Study objectives: Stroke volume variation (SVV) and pulse pressure variation (PPV) determined by the PiCCOplus system (Pulsion Medical Systems; Munich, Germany) may be useful dynamic variables in guiding fluid therapy in patients receiving mechanical ventilation. However, with respect to the prediction of volume responsiveness, conflicting results for SVV have been published in cardiac surgery patients. The goal of this study was to reevaluate SVV in predicting volume responsiveness and to compare it with PPV.
Design: Prospective nonrandomized clinical investigation.
Setting: University-based cardiac surgery.
Patients: Forty patients with preserved left ventricular function undergoing elective off-pump coronary artery bypass grafting.
Interventions: Volume replacement therapy before surgery.
Measurements and results: Following induction of anesthesia, before and after volume replacement (6% hydroxyethyl starch solution, 10 mL/kg ideal body weight), hemodynamic measurements of stroke volume index (SVI), SVV, PPV, global end-diastolic volume index (GEDVI), central venous pressure (CVP) and pulmonary capillary wedge pressure (PCWP) were obtained. Also, left ventricular end-diastolic area index (LVEDAI) was assessed by transesophageal echocardiography. Prediction of ventricular performance was tested by calculating the area under the receiver operating characteristic (ROC) curves and by linear regression analysis; p < 0.05 was considered significant. All measured hemodynamic variables except heart rate changed significantly after fluid loading. GEDVI, CVP, PCWP, and LVEDAI increased, whereas SVV and PPV decreased. The best area under the ROC curve (AUC) was found for SVV (AUC = 0.823) and PPV (AUC = 0.808); the AUC for other preload indexes ranged from 0.493 to 0.636. A significant correlation with changes of SVI was observed for SVV (r = 0.606, p < 0.001) and PPV (r = 0.612, p < 0.001) only. SVV and PPV were closely related (r = 0.861, p < 0.001).
Conclusions: In contrast to standard preload indexes, SVV and PPV, comparably, showed a good performance in predicting fluid responsiveness in patients before off-pump coronary artery bypass grafting.