural catheter; and 30 patients received 50 mg lidocaine HCl and 20 mcg epinephrine in 2.5, 5.0, or 7.5 mL normal saline (10 patients each). Inspiratory gasp vasoconstrictive response was defined as the percent change in perfusion from baseline produced by an inspiratory gasp. Perfusion was normalized by expressing each patient's value as a percentage of the respective baseline value.
Significant increases in perfusion, of up to 169% of baseline, were seen 12 minutes after the test dose. Inspiratory gasp vasoconstrictive response showed significant changes from baseline in all test groups. The temperature change was insignificant. Control groups did not show perfusion or IGVR changes.
Skin perfusion and IGVR changed significantly after epidural test dose; the minimal effect of volume appears to be 5 mL of lidocaine-epinephrine solution; the presence of IGVR or perfusion changes, or both, are positive predictors of successful placement of the catheter into the epidural space; and temperature changes as observed here were not reliable predictors of proper placement of epidural catheters.
作者试图确定不同容量的硬膜外试验剂量对皮肤灌注、皮肤温度以及最大吸气时反射性血管收缩（吸气屏气血管收缩反应，IGVR）的影响。
在获得患者知情同意并经机构审查委员会批准后，作者对40例行硬膜外麻醉的患者进行了研究。使用激光多普勒仪监测足部无毛皮肤的皮肤灌注情况。每隔1分钟测量吸气屏气血管收缩反应和温度。在基线期后，5例患者静脉注射60mg盐酸利多卡因；5例通过硬膜外导管注射5ml生理盐水；30例患者分别接受2.5ml、5.0ml或7.5ml生理盐水中含50mg盐酸利多卡因和20μg肾上腺素（每组10例）。吸气屏气血管收缩反应定义为吸气屏气引起的灌注相对于基线的变化百分比。通过将每个患者的值表示为各自基线值的百分比来使灌注标准化。
试验剂量后12分钟，灌注显著增加，最高可达基线的169%。所有试验组的吸气屏气血管收缩反应均较基线有显著变化。温度变化不显著。对照组未出现灌注或IGVR变化。
硬膜外试验剂量后皮肤灌注和IGVR发生显著变化；容量的最小影响似乎为5ml利多卡因 - 肾上腺素溶液；IGVR或灌注变化，或两者同时存在，是导管成功置入硬膜外间隙的阳性预测指标；此处观察到的温度变化不是硬膜外导管正确置入的可靠预测指标。
