Adolphs J, Schmidt DK, Mousa SA et al. Thoracic Epidural Anesthesia Attenuates Hemorrhage-induced Impairment of Intestinal Perfusion in Rats. Anesthesiology 2003;99:685-92.

The authors used Sprague-Dawley rats with epidural catheters placed al L4 and threaded in to the T11/12 level. The rats were divided into 2 sets of 2 groups. Each set had a group that received 2% lidocaine for a T6-L4 blockade and the other (control) group received a corresponding amount of saline. On set of groups was used to examine the mucosa of the ileum and the other set the muscularis of the ileum.

After urethane and ketamine anesthesia was commenced, a portion of the terminal ileum was exteriorized and placed in a video microscopy apparatus. Either the muscularis or mucosa was examined. The epidurals were injected, hemodynamics were monitored, and the hypotension was induced by withdrawing blood to a mean of 30 mmHg. The small bowel was examined for functional capillaries (capillaries open and carrying blood), white blood cell mobility, pH changes, and presence of sympathetic nerves.

MAP decreased as expected in the animals receiving lidocaine both prior to blood withdrawal and 60 minutes after resuscitation. Heart rate was lower in the lidocaine groups during hypotension and after resuscitation. Hematocrit did not differ between the groups. Local anesthetic block helped to maintain the percentages of functional capillaries in the muscularis during hypotension. This corresponds with less acidosis seen in the groups receiving lidocaine after 60 minutes of hypotension (7.34 v 7.24, p<0.01). The lidocaine groups had lower numbers of rolling leukocytes. These rolling leukocytes are part of the reperfusion injury pathway. Immunohistochemistry showed that there is a wealth of sympathetic nerves in the muscularis, but none in the mucosa. Thoracic epidural anesthesia blocked impairment of capillary perfusion in the mucosa despite a MAP of 30 mmHg and decreased heart rate, prevented systemic acidemia and development of base deficit during 60 minutes of hypotension, and inhibits the increase in rolling leukocytes during hypotension and reperfusion. Implication: Thoracic epidural anesthesia may minimize the effects of the profound hemodynamic perturbations seen during significant blood loss. Further work must be done to extend this research to examine other organ function, but previous work on dogs has shown that thoracic epidural anesthesia aids in survival of dogs after hypotension induced by blood withdwal.1 1. Shibata K. Yamamoto Y. Murakami S. Effects of epidural anesthesia on cardiovascular response and survival in experimental hemorrhagic shock in dogs. Anesthesiology 1989;71(6)53-9. Reviewed by: Andrew Ochroch, University of Pennsylvania