Myocardial O2 balance during fluid resuscitation in uncontrolled hemorrhage: computer model.

Abstract

To study myocardial oxygen balance during fluid resuscitation for uncontrolled hemorrhage. A computer simulation. A mathematical model of the cardio-vascular system was used to simulate uncontrolled hemorrhage with and without fluid replacement. The parameters of initial bleeding rates, fluid replacement, and time intervals were selected to approximate typical values encountered in an urban emergency medical services system. The model was used to calculate myocardial oxygen supply and demand, and the time from injury to myocardial oxygen deficit was calculated for each fluid regimen. The model predicts an exponential decline in bleeding rate when no fluids are administered. Optimal fluid infusion rate was predicted as a function of initial bleeding rate. The time to a negative myocardial oxygen balance was shorter when a fluid bolus (100 mL/min or more) was given compared with no fluid administration. For uncontrolled hemorrhage at initial bleeding rates of 100 mL/min or more, the time interval from injury to cardiac oxygen deficit is inversely related to the infusion rate. A detailed study of the myocardial oxygen balance provides a pathophysiologic rationale for fluid restriction in the initial management of uncontrolled hemorrhage.