In 24 patients subjected to cardio-pulmonary bypass (CPB) operation, changes in colloid oncotic pressure (COP), cardiac index (CI), respiratory index (RI), and pulmonary capillary wedge pressure (PCWP) were measured within a 48 hour period. The patients were divided into two groups according to dose levels of catecholamine. In 18 patients received small catecholamine doses, a stable hemodynamic and respiratory status were maintained. However, 6 patients received catecholamine doses of more than 15 micrograms/kg/min exhibited low COP, low CI, high RI and high PCWP. In this study we designed a new hemodynamic diagram using COP-PCWP and CI as parameters of the cardiac function. We consider that these parameters are more suitable than Forrester's parameters to evaluate the patient's condition before and after open heart surgery.