The effects of vasoactive mediator antagonists on endotoxic shock in dogs. I

Many vasoactive mediators have been implicated in causing or maintaining the hypotension of endotoxic shock. What has yet to be firmly established is the relative importance of each of these mediators in a given shock model. In a canine endotoxic shock model (LD100), we studied the effects of opiate and prostaglandin inhibition 60 min after endotoxin administration. After thiopental anesthesia, the animals were instrumented to measure various cardiovascular parameters. Endotoxic shock was induced by injecting E. coli endotoxin (0111:B4) (1 mg/kg i.v.). Drug intervention occurred 60 min after endotoxin administration. Naloxone (2 mg/kg i.v.) improved mean arterial pressure (MAP) transiently. A more significant increase of MAP (85% of preshock levels) was attained after ibuprofen (12.5 mg/kg i.v.) administration secondary to an increase in total peripheral resistance (TPR). All groups had 0% 24-hour survival. These data suggest that the endogenous opioids, presumably inhibited by naloxone, seem to contribute little to this lethal canine endotoxic shock model. By contrast, the prostanoids which are inhibited by ibuprofen appear to be more hemodynamically significant in this model.