Endotoxemia alters splanchnic capacitance

The splanchnic circulation constitutes a major portion of the total capacit ance vasculature and may affect venous return and subsequently cardiac outp ut during low output states. This study assessed the effects of rapid (10 m u g/kg over 5 min) and slow (10 mu g/kg over 60 min) induction of endotoxin (Escherichia coli) shock on splanchnic blood volume in 8 farm swine. Blood volume was measured by using Tc-99m-labeled erythrocytes and radionuclide imaging. Baseline arterial pressure (MAP), central venous pressure (CVP), a nd liver, splenic, mesenteric and total splanchnic volumes were stable duri ng the 30-min baseline. Approximately 30 min after the rapid endotoxin infu sion, splenic volume decreased by 45%, whereas liver volume increased by 40 % and MAP decreased by 60% (P < 0.01). The reduction in splenic volume occu rred within 10 min of the endotoxin infusion, whereas liver volume changes occurred after MAP reduction. The slow endotoxin infusion also reduced sple nic volume by approximately 50% (P = 0.05), whereas MAP declined by 30% (P < 0.05). However, the slow endotoxin infusion lowered liver volume (P < 0.0 5). Mesenteric volume was unaffected by the fast or slow endotoxin infusion . Total splanchnic volume was unaffected by the fast infusion but decreased by 37% in the slow infusion group (P < 0.05). In summary, E. coli endotoxi n reduces splenic blood volume and increases liver blood volume after acute hypotension ensues. Endotoxin does not increase total splanchnic blood vol ume and may actually decrease total splanchnic volume in the absence of cir culatory collapse. This endotoxin shock model is not associated with blood volume pooling in the splanchnic capacitance circulation.