Hemodynamic effects of dopamine, norepinephrine, and fluids in a dog model of sepsis.

To study how sepsis affects hemodynamic responses to catecholamines and fluids, either Escherichia coli-infected (septic, n = 8) or sterile (controls, n = 6) fibrin clots were implanted intraperitoneally into 2-yr-old beagles. Hemodynamics were measured at each of four doses of dopamine (0, 5, 10, and 20 micrograms.kg-1.min-1) and norepinephrine (0, 10, 20, and 40 micrograms.min-1), before and after infusion of fluid (Ringer 40 ml.kg-1). Septic animals had lower mean arterial pressure (MAP, P = 0.04), stroke volume index (SVI, P = 0.0001), and left ventricular (LV) ejection fraction (LVEF) (P = 0.0001) than controls. During this time, increasing doses of dopamine and norepinephrine produced corresponding increases (P < 0.001) in LVEF, SVI, and MAP. However, during sepsis, the ability of dopamine to increase MAP diminished, while its ability to increase LVEF and SVI was maintained. Conversely, the ability of norepinephrine to increase LVEF and SVI diminished, but its ability to increase MAP was maintained. During sepsis, fluids alone increased (P < 0.05) MAP, LVEF, SVI, and cardiac index (CI). Fluids with catecholamines also significantly increased (P < 0.05) MAP with only minimal increases in LVEF, SVI, and CI. These data demonstrate that during sepsis without catecholamines, fluids improve cardiac performance and systemic pressures, but with catecholamines, fluids have minimal effects on cardiac performance and augment MAP. Furthermore, during sepsis dopamine is more effective than norepinephrine in increasing LV performance, but norepinephrine is more effective than dopamine in increasing systemic pressures.