Pulse pressure variation and stroke volume variation to predict fluid responsiveness in patients undergoing carotid endarterectomy

Abstract

Background: During carotid endarterectomy (CEA), hemodynamic stability and adequate fluid management are crucial to prevent perioperative cerebral stroke, myocardial infarction and hyperperfusion syndrome. Both pulse pressure variation (PPV) and stroke volume variation (SVV), dynamic preload indices derived from the arterial waveform, are increasingly advocated as predictors of fluid responsiveness in mechanically ventilated patients. The aim of this study was to evaluate the accuracy of PPV and SVV for predicting fluid responsiveness in patients undergoing CEA.

Methods: Twenty seven patients undergoing CEA were enrolled in this study. PPV, SVV and cardiac output (CO) were measured before and after fluid loading of 500 ml of hydroxyethyl starch solution. Fluid responsiveness was defined as an increase in CO ≥ 15%. The ability of PPV and SVV to predict fluid responsiveness was assessed using receiver operating characteristic (ROC) analysis.

Results: Both PPV and SVV measured before fluid loading are associated with changes in CO caused by fluid expansion. The ROC analysis showed that PPV and SVV predicted response to volume loading (area under the ROC curve = 0.854 and 0.841, respectively, P < 0.05). A PPV ≥ 9.5% identified responders (Rs) with a sensitivity of 71.4% and a specificity of 90.9%, and a SVV ≥ 7.5% identified Rs with a sensitivity of 92.9% and a specificity of 63.6%.

Conclusions: Both PPV and SVV values before volume loading are associated with increased CO in response to volume expansion. Therefore, PPV and SVV are useful predictors of fluid responsiveness in patients undergoing CEA.

Keywords: Arterial blood pressure; Cardiac output; Carotid endarterectomy; Fluid therapy; Stroke volume.

Fig. 1

Relationships between the percentage changes in cardiac output related to fluid loading and PPV before fluid loading (A), SVV before fluid loading (B). Spearman's correlation coefficients (ρ) for PPV and SVV were 0.480 and 0.435, respectively. PPV: pulse pressure variation, SVV: stoke volume variation.

Fig. 2

The PPV and SVV before and after fluid loading in the responders (A) and nonresponders (B). Each line delineates changes of raw values for PPV and SVV before and after PPV and SVV in each patient. Red dotted line represents mean values (SD) for PPV and SVV before and after fluid loading. The mean values (SD) for PPV and SVV before fluid loading were 13.8 (6.4) and 13.4 (5.4) and the mean values (SD) for PPV and SVV after fluid loading were 5.3 (3.6) and 5.9 (4.0) in responders. The mean values (SD) for PPV and SVV before fluid loading were 6.5 (2.5) and 7.5 (3.0) and the mean values (SD) for PPV and SVV after fluid loading were 5.5 (1.6) and 6.2 (2.6) in non-responders. PPV: pulse pressure variation, SVV: stoke volume variation.

Fig. 3

ROC curves comparing the ability of PPV and SVV before fluid loading to discriminate between responders and non-responders. ROC: receiver operating characteristic, PPV: pulse pressure variation, SVV: stoke volume variation.

Fig. 4

Dot diagram plot for (A) PPV and (B) SVV of responders (Rs) and non-responders (NRs). Each symbol represents individual values of PPV and SVV before fluid loading. Horizontal straight line represents the optimal threshold values in predicting fluid responsiveness. A PPV ≥ 9.5% identified Rs with a sensitivity of 71.4% and a specificity of 90.9%, and a SVV ≥ 7.5% identified Rs with a sensitivity of 92.9% and a specificity of 63.6%. PPV: pulse pressure variation, SVV: stoke volume variation.