Platelet Activating Factor Mediates Cardiopulmonary Dysfunction during Graded Bacteremic Shock

OBJECTIVE To determine whether or not platelet activating factor (PAF) is a necessary mediator of cardiovascular dysfunction during graded bacteremia, and to identify PAF interactions with eicosanoids and tumor necrosis factor-alpha (TNF-alpha). METHODS Seventeen anesthetized, hemodynamically monitored adult swine were studied for 4 hours in three groups. Group 1 (ANES, n = 5) were anesthesia controls; group 2 (septic control, SC, n = 6) received intravenous Aeromonas hydrophila (109/mL) at rates incrementally increased from 0.2 to 4.0 mL/kg/h; group 3 (WEB, n = 6) received the PAF receptor antagonist WEB 2086, 3.0 mg/kg intravenously, then A. hydrophila. Cardiopulmonary parameters and plasma thromboxane B2 (TXB2), prostaglandin 6-keto F1 alpha (PGI2), leukotriene B4 (LTB sub 4), leukotrienes C4 D4 E4 (LTC4 D4 E4), and TNF-alpha were measured hourly. Statistical analysis was carried out using two way analysis of variance (ANOVA) for repeated measurements, Dunnett's t test, and Student's t test, where appropriate. Statistical significance was determined at the 95% confidence interval. Values are presented as the mean +/- SEM. RESULTS Pulmonary arterial pressure, pulmonary capillary wedge pressure, central venous pressure heart rate, VO2 and O2 ER decreased significantly after WEB 2086 infusion, compared with SC, and mean arterial pressure, systemic vascular resistance index, stroke volume index, and left ventricular stroke work index increase. Arterial pH decreased significantly in SC animals, but was maintained at normal levels during bacteremia in the WEB group. Differences between WEB and SC for cardiac index, pulmonary vascular resistance index, right ventricular stroke work index, PaO2, SaO2, and PCO2, were not significant. The addition of WEB 2086 significantly decreased plasma levels of TXB2, PGI2, LTB4, and TNF-alpha compared with the SC group. LTC4 D sub 4 E4 was decreased in WEB compared with SC animals, in which LTC sub 4 D4 E4 increased during graded bacteremia. CONCLUSIONS PAF is necessary to the development of systemic vasodilation and hypotension, pulmonary hypertension, decreased stroke volume, metabolic acidosis, and increased oxygen uptake during graded bacteremia. PAF-induced eicosanoid and cytokine release may be involved.