Consistency of cardiac function index and global ejection fraction with global end-diastolic volume in patients with femoral central venous access for transpulmonary thermodilution: a prospective observational study.

Abstract

Global ejection fraction (GEF) and cardiac function index (CFI) are transpulmonary thermodilution (TPTD)-derived indices of the systolic function. Their validity relies on an accurate determination of the global end-diastolic volume (GEDV). Due to an overestimation of GEDV using a femoral central venous catheter (CVC) a correction formula for indexed GEDV (GEDVI) has been implemented in the latest PiCCO™-algorithm. However, a recent study demonstrated that correction for femoral CVC does not pertain to pulmonary vascular permeability index PVPI, which is calculated of extravascular lung water EVLW and GEDV. Therefore, it was the aim of our study to evaluate, if GEF and CFI are corrected for femoral CVC. In ten adult ICU-patients with PiCCO™-monitoring, ten triplicate TPTDs were performed within 30h. 95 complete data sets were analyzed, if a GEDV corrected for CVC site was applied to derive CFI and GEF. Therefore, we compared displayed values CFIdisplayed and GEFdisplayed to CFIcalculated and GEFcalculated, which were calculated from displayed GEDV, cardiac output and stroke volume. GEDVcalculated derived from division of GEDVI by predicted body surface area did not substantially differ from GEDVdisplayed (1448±414ml vs. 1447±416ml), which suggests a correction of GEDV for CVC site. However, CFIdisplayed was significantly lower than CFIcalculated (3.8±1.6/min vs. 5.1±1. 8/min: p<0.001), suggesting that CFIdisplayed is based on an uncorrected GEDV. By contrast, GEFcalculated (23.1±8.7%) was not substantially different from GEFdisplayed (22.4±8.6%). Although GEDV and GEF are corrected for femoral CVC site, this does not apply to CFI. However, all indices derived from GEDV should be calculated consistently.