Ultrasound imaging and central venous pressure in spontaneously breathing patients: a comparison of ultrasound-based measures of internal jugular vein and inferior vena cava

BACKGROUND: Ultrasound evaluation of inferior vena cava and internal jugular vein dia-meters predicts the intravascular volume status in critical patients. The aim of the present study was to determine which ultrasound-derived index is most strongly associated with central venous pressure (CVP). Furthermore, we determined the utility of selected variables in predicting low volume status (CVP < 8 mmHg). METHODS: All patients underwent a transthoracic echocardiogram, vascular ultrasound examination, invasive central venous pressure, and intra-abdominal pressure determination. The following indexes were calculated: inferior vena cava diameter, internal jugular vein maximum diameter, collapsibility index, and internal jugular vein ratio. RESULTS: 41 spontaneously breathing patients were recruited. Central venous pressure significantly correlated with inferior vena cava diameter (r = 0.35, P = 0.02), internal jugular vein ratio (r = 0.35, P = 0.03), and internal jugular vein maximum diameter (r = 0.58, P < 0.001). The inferior vena cava collapsibility index did not show any association. The areas under the receiver operating characteristic curves to discriminate a low central venous pressure (< 8 mmHg) were the following: internal jugular vein diameter 0.80 (95% CI: 0.63–0.90); inferior vena cava diameter 0.66 (95% CI: 0.49–0.80); and internal jugular vein ratio 0.68 (95% CI: 0.51–0.82). CONCLUSIONS: The internal jugular vein diameter, the internal jugular vein ratio, and the inferior vena cava diameter showed a significant correlation with central venous pressure. In particular, the internal jugular vein diameter showed good accuracy in predicting a low central venous pressure.