Percentage hematocrit variation (PHEVAR) index as a quality indicator of patient blood management in cardiac surgery.

Background: Severe hemodilution and perioperative bleeding are determinants of hematocrit (HCT) variations in cardiac surgery patients. These variations may be direct determinants of bad outcomes, and may trigger allogeneic blood product transfusions, which are associated with morbidity and mortality. The present study introduces the Percentage HEmatocrit VARiation (PHEVAR) index as a tool to assess the quality of patient blood management (PBM) and to possibly guide specific interventions.

Methods: Seven-hundred-thirteen adult cardiac surgery patients were included in a retrospective analysis. The PHEVAR index was assessed based on the HCT determination at six points in time, being represented by the area under the curve of the percentage HCT variation from baseline. The PHEVAR index was explored for association with operative mortality and other outcome measurements.

Results: The PHEVAR index was an independent predictor of operative mortality (odds ratio 1.015, 95% confidence interval 1.005-1.026), postoperative bleeding, length of mechanical ventilation; significantly higher values of PHEVAR were detected in patients with acute kidney injury, low cardiac output, and ventricular arrhythmias. Acute kidney injury was associated with a larger HCT variation during surgery; low cardiac output with a larger postoperative HCT variation; and ventricular arrhythmias with a larger preoperative HCT variation.

Conclusion: The PHEVAR index reflects HCT variations during 7 days of hospital stay in cardiac surgery patients, is associated with mortality and morbidity, and may be used as a quality index for PBM.