Effects of dihydroergotamine on the feline cardiovascular response to intravenous infusion of live Escherichia coli bacteria.

A septic shock state was induced in cats by intravenous infusion of live Escherichia coli bacteria. Cats pretreated with an unspecific 5-HT blocker, dihydroergotamine (DHE), or with a specific 5-HT blocker, ketanserin, were compared with a series receiving bacteria without pretreatment. DHE pretreatment prevented the reduction in systemic arterial blood pressure found in the other series during the 2-hour period of septic shock. Pretreatment could not influence the increased vascular resistance in the pulmonary vascular bed or the early increase in pulmonary arterial blood pressure. Peripheral blood flow distribution was studied using radioactive labelled microspheres. Compared to bacteremia without pretreatment, the 5-HT blockers increased CNS blood flow and ketanserin also prevented the reduction in pancreatic blood flow. Gastric blood flow and gastric mucosal blood flow remained unchanged in all series as did the small intestinal total blood flow. Small intestinal mucosal blood flow, however, was reduced after 2 h of bacteremia. Microscopy revealed no gastric epithelial damage while the jejunal mucosa was characteristically damaged. There was no correlation between the changes in the small intestinal blood flow and the degree of mucosal damage, however, supporting the countercurrent theory for the pathogenesis of these lesions.