The standardized stroke work, which is derived from the left ventricular stroke work (LVSW) and the pulmonary capillary wedge pressure (WP), is presented as a convenient index for tracking changes in the overall cardiac function and relating these changes to other cardiorespiratory variables. This index and its response to whole blood transfusion were used to assess cardiac function in 102 critically ill patients with hemorrhagic or traumatic shock. Survivors had greater mean values of the standardized stroke work before, during, and after transfusion than did the nonsurvivors (p< 0.05). Moreover, the maximal change in standardized stroke work in response to transfusion was greater in survivors than in nonsurvivors (p< 0.05); this response was found to be dependent on the stage of shock.The experience of the authors with this index suggests that it is a useful way to follow changes in myocardial performance in critically ill patients over time, and in quantitating changes in myocardial function after whole blood transfusion or other forms of volume therapy.