Endotoxemia and large intestinal blood flow in subhuman primates

The hemodynamic effects of Escherichia coli endotoxin (LD80) were measured in the large intestine of anesthetized Rhesus monkeys to determine whether this organ contributes to the pathogenesis of experimental shock. Inferior mesenteric arterial blood flow (IMF) was measured with an electromagnetic flowmeter. Pressures within the aorta (AP) and portal vein (PP) were recorded. Distribution of colon blood flow was measured with radioactive microspheres: Ce, Sr, and Cr were injected into the left heart. Reference blood samples were obtained from a femoral artery. Mean control IMF was 22.9 +/- 2.2 (SE) ml/min. Aortic pressure was 113 +/- 11 mm Hg, and PP was 6 +/- 1 mm Hg. Arterial blood pH was 7.43 +/- 0.02; pO2 and pCO2 were 93.4 and 37.1 mm Hg, respectively. All parameters were measured at hourly intervals for 4 hr. Neither IMF nor its distribution within the colon changed during the entire observation period. Aortic pressure fell to a low of 60 +/- 6 mm Hg (p less than 0.02) at 3 hr; PP, pO2 and pCO2 were unchanged by endotoxin. Arterial blood pH fell to 7.315 +/- 0.020 at 4 hr (p less than 0.01). These observations indicate that the colon is not a "target organ" of endotoxic shock in subhuman primates, despite considerable hypotension and metabolic disturbances subsequent to near lethal endotoxemia.