Use of an extracorporeal circuit to evaluate effects of intraluminal distention and decompression on the equine jejunum.

The research explores the effects of intraluminal distention and decompression on the jejunum (a part of the small intestine) of horses and its responses to various prokinetic substances.

Methodology

• To learn about the effects of distention (expansion due to pressure) and decompression on the jejunum, the researchers used jejunal segments harvested from five healthy horses. These segments were maintained outside the horse’s body in an extracorporeal circuit.
• The study subjected one segment from each horse to distention and decompression, while preserving another segment without distention. The expansion was exerted at a pressure of 25 cm H2O.
• The researchers measured variables including vascular resistance to assess the effects of distention and decompression, albumin clearance from blood to lumen for evaluating mucosal permeability, and the impact on the response of circular smooth muscle to three prokinetic agents.

Results

• Intestinal vascular resistance, which indicates the ease of blood flow through the vessels, was observed to increase during intraluminal distention, but it reverted to the baseline after decompression.
• The rate of albumin clearance increased following the distention, as compared with baseline and control conditions.
• Post-distention histologic assessment revealed minor to moderate damage (grade-1 and -2 lesions) to the mucosal villus—the small, finger-like projections that increase the intestine’s surface area for absorption.
• The study also found evidence of edema (fluid accumulation) and hemorrhage in the submucosa and muscular layers, as well as in the serosal surface—an outermost layer of the intestine. It was also observed that the distention led to loss of mesothelial cells, which line the serosal surface, and caused shrinkage of the villi and an increase in the submucosal volume.
• The researchers additionally observed a decreased contractile response (the ability of muscle tissue to contract) to the three prokinetic agents—cisapride, erythromycin, and metoclopramide—following distention.

Conclusions

• The researchers concluded that intraluminal distention of the jejunum followed by decompression results in an increase in mucosal permeability (the ease with which substances can pass through the mucosal barrier) and injury.
• Furthermore, the study suggests that following distention, the response of the jejunum to prokinetic substances, which are generally used to treat gastrointestinal disorders, actually decreases.