Hemodynamics changes induced by volume expansion measured by PiCCO^® system: the post-expansion effect

Aim

Volume expansion is usually guided by central venous pressure (CVP) [1]. PiCCO^® system which evaluates intra thoracic blood volume (ITBV) may be a useful guide for volume expansion The aim of this study was, using a PiCCO^® system, to measure the changes induced by a volume expansion in cardiac index (CI), systolic index (SI), mean systemic arterial pressure (MSAP), CPV and ITBV.

Materials and methods

Eighteen patients with acute circulatory ditress syndrome were prospectively studied. All the patients were sedated and mechanically ventilated and received 50 or 100 ml (group 1: CVP > 14 and 14 = CVP = 8 respectively) or 200 ml (group2: CVP < 8 cmH₂O) of HEAfusine 6%^® over a 10 min period. Hemodynamics measurements were performed using a transpulmonary indicator dilution technique (PiCCO^® Pulsion, Munich) before (T0), after fluid administration (T10) and 10 min later (T20).

Results

The acute circulatory distress syndrome was due to septic shock (n = 15), cardiogenic shock (n = 2) and hypovolemic shock (n = 1). The Table shows the changes observed from the baseline values at T10 (T0-T10) and from the end of volume expansion to 10 min later (T10-T20) in each group.

Table

Discussion

In the 200 ml group, 10 min after the end of volume expansion, the increase in MSAP and CVP disappears, whereas ITBV, CI and SI increases remain unchanged and even shows for ITBV a trend toward increase. This suggest a post-expansion effect which is not observed on CVP values. In group 2 who had a higher baseline CVP and a lower volume expansion, the increases in MSAP, CVP, ITBV and SI observed at the end of volume expansion disappear 10 min later, suggesting the absence of a post-expansion effect when the baseline CVP is high and/or the volume infused is low.

Conclusion

ITBV measurement may be a useful guide for the evaluation of volume expansion and post-volume expansion effect when baseline CVP is low and/or volume expansion is 200 ml.