Release of vasoactive intestinal peptide during hyperdynamic sepsis in dogs

Vasoactive intestinal peptide (VIP) is a potent vasodilator that has been reported to be a mediator of the hemodynamic changes in endotoxin-induced hypodynamic septic shock. We investigated the release of VIP in a hyperdynamic model of sepsis in awake, conscious dogs similar to that of sepsis in human beings. Sepsis was induced by intraperitoneal implantation of a fibrin clot containing live Escherichia coli (0.9 +/- 0.2 X 10(9) organisms per kilogram of body weight). All dogs developed hyperdynamic sepsis with increased cardiac output and decreased systemic vascular resistance. During the first 24 hours of sepsis, VIP was released without a concomitant decrease in blood pressure, suggesting that during septic shock it was released by a direct mechanism rather than as a result of hypotension. During peak VIP release (2 to 4 hours after induction of sepsis) no decreases in systemic vascular resistance or mean arterial pressure were observed. This suggests that mediators other than VIP may be responsible for the vasodilation observed during sepsis. The precise role of VIP during sepsis is therefore yet to be clarified.