Cardiovascular function in shock. Responses to volume loading and isoproterenol infusion.

Hemodynamic responses to volume loading with infusion of dextran-40 and myocardial stimulation with isoproterenol in 23 patients in shock from hemorrhage, trauma, or sepsis, and 10 healthy controls were studied. Responses of the control were moderate to dextran and marked to isoproterenol. Shock patients were divided into three groups according to the response of the cardiac index to dextran-40: group I, > 50% increase; group II, 15 to 50% increase; group III, < 15% increase or a decrease. The central venous pressure of patients who responded to dextran (group I) generally rose moderately and that of those who failed to respond (group III) increased without improvement of cardiac index or stroke index, suggesting myocardial failure. Group II showed cardiac improvement at the expense of marked increase in venous pressure, suggesting relative cardiac insufficiency. Group I failed to respond to isoproterenol infusion, indicating that circulatory failure primarily resulted from failure of venous return. All group III patients responded markedly to isoproterenol. It is concluded that a significant number of patients in shock from hemorrhage, trauma, and sepsis exhibit signs of cardiac insufficiency. The ability of these hearts to respond to isoproterenol suggests that depletion or altered metabolism of endogenous catecholamines in part underlies this insufficiency. Furthermore, it is suggested that cardiac insufficiency may contribute to the death of a significant number of patients with severe hemorrhagic and septic shock.