The ability of PiCCO versus LiDCO variables to detect changes in cardiac index: a prospective clinical study

Both PiCCO and LiDCO can provide dynamic preload parameters, pulse pressure variation (PPV) and stroke volume variation (SVV). The PiCCO device also provides a measure of intrathoracic blood volume index (ITBVI). We investigated the agreement between SVV and PPV, as well as the reliability of LiDCO- and PiCCO-measured SVV, PPV and ITBVI, in detecting fluid responsiveness before and after fluid challenge (FC).

We performed a prospective clinical study in University Hospital ICU. Nine adult ICU patients with cardiovascular instability were enrolled in the study. All patients were sedated and mechanically ventilated with intermittent positive pressure ventilation. The PiCCO and LiDCO systems were both connected to each patient. The PiCCO pulse waveform system was joined by a 5-French (Fr) thermistor-tipped arterial catheter inserted into the femoral artery. LiDCO measurements were performed through radial artery pulse contour analysis. Fluid challenge was performed using a rapid infusion of 7 mL/kg of 6% hydroxyethylstarch over 30 min.

Measurements of CI, ITBVI, SVV, and PVV were made using both techniques before and after FC. Pre-FC cardiac index (CI) measurements were similar with both devices, although the reading was higher after FC with the PiCCO device (P<0.001). The correlation coefficient between PiCCO-CI and LiDCO-CI was 0.85 (95% CI: 0.69 to 0.93; P<0.001); for P-PPV and L-PPV, it was 0.74 (95% CI: 0.49 to 0.88; P<0.001). Only ITBV had a significant correlation with LiDCO-CI or PiCCO-CI.

We found a narrow bias but less accurate precision in cardiac index values measured by a radial artery-site LiDCO catheter and a femoral artery-site PiCCO catheter, with poor agreement between radial and femoral-derived SVV and PPV measurements. ITBVI proved to be the best predictor of fluid responsiveness. The SVV does not seem to be reliable for preload optimization in ICU patients.