Diagnostic Accuracy of Dynamic Central Venous Oxygen Saturation in Predicting Fluid Responsiveness in Septic Shock: A Prospective Observational Study

All patients will undergo standardized monitoring to ensure accurate and reproducible hemodynamic assessment throughout the study period.

Blood pressure will be monitored noninvasively using an automated oscillometric cuff applied to the upper arm. MAP will be maintained at ≥65 mmHg with vasopressor support as required, and no changes in vasopressor infusion will be permitted during the measurement period.

A central venous catheter will be inserted in the internal jugular or subclavian vein, with the position confirmed by chest radiography. Central venous blood samples will be collected at baseline and after the fluid challenge for the determination of a Central venous oxygen saturation (ScvO₂).

Echocardiographic Assessment Left ventricular outflow tract (LVOT) diameter will be measured in the parasternal long-axis view by transthoracic echocardiography (Sonoscape S8 Echocardiography), and Doppler assessment of velocity- time integral (VTI) will be obtained in the apical five-chamber view. Stroke volume (SV) will be calculated as LVOT area × VTI, and values will be averaged from three consecutive cardiac cycles over a single respiratory cycle. The echocardiography operator will be an expert intensivist in echo operation (more than 7 years of experience), and the operator will be blinded to ScvO2.

Cardiac Output Monitoring (Electrical Cardiometry) Cardiac output will also be assessed noninvasively using a validated electrical cardiometry device (ICON®, Osypka Medical, Germany).