Hemodynamic basis of the pain of chronic mesenteric ischemia.

Tonometry, a new technique to indirectly assess intestinal blood flow, was used to determine the hemodynamic changes produced by a simulated meal in animals with a fixed, decreased splanchnic blood flow. In experiments on 14 dogs, celiac artery and superior mesenteric artery blood flow was maintained at 50 percent of normal flow by occluders and flow probes, and tonometers were placed in the stomach and small bowel to measure intramural pH, a metabolic marker of intestinal perfusion. Intramural pH was determined at 100 percent and 50 percent splanchnic blood flow, at 50 percent flow after instillation of cream into the stomach, and again when cream was placed into the small bowel. Intestinal intramural pH decreased significantly when blood flow was decreased to 50 percent, as expected, but decreased significantly again when cream was placed in the stomach. The hemodynamic explanation of the decrease when cream was placed in the stomach is a steal from the intestinal to the gastric circulation stimulated by food in the stomach. Such a steal could explain the temporal nature of the pain experienced by patients with chronic mesenteric ischemia.