Effects of hemorrhage on intramural blood flow distribution, villous tissue osmolality and fluid and electrolyte transport in the cat small intestine.

The hemodynamic response in the parallel-coupled vascular sections of the cat small intestine were studied before, during and after a two hour period of hemorrhage (about 30 per cent of estimated blood volume). Fluid and electrolyte transport and villous tissue osmolality were also measured. Biopsies for histology were taken at the end of all experiments. The animals were divided in two groups, undamaged and damaged, according to the degree of mucosal damage observed. The hemodynamic reactions were investigated with a method that made it possible to study total intestinal, absorptive site ("villous"), nonabsorptive site ("crypt") and muscle layer blood flows. Total intestinal blood flow was lower in the damaged as compared to the undamaged group during hypovolemia. No difference in absorptive site blood flow was observed between the two groups during hypovolemia. Furthermore, no decrease of red blood cell flow in the "villi" was recorded in either group after hemorrhage. Consequently, mucosal lesions developed despite an unchanged oxygen transport capacity to the villi. The pathophysiology of the mucosal lesions is briefly discussed. Net fluid and sodium absorption was after hemorrhage increased in the undamaged group reflecting a decrease in the tissue to lumen transport of sodium. After retransfusion net fluid and sodium absorption returned to control. In the damaged group, however, net fluid and sodium absorption was decreased after hemorrhage. The increased rate of fluid and electrolyte transport observed in the undamaged small intestine after hemorrhage, is proposed to be an important mechanism for fluid replacement after hemorrhage.