Cardiopulmonary Bypass (CPB), a non-physiological intervention that maintains the blood circulation outside the body, brings about hemodynamic and biochemical changes, but these have not been elucidated in detail. Therefore, the aim of this study was a thorough examination of the changes in hemodynamic and biochemical parameters in patients at each stage of coronary bypass graft surgery (T1; before induction of anesthesia; T2: before CBP; T3: 5 min before placement of the cross clamp; T4: 5 min after removal of the cross clamp; T5: upon admission to intensive care; T6: 24 h post-operation). Pulmonary artery pressure, Mean Pulmonary Artery Pressure (MPAP), Central Venous Pressure (CVP), and Pulmonary Capillary Wedge Pressure (PCWP) were monitored and measured using a Swan-Ganz catheter introduced via the jugular vein at five of the six periods (not the period before anesthesia was induced). Mean Arterial Pressure (MAP) was monitored and measured through an arterial line. The blood lactate level was quantified during the same time periods using a blood gas device: it fell before the placement of the cross clamp (40 mmHg), but increased after the clamp was removed and rose to 80-100 mmHg at 24 h post-operation. The heart rate decreased after anesthesia  was normal in all other periods. CVP also declined slightly after removal of the cross clamp (T4), but remained in the normal range during the remaining periods. The MPAP and PCWP values were in the normal range throughout all steps during the bypass. Among the biochemical parameters, only lactate exhibited a noteworthy change. Lactate levels increased significantly in the T1-T3 period but gradually returned to normal in T4 (5 min after removal of the cross clamp). We contend that it is essential to measure hemodynamic parameters and lactate levels in order to track the physiological changes in patients during a successful CPB operation.