Sielenkämper A W, Eicker K, Van Aken H
Department of Anesthesiology and Intensive Care Medicine, Westfälische Wilhelms-Universität, Münster, Germany.
Anesthesiology. 2000 Sep;93(3):844-51. doi: 10.1097/00000542-200009000-00036.
Previous studies reported that thoracic epidural anesthesia (TEA) protected against a decrease in gastric intramucosal pH, suggesting that TEA increased gut mucosal perfusion. The current study examines the effects of TEA on ileal mucosa using intravital microscopy in anesthetized rats.
Nineteen rats were equipped with epidural catheters, with the tip placed at T7 through T9. Rats were anesthetized and mechanically ventilated. After midline abdominal incision, the ileum was prepared for intravital microscopy. Videomicroscopy on the ileal mucosa was performed before and after epidural infusion of 20 microliter of bupivacaine 0.4% (TEA group, n = 11 rats) or normal saline (control group, n = 8 rats). Microvascular blood flow in ileum mucosa was assessed offline using computerized image analysis.
Control rats exhibited unchanged mean arterial pressure and microvascular perfusion. During TEA, mean arterial pressure was decreased compared with the control group (93 +/- 10 vs. 105 +/- 9 mmHg; P < 0.05). Epidural bupivacaine increased red cell velocity in terminal arterioles from 888 +/- 202 to 1,215 +/- 268 micrometer/s (control, 793 +/- 250 to 741 +/- 195 micrometer/s; P < 0.001 between groups). Because arteriolar diameter was not affected, this increase in red cell velocity may represent an increase in arteriolar blood flow. Total intercapillary area (inversely related to perfused capillary density) was unchanged, but for the TEA group the difference between total intercapillary area and the intercapillary area calculated for continuously perfused capillaries was decreased compared with the control group (16 +/- 12 vs. 40 +/- 19%; P < 0.001), indicating a decrease in intermittent (stop-and-go) blood flow in the villus microcirculation.
Thoracic epidural anesthesia increased gut mucosal blood flow and reduced intermittent flow in the villus microcirculation in the presence of a decreased perfusion pressure.
先前的研究报道，胸段硬膜外麻醉（TEA）可防止胃黏膜内pH值下降，提示TEA可增加肠道黏膜灌注。本研究采用活体显微镜观察法，在麻醉大鼠中研究TEA对回肠黏膜的影响。
19只大鼠置入硬膜外导管，导管尖端置于T7至T9水平。大鼠麻醉后行机械通气。经腹部正中切口后，准备对回肠进行活体显微镜观察。在硬膜外注入20微升0.4%布比卡因（TEA组，n = 11只大鼠）或生理盐水（对照组，n = 8只大鼠）前后，对回肠黏膜进行视频显微镜观察。使用计算机图像分析离线评估回肠黏膜的微血管血流。
对照组大鼠平均动脉压和微血管灌注无变化。在TEA期间，与对照组相比平均动脉压降低（93±10 vs. 105±9 mmHg；P < 0.05）。硬膜外注入布比卡因使终末小动脉中的红细胞速度从888±202微米/秒增加至1215±268微米/秒（对照组为793±250至741±195微米/秒；组间P < 0.001）。由于小动脉直径未受影响，红细胞速度的增加可能代表小动脉血流增加。毛细血管总面积（与灌注毛细血管密度呈负相关）未变，但与对照组相比，TEA组毛细血管总面积与连续灌注毛细血管计算的毛细血管面积之间的差异减小（16±12 vs. 40±19%；P < 但与对照组相比，TEA组毛细血管总面积与连续灌注毛细血管计算的毛细血管面积之间的差异减小（16±12 vs. 40±19%；P < 0.001），表明绒毛微循环中间歇性（停停走走）血流减少。
在灌注压降低的情况下，胸段硬膜外麻醉可增加肠道黏膜血流并减少绒毛微循环中的间歇性血流。
