Prediction of volume response under open-chest conditions during coronary artery bypass surgery

INTRODUCTION Adequate fluid loading is the first step of hemodynamic optimization in cardiac patients undergoing surgery. Neither a clinical approach alone nor conventional parameters like central venous pressure (CVP) and pulmonary capillary wedge pressure (PCWP) are thought to be sufficient for recognizing fluid deficiency or overload. The aim of this study was to evaluate the suitability of CVP, PCWP, global end-diastolic volume index (GEDVI), pulse pressure variation (PPV), and stroke volume variation (SVV) for predicting changes in the cardiac index (CI) and stroke volume index (SVI) after sternotomy. METHODS In 40 patients, CVP, PCWP, GEDVI, PPV, SVV, and the CI were measured at two points of time. One measurement was performed after inducing anesthesia and one after sternotomy. RESULTS A significant increase in heart rate, CI, and GEDVI was observed during the study period. CVP, SVV, and PPV decreased significantly. There were no significant correlations between CVP and PCWP and changes in CI. In contrast, GEDVI, SVV, and PPV significantly correlated with CI changes. Only relative changes of GEDVI, SVV, and PPV predicted changes in SVI. CONCLUSION During cardiac surgery and especially after sternotomy, CVP and PCWP are not suitable for monitoring fluid status. Direct volume measurement like GEDVI and dynamic volume responsive measurements like SVV and PPV may be more suitable for monitoring the volume status of patients, particularly under open-chest conditions.