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.