Differences in eicosanoid and cytokine production between injury/hemorrhage and bacteremic shock in the pig

Plasma concentrations of the eicosanoids leukotriene (LT)B4, LTC4D4E4, thromboxane (TX)A2 and prostaglandin (PG)I2, and tumor necrosis factor (TNF) were measured during acute bacteremic shock and injury/hemorrhage in two porcine models. As TXA2 and PGI2 are rapidly metabolized, we measured their stable metabolites TXB2 and 6-keto-PGF1 alpha. Bacteremic shock was induced by a graded infusion of Aeromonas hydrophila over 4 h. Injury/hemorrhage was produced by a 30 min, 30% total blood volume hemorrhage followed by a 30 min shock period and then reinfusion of shed blood. Nociceptive afferent nerve stimulation was applied to the brachial plexi to mimic the cardiovascular responses to tissue injury. There was no increase in eicosanoid or TNF levels in the injury/hemorrhage model. In sepsis there was an early peak in TNF (at 60 min) followed by peaks in LTB4 and LTC4D4E4 at 180 min. Both TXB2 and 6-keto-PGF1 alpha showed large increases at the end of the study but there was no evidence that they had reached a peak. These results suggest that the very early inflammatory response in bacteremic shock and injury/hemorrhagic shock may be quite different. This may have implications for any therapies aimed at reducing the incidence of multiple organ failure after either of these physiological insults.