Comparison of pulse pressure variation and end-diastolic volume index in an experimental model of hemorrhagic shock in the pig

Introduction

Different hemodynamic parameters, including static indicators of cardiac preload such as the end-diastolic volume index (EDVI) and dynamic parameters such as the pulse pressure variation (PPV) have been used in the decision-making process regarding volume expansion in critically ill patients. The objective of this study was to compare fluid resuscitation guided by either PPV or EDVI, after hemorrhagic shock.

Methods

Twenty anesthetized and mechanically ventilated pigs were randomly allocated into two groups: PPV and EDVI. Hemorrhagic shock was induced by removing blood to a target pressure of 40 mmHg and was maintained for 60 minutes. Parameters were measured at baseline, at the time of the shock (Shock0), 60 minutes after the shock (Shock60), immediately after resuscitation with hydroxyethyl starch 6% (130/0.4) (R0), and 1 hour (R60) and 2 hours (R120) after resuscitation. The endpoint of fluid replacement was to re-establish the baseline values of PPV or EDVI. Data were submitted to ANOVA for repeated measures followed by the Bonferroni test.

Results

The resuscitation solution volume was higher in the EDVI group when compared with PPV (EDVI = 1,305 ± 331 ml and PPV = 965 ± 245 ml; P < 0.05). The time required to reach the endpoint was also different between groups (PPV = 8.8 ± 1.3 min and EDV = 24.8 ± 4.7 min). The cardiac index decreased after shock (Shock0 and Shock60, P < 0.01) and increased after resuscitation (R0, P < 0.01) in the PPV group. In the EDVI group, the cardiac index decreased at Shock0 (P < 0.05) and increased during R0 and R60 (P < 0.05). The right atrial pressure and pulmonary artery wedge pressure decreased after shock in both groups (Shock0 and Shock60, P < 0.05), reaching baseline values after resuscitation. Oxygen delivery decreased after shock in both groups (Shock0 and Shock60, P < 0.001), recovered the baseline value at R0 in both groups, but decreased at R60 and R120 in group PPV and at R120 in the EDVI group. Lactate increased at Shock60 in both groups and remained high at R0 in the PPV group and at R0 and R60 in the EDVI group.

Conclusion

After hemorrhagic shock, the resuscitation to an established endpoint was quicker and required less fluid with PPV when compared with EDVI.