Cardiopulmonary and splanchnic blood flow during 48 hours of a continuous infusion of endotoxin in conscious pigs: a model of hyperdynamic shock.

Hyperdynamic shock can be modeled in pigs by chronic administration of a continuous, low-dose infusion of endotoxin. Lipopolysaccharide (LPS, E. coli 0111:B4, 80 ng/kg/min i.v.) initially resulted in a hypodynamic shock state with significant decreases in mean arterial pressure (112+/-3 mmHg at baseline to 94+/-4 mmHg at 8 h) and cardiac index (5.35+/-0.32 L/min/m2 at baseline to 4.07+/-0.32 L/min/m2 at 4 h). Eight hours after the initiation of the LPS infusion, cardiac index rose to above baseline values (5.82+/-0.4 L/min/m2 at 8 h) and remained elevated for the duration of the 48-h study (6.54+/-0.39 L/min/m2 at 48 h). Similarly, systemic vascular resistance fell significantly by 8 h (1640+/-100 dyne sec cm(-5) at baseline to 1239+/-80 dyne sec cm(-5) at 8 h) and remained decreased for the duration of the study. Blood flow in major abdominal vessels, including the left renal artery, the cranial mesenteric artery, and the portal vein, paralleled changes in the cardiac index. Serum concentrations of tumor necrosis factor were increased after 2 h of LPS infusion, but did not remain elevated above baseline concentrations for more than about 4 h despite continuous LPS challenge. Concentrations of tumor necrosis factor did not differ between arterial and portal venous samples. This model of hyperdynamic shock should be useful to assess potential therapies for septic shock.