Dynamic Indices Fail to Predict Fluid Responsiveness in Patients Undergoing One-Lung Ventilation for Thoracoscopic...

Thoracic surgery using CO₂ insufflation maintains closed-chest one-lung ventilation (OLV) that may provide the necessary heart-lung interaction for the dynamic indices to predict fluid responsiveness. We studied whether pulse pressure variation (PPV) and stroke volume variation (SVV) can predict fluid responsiveness during thoracoscopic surgery. Forty patients were enrolled in the study. OLV was performed with a tidal volume of 6 mL/kg at a positive end-expiratory pressure of 5 cm H₂O, while CO₂ was insufflated to the contralateral side at 8 mm Hg. Patients whose stroke volume index (SVI) increased ≥15% after fluid challenge (7 mL/kg) were defined as fluid responders. The predictive ability of PPV and SVV on fluid responsiveness was investigated using the area under the receiver-operator characteristic curve (AUROC), which was also assessed according to the right or left lateral decubitus position considering the intrathoracic location of the right-sided superior vena cava. AUROCs of PPV and SVV for predicting fluid responsiveness were 0.65 (95% confidence interval 0.47-0.83, p = 0.113) and 0.64 (95% confidence interval 0.45-0.82, p = 0.147), respectively. The AUROCs of indices did not exhibit any statistical significance according to position. Dynamic indices of preload cannot predict fluid responsiveness during one-lung ventilation with CO₂ gas insufflation.