Accuracy of stroke volume variation and pulse pressure variation to predict fluid responsiveness in patients with thoracic kyphosis

Abstract

Background: This study aims to evaluate the ability of stroke volume variation (SVV) and pulse pressure variation (PPV) to predict fluid responsiveness in mechanically ventilated patients with thoracic kyphosis.

Methods: A total of 35 patients diagnosed with thoracic kyphosis undergoing corrective surgery were studied. For all patients, the Vigileo/FloTrac system was used for analysis. Hemodynamic data such as mean arterial pressure (MAP), heart rate (HR), stroke volume (SV), stroke volume index (SVI), cardiac output (CO), cardiac output index (CI), SVV, and PPV were recorded before and after volume expansion (VE). Fluid responsiveness was defined as an increase in SVI ≥10% (ΔSVI ≥10%). Patients were divided into responders and non-responders as determined by changes in ΔSVI ≥10% and <10%. Nonparametric Wilcoxon rank sum test was used to compare the hemodynamic parameters of Responders and Non-responders before and after VE. Pearson correlation analysis was used to analyze the values of SVV, PPV and ΔSVI. The receiver operating characteristic (ROC) curve of each hemodynamic index was drawn to determine its accuracy and threshold.

Results: Two patients were excluded. There was no significant difference in patients' characteristics between Responders and Non-responders. After VE, there were no significant changes in HR, MAP, and SV in both responders and non-responders, but CI were significantly changed in the two groups. SVI and CO increased significantly in responders before and after VE, but not in non-responders. VE also caused decreases of PPV and SVV in both responders and non-responders. Before VE, the SVV and PPV correlated with ΔSVI in responders (r=0.621, r=0.569, respectively, P<0.05), but neither the SVV nor PPV correlated with ΔSVI in non-responders (P>0.05). The areas under the ROC curves of patients with thoracic kyphosis were 0.872 (95% CI: 0.719-1.000) for SVV and 0.833 (95% CI: 0.667-1.000) for PPV. The threshold of the SVV of patients with thoracic kyphosis was 13.5%, and the threshold of PPV was 14.5%.

Conclusions: Both SVV and PPV can be used as effective indictors to monitor volume changes in patients with thoracic kyphosis.

Keywords: Stroke volume variation (SVV); pulse pressure variation (PPV); thoracic kyphosis.