TREATMENT WITH A PLATELET-ACTIVATING FACTOR ANTAGONIST HAS LITTLE PROTECTIVE EFFECTS DURING ENDOTOXIC SHOCK IN THE DOG

Platelet-activating factor (PAF) is a potent vasoactive and inflammatory lipid mediator which has been implicated in the hemodynamic alterations of endotoxemia and sepsis. Different PAF receptor antagonists have been shown to attenuate the systemic and pulmonary disturbances of sepsis, but they were generally administered before the injection of endotoxin and their effects have not been consistent. To examine the effects of BB-882, a novel potent PAF receptor antagonist, on general hemodynamics and regional flow distribution in a canine endotoxic shock model, 14 anesthetized and ventilated dogs received 2 mg/kg of Escherichia coli endotoxin intravenously (i.v.) followed by generous fluid resuscitation. Thirty minutes later, the dogs received either BB-882 (n = 7) as a continuous i.v. infusion with hourly increasing doses (2, 5, and 10 mg/kg.h, respectively) or a corresponding amount of saline (n = 7). The administration of BB-882 resulted in a dose-dependent reduction in cardiac output and an increase in systemic and pulmonary vascular resistance. Mesenteric and renal flow were not different from control values whereas femoral blood flow progressively decreased. Another group of 7 dogs received 5 mg/kg i.v. bolus of BB-882 30 min before endotoxin. Pretreatment significantly increased mesenteric blood flow by about 50% but did not show any significant hemodynamic effects. This study demonstrates that the administration of a PAF receptor antagonist following endotoxic shock in fluid resuscitated dogs does not offer significant hemodynamic benefit. Pretreatment with BB-882 at the dose used only enhanced mesenteric perfusion. These findings do not support beneficial effects of PAF receptor antagonists in septic shock.