A computer model for analysis of fluid resuscitation

Injuries involving massive blood loss, such as burns, combat wounds, and injuries resulting from car accidents, require fluid resuscitation. The risk involved in fluid therapy is overloading of the circulation, resulting in pulmonary edema which can lead to death. The risk of pulmonary edema may be eliminated by proper determination of maximal infusion volume and rate. Reabsorption of fluid from the extravascular compartment and infusion of fluid following blood loss results in reduction of the hematocrit. This is accompanied by an increase in the heart's preload and afterload. Coronary driving pressure and flow increase due to increased volume. However, because of the reduced hematocrit this increase in coronary flow may not be sufficient to compensate the myocardium, in terms of oxygen supply, for the increase in oxygen consumption. A model of the cardiovascular system, including an extravascular compartment, was designed to analyze the effects of fluid infusion on hemodynamic variables, cardiac oxygen balance, and the redistribution of fluid between intravascular and extravascular compartments. The results indicate that edema is not the only possible adverse effect of overloading the cardiovascular system with fluids. The simulation demonstrated that in certain cases the heart's oxygen balance can become negative. Limiting the rate of infusion can reduce this risk.