Effect of exogenous acid on the rat gastric mucosal microcirculation in hemorrhagic shock.

In vivo microscopy and histology were used to study the effect of exogenous acid (0.1 N HCl) on the rat corpus mucosal microcirculation and bleeding in hemorrhagic shock. Systemic blood pressure was reduced stepwise by bleeding. Mucosal blood flow showed a significant linear correlation with mean systemic blood pressure. The flow stopped in half of the rats at 25% of control blood pressure, but red blood cells were always present within the microvessels. In contrast, the topical application of 0.1 N HCl accelerated the decrease of blood flow with graded hypotension and caused progressive disappearance of the honeycomblike network of red blood cell-filled superficial mucosal microvessels. After retransfusion, mucosal bleeding occurred in the area in which the blood-filled microvessels had disappeared. Histology revealed that the bleeding extended from the middle of the depth of the mucosa and was associated with tissue necrosis. These results indicate that exogenous acid in hemorrhagic shock causes increased mucosal ischemia and tissue damage with bleeding on retransfusion.