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Objective: To investigate whether sympathetic blockade by means of thoracic epidural anaesthesia (TEA) increases intestinal perfusion during normotensive endotoxaemia., Design: A prospective, randomised and controlled animal study., Setting: Animal laboratory in a university hospital., Subjects: Sprague-Dawley male rats., Interventions: The rats were anaesthetised with urethane and ketamine, mechanically ventilated and haemodynamically monitored. Lidocaine or saline were infused continuously via thoracic epidural catheters followed by a continuous intravenous infusion of Escherichia coli lipopolysaccharide (1.5 mg/kg per h). Densities of perfused and non-perfused capillaries (i.e., with and without erythrocyte perfusion, respectively) as well as erythrocyte velocity in both the mucosa and the muscularis of the terminal ileum were determined using intravital microscopy., Measurements and Results: Measurements were performed at baseline, after 30 min of epidural infusion as well as after 60 and 120 min of lipopolysaccharide infusion. In animals receiving TEA, mean arterial pressure and heart rate were significantly reduced throughout the experiment. In the muscularis the endotoxaemia-induced increase in non-perfused capillaries was absent with epidural lidocaine (0 [0/0] versus 39 [36/137] cm(-1), median [25(th)/75(th) percentile]), whereas in the mucosa perfused capillary density declined to a greater extent than in controls (-47 [-53/-23]%) versus -19 [-34/+10]%, p<0.05). Erythrocyte velocity decreased with endotoxaemia and was not influenced by epidural lidocaine., Conclusions: Microvascular perfusion data during endotoxaemia show a redistribution of blood flow towards the mucosa. TEA seems to impede this redistribution resulting in improved muscularis and worsened mucosal microvascular perfusion.

Background: During hemorrhagic hypotension, sympathetic vasoconstriction crucially contributes to gut mucosal damage. Sympathetic blockade by thoracic epidural anesthesia has been shown to increase mucosal microvascular perfusion and to improve survival after severe hemorrhage in laboratory animals. This study investigates the effects of thoracic epidural anesthesia on intestinal microvascular perfusion during hemorrhagic hypotension in rats., Methods: In 32 anesthetized Sprague-Dawley rats either lidocaine 2% (thoracic epidural anesthesia) or normal saline (control) was infused via thoracic epidural catheters. Hemorrhagic hypotension (mean arterial pressure 30 mmHg for 60 min) was induced by withdrawal of blood, which was subsequently retransfused for resuscitation. Functional capillary density and erythrocyte velocity in the mucosa and muscularis were determined by intravital microscopy. Leukocyte-endothelium interaction was studied in postcapillary venules and sympathetic nerve fibers of the intestinal wall were identified by immunohistochemistry., Results: During hypotension functional capillary density was significantly (P < 0.001) lower in the muscularis of the control group (median [25/75 percentile]: -46.5% [-59.6/-20.8%] change from baseline) as compared with animals that received thoracic epidural anesthesia (-6.1% [-13.4/1.1%]). There were no differences in erythrocyte velocity between groups throughout the experiment. Leukocyte rolling increased significantly (P < 0.001) after resuscitation in control (12 [6/15] vs. baseline 2.5 [1/8]) but not in thoracic epidural anesthesia (4 [2.3/7] vs. baseline: 5 [3/15.5]). Sympathetic nerve fibers were identified in the muscularis and submucosa but not in the mucosa., Conclusions: During hemorrhagic hypotension and after resuscitation, thoracic epidural anesthesia has beneficial effects on intestinal microvascular perfusion. Because of blockade of sympathetic nerves, thoracic epidural anesthesia prevents perfusion impairment of the muscularis during hypotension and attenuates leukocyte rolling after resuscitation.