Thromboxane, prostacyclin, and the hemodynamic effects of graded bacteremic shock

This study investigates the interaction of thromboxane, prostacyclin, and the hemodynamic dysfunction of graded bacteremia. Arterial, venous, and pulmonary artery catheters were inserted into eight adult female pigs under barbiturate anesthesia. After a 60-min control period Aeromonas hydrophila (1.0 X 10(9)/ml) was infused intravenously at 0.2 ml/kg/hr, increasing gradually to 4.0 ml/kg/hr at 4 hr. Hemodynamic measurements, blood gases, and radioimmunoassay of thromboxane B2 (TxB) and prostaglandin 6-keto-F1 (PGI) were performed during the control period, at 10, 20, 30, 45, 60, 75, and 90 min of bacteremia and at 30-min intervals thereafter. During the bacterial infusion, cardiac index (CI), mean arterial pressure (MAP), paO2, pvO2, stroke volume (SV), and left ventricular stroke work (LVSW) decreased significantly, and pulmonary vascular resistance (PVR), pulmonary artery pressure (PAP), and intrapulmonary shunt (Qs/Qt) increased significantly. TxB was significantly increased at 30 min and remained elevated thereafter. PGI did not rise above control levels until after 240 min of bacterial infusion. TxB cross-correlated most frequently with CI, PVR, SV, paO2, and Qs/Qt, changes in TxB preceding the other variables by 0-60 min. PGI cross-correlated significantly with MAP, LVSW, CI, paO2, and Qs/Qt, changes in PGI preceding MAP, LVSW, and CI by 0-60 min, but following paO2 and Qs/Qt by 30-60 min. TxB is increased early in graded bacteremia and appears related to cardiorespiratory dysfunction. PGI increases late in graded bacteremia, following the onset of respiratory failure, and may mediate the arterial hypotension of septic shock.