Influence of different states of hydration on injured tissue (bowel anastomosis) in a rat model

Sixty-three rats were divided into four groups according to the amount of IV fluid administered. To test the hypothesis that the swelling in inflammation, which is caused mainly by edema, is an autonomic process and is not influenced by the state of hydration of the experimental animal, we performed a standard jejunal anastomosis in a rat model and measured the amount of water (tritium) and sodium in the anastomosis and a corresponding length of jejunum without an anastomosis, which served as a control. In spite of availability or lack of a large amount of water and sodium, the proportion of these elements to dry tissue in the different groups remained the same. Because there was no statistically significant weight gain or loss between the different hydration groups and total body water also did not change significantly, we conclude that infusion of even very large or small amounts of fluid does not change the state of hydration of the animal. We postulate that, at least in the healthy rat, the kidneys are able to protect the body and the anastomosis from overhydration or dehydration, and the anastomosis/inflammation itself is autonomic with regard to the state of hydration of the animal.