Pulse pressure variation and volume responsiveness during acutely increased pulmonary artery pressure: an experimental study

Abstract

Introduction: We found that pulse pressure variation (PPV) did not predict volume responsiveness in patients with increased pulmonary artery pressure. This study tests the hypothesis that PPV does not predict fluid responsiveness during an endotoxin-induced acute increase in pulmonary artery pressure and right ventricular loading.

Methods: Pigs were subjected to endotoxemia (0.4 microg/kg/hour lipopolysaccharide), followed by volume expansion, subsequent hemorrhage (20% of estimated blood volume), retransfusion, and additional stepwise volume loading until cardiac output did not increase further (n = 5). A separate control group (n = 7) was subjected to bleeding, retransfusion, and volume expansion without endotoxemia. Systemic hemodynamics were measured at baseline and after each intervention, and PPV was calculated offline. Prediction of fluid-challenge-induced stroke volume increase by PPV was analyzed using receiver operating characteristic (ROC) curves.

Results: Sixty-eight volume challenges were performed in endotoxemic animals (22 before and 46 after hemorrhage), and 51 volume challenges in the controls. Endotoxin infusion resulted in an acute increase in pulmonary artery and central venous pressure and a decrease in stroke volume (all P < 0.05). In endotoxemia, 68% of volume challenges before hemorrhage increased the stroke volume by > 10%, but PPV did not predict fluid responsiveness (area under the ROC curve = 0.604, P = 0.461). After hemorrhage in endotoxemia, stroke volume increased in 48% and the predictive value of PPV improved (area under the ROC curve for PPV = 0.699, P = 0.021). In controls after hemorrhage, stroke volume increased in 67% of volume challenges and PPV was a predictor of fluid responsiveness (area under the ROC curve = 0.790, P = 0.001).

Conclusions: Fluid responsiveness cannot be predicted with PPV during acute pulmonary hypertension in porcine endotoxemia. Even following severe hemorrhage during endotoxemia, the predictive value of PPV is marginal.

Figure 1

Cardiac function curves showing fluid challenges in controls. Changes in stroke volume are shown in relation to concomitant changes in central venous pressure. Connected lines represent subsequent fluid challenges in individual animals.

Figure 2

Cardiac function curves showing fluid challenges in endotoxemia preceding hemorrhage. Changes in stroke volume are shown in relation to concomitant changes in central venous pressure. Connected lines represent subsequent fluid challenges in individual animals.

Figure 3

Cardiac function curves showing fluid challenges in endotoxemia after bleeding during retransfusion and volume expansion. Changes in stroke volume are shown in relation to concomitant changes in central venous pressure. Connected lines represent subsequent fluid challenges in individual animals.

Figure 4

Receiver operating characteristic curves for prediction of ≥10% increase in stroke volume by pulse pressure variation, showing all fluid challenges during endotoxemia. Solid line, all fluid challenges; dashed line, fluid challenges with concomitant increase in central venous pressure; thin solid line, line of identity.

Figure 5

Receiver operating characteristic curves for prediction of ≥10% increase in stroke volume by pulse pressure variation, showing fluid challenges in endotoxemia preceding hemorrhage. Solid line, all fluid challenges; dashed line, fluid challenges with concomitant increase in central venous pressure; thin solid line, line of identity.

Figure 6

Receiver operating characteristic curves for prediction of ≥10% increase in stroke volume by pulse pressure variation, showing fluid challenges in endotoxemia after bleeding during retransfusion and volume expansion. Solid line, all fluid challenges; dashed line, fluid challenges with concomitant increase in central venous pressure; thin solid line, line of identity.

Figure 7

Receiver operating characteristic curves for prediction of ≥10% increase in stroke volume by pulse pressure variation, showing fluid challenges in controls after bleeding during retransfusion and volume expansion. Solid line, all fluid challenges; dashed line, fluid challenges with concomitant increase in central venous pressure; thin solid line, line of identity.