Does Thoracic Epidural Anesthesia Affect Gut Mucosal Blood Flow in Rats? Sielenkämper et al.(page 844)

Thoracic epidural anesthesia has been shown to attenuate surgery-related injury to the gastrointestinal system, possibly by preventing a decrease in gastric intramucosal pH, a surrogate marker for adequate intestinal perfusion. After equipping 19 rats with epidural catheters, Sielenkamper et al.  randomized the animals to receive epidural infusion of either 20 μl bupivacaine, 0.4%, or normal saline. Videomicroscopy of the ileal mucosa was performed before and after epidural infusion, and the images captured for off-line analysis of microvascular blood flow.

Epidural bupivacaine infusion induced a complete block of hind limb motility in conscious rats in less than 2 min. In all animals, motility was restored within 18–22 min after infusion. During intravital microscopy, the epidural infusion of bupivacaine in anesthetized rats resulted in a decrease in mean arterial pressure (MAP) from 108 ± 9 to 62 ± 10 mmHg within 60 s. Video recordings to assess effects of epidural bupivacaine began after hemodynamics stabilized (approximately 1–4 min).

Epidural bupivacaine increased erythrocyte velocity (VRBC) in terminal arterioles. The total intercapillary area size (ICATOT) was unchanged, but for the group receiving thoracic epidural anesthesia, there was indication of a possible decrease (stop and go) blood flow in the villus microcirculation. The observed increase in gut mucosal blood flow, said the authors, was likely the result of sympathetic nerve blockade, followed by a beneficial interorgan or within-organ redistribution of blood flow.