Lichtenstein S V, el-Dalati H, Panos A, Rice T W, Salerno T A
J Surg Res. 1987 Feb;42(2):166-78. doi: 10.1016/0022-4804(87)90115-6.
Although the peripheral vascular effects of epinephrine have been characterized in animal models, similar studies have not been carried out in man. To determine the vascular effects of epinephrine the systemic circuit must be conceptually and surgically opened to allow for independent control of flow and pressure. This unique situation exists in man only while on total cardiopulmonary bypass with an external reservoir and pump interposed between the right atrium and the aorta. Under these conditions, peripheral vascular compliance, arteriolar and venous resistance, and the systemic time constant (a measure of the drainage characteristics of the vascular bed, in units of time) can be determined directly. Nine anesthetized patients undergoing normothermic cardiopulmonary bypass were studied before and during epinephrine infusion (5 micrograms/kg/min) after the aorta was cross-clamped and the heart had been isolated from the rest of the peripheral circulation. At constant blood flow epinephrine infusion increased blood pressure and reservoir volume (effectively decreasing blood volume) by an average of 360 ml. Although systemic vascular compliance decreased (due to venoconstriction), resistance to venous return decreased. Analysis of transient blood volume changes after a step change in right atrial pressure at constant blood flow revealed that blood was effectively draining from two vascular compartments with different time constants, as previously demonstrated in animal experiments. Epinephrine caused redistribution of blood flow away from the compartment with the longest time constant by constricting the arterioles leading to it. This accounts for the major increase in venous return and is almost entirely the mechanism of increased cardiac output in the normal individual after its administration, independent of its effects on the heart. In an attempt to localize the long and short time constant vascular compartments, three normal volunteers were studied. Thallium-201 whole body imaging at rest and after maximal treadmill exercise showed redistribution of blood flow away from the mesenteric bed and towards the muscle compartments. Although two similar compartment models of the circulation have been suggested by others, to our knowledge this type of analysis has not been carried out in man.
尽管肾上腺素对周围血管的作用已在动物模型中得到描述，但类似的研究尚未在人体中进行。为了确定肾上腺素对血管的作用，必须在概念上和手术上打开体循环，以便独立控制血流和压力。这种独特的情况仅在人体进行全心肺转流时存在，此时在右心房和主动脉之间插入一个外部储液器和泵。在这些条件下，可以直接测定周围血管顺应性、小动脉和静脉阻力以及体循环时间常数（以时间为单位衡量血管床引流特性的指标）。对9名在常温心肺转流下行手术的麻醉患者进行了研究，在主动脉交叉阻断且心脏与外周循环其余部分隔离后，于肾上腺素输注前（5微克/千克/分钟）和输注过程中进行观察。在恒定血流情况下，肾上腺素输注使血压升高，储液器容积增加（有效减少血容量），平均增加360毫升。尽管体循环血管顺应性降低（由于静脉收缩），但静脉回流阻力降低。在恒定血流下右心房压力发生阶跃变化后，对瞬时血容量变化进行分析发现，血液有效地从两个具有不同时间常数的血管腔室中流出，正如先前在动物实验中所证明的那样。肾上腺素通过收缩通向时间常数最长的腔室的小动脉，使血流从该腔室重新分布。这解释了静脉回流的主要增加，并且几乎完全是正常个体给药后心输出量增加的机制，与它对心脏的作用无关。为了试图确定长时间常数和短时间常数的血管腔室，对3名正常志愿者进行了研究。静息和最大量跑步机运动后用铊-201进行全身成像显示，血流从肠系膜床重新分布到肌肉腔室。尽管其他人曾提出过两种类似的循环腔室模型，但据我们所知，这种类型的分析尚未在人体中进行。
