Cardiac Output Monitoring during Off-Pump Coronary Artery Bypass Grafting

Objective: To evaluate and compare monitors of cardiac output during repositioning and stabilization of the heart for off-pump coronary artery bypass (OPCAB) surgery. Design: Prospective, observational, clinical study. Setting: University teaching hospital. Participants: Consecutive patients scheduled to undergo elective OPCAB (n = 19). Interventions: Monitoring, induction, and anesthesia followed a routine protocol for coronary artery bypass patients. This included the use of transesophageal echocardiography (TEE) and pulmonary artery catheter placement. Measurements and Main Results: After positioning and stabilization for OPCAB surgery, the changes in descending aortic flow velocity (VTI) times heart rate (HR) and the mixed venous oxygen saturation (SvO₂) could be used to predict the changes in thermodilution cardiac output (TDCO) using the following model: ΔTDCO _(calc) = -13.15 + 0.35 (ΔVTI*HR) + 0.61 (ΔSvO ₂) where Δ indicates the percentage change from baseline values. The changes in mean arterial pressure, mean pulmonary artery pressure, and continuous cardiac output did not correlate with the changes in TDCO. Conclusion: The use of the VTI*HR, as determined by TEE, in addition to the SvO₂ can strengthen clinical decision making during repositioning and stabilization of the heart during OPCAB. Changes in the VTI*HR and SvO₂ can be used as surrogate markers for changes in CO during OPCAB surgery.