Shibata K, Futagami A, Taki Y, Kobayashi T
Department of Anesthesiology and Intensive Care Medicine, Kanazawa University School of Medicine, Japan.
Anesthesiology. 1994 Dec;81(6):1454-60. doi: 10.1097/00000542-199412000-00021.
There is little information on the cardiovascular response to marked hypercapnia during epidural anesthesia (EA). Our objective was to assess the potential modifying effects of various levels of EA on this response.
We randomly assigned 48 mongrel dogs anesthetized with halothane (0.5%) to one of four groups: control (n = 12), receiving general anesthesia alone; lumbar (n = 12), also receiving lumbar EA; thoracic (n = 12), also receiving thoracic EA; and thoracolumbar (n = 12), also receiving thoracolumbar EA. During marked hypercapnia (mean arterial CO2 tension > 90 mmHg for 15 min), we measured hemodynamic parameters and plasma catecholamine concentrations in each group.
In the control condition, marked hypercapnia increased cardiac output, reduced systemic vascular resistance, modestly increased mean arterial blood pressure. Lumbar EA abolished the increase in cardiac output, and thoracic and thoracolumbar EA caused CO2 to depress the cardiac output and the mean arterial blood pressure during marked hypercapnia. The physiologic increase in circulating catecholamines during marked hypercapnia was abolished only in the thoracolumbar EA group.
We conclude that sympathetic blockade by EA modifies the cardiovascular response to marked hypercapnia in dogs. Although modest hypoventilation is often effective in treating hypotension during general anesthesia, the current results suggest that hypoventilation may be detrimental during the combination of EA and general anesthesia.
关于硬膜外麻醉（EA）期间对显著高碳酸血症的心血管反应的信息很少。我们的目的是评估不同水平的EA对这种反应的潜在调节作用。
我们将48只使用氟烷（0.5%）麻醉的杂种狗随机分为四组：对照组（n = 12），仅接受全身麻醉；腰部组（n = 12），同时接受腰部EA；胸部组（n = 12），同时接受胸部EA；胸腰部组（n = 12），同时接受胸腰部EA。在显著高碳酸血症期间（平均动脉血二氧化碳分压> 90 mmHg持续15分钟），我们测量了每组的血流动力学参数和血浆儿茶酚胺浓度。
在对照条件下，显著高碳酸血症增加了心输出量，降低了全身血管阻力，适度增加了平均动脉血压。腰部EA消除了心输出量的增加，胸部和胸腰部EA导致在显著高碳酸血症期间二氧化碳降低心输出量和平均动脉血压。仅在胸腰部EA组中，显著高碳酸血症期间循环儿茶酚胺的生理性增加被消除。
我们得出结论，EA引起的交感神经阻滞改变了狗对显著高碳酸血症的心血管反应。虽然适度通气不足通常可有效治疗全身麻醉期间的低血压，但目前的结果表明，在EA与全身麻醉联合使用期间，通气不足可能是有害的。
