Inferior Vena Cava Diameter (IVCD) Measured with Transesophageal Echocardiography (TEE) Can Be Used to Derive the Central Venous Pressure (CVP) in Anesthetized Mechanically Ventilated Patients

BACKGROUND: Estimation of right atrial pressure (RAP) from variations in the diameter of the inferior vena cava (IVC) during the respiratory cycle using transthoracic echocardiography (TTE) is used routinely to calculate pulmonary artery systolic pressure, adding to right ventricular systolic pressure (RVSP) from the jet velocity of tricuspid regurgitation. Using transesophageal echocardiography (TEE) we sought to determine if the inferior vena cava diameter (IVCD) could be used to derive the central venous pressure (CVP) in anesthetized, mechanically ventilated patients. METHODS: The IVCD was measured in its long axis (bicaval view) at the cavo-atrial junction using TEE and ECG synchronization (to coincide with the end of the T-wave) in 95 anesthetized, mechanically ventilated patients undergoing elective cardiac surgery. Each patient received a pulmonary artery catheter (PAC) that allowed for continuous monitoring of the CVP. Three independent readers were assigned to document the IVCD and the CVP. Statistical analysis was performed using bivariate correlation, variance (ANOVA), linear regression, Bland-Altman and Passing-Bablock analysis of agreement. RESULTS: The IVCD measured in millimeters at the cavo-atrial junction showed a positive correlation with the CVP (n = 95, r = 0.860, P < 0.0001, r(2)= 0.737, P < 0.0001). The linear regression equation [CVPc = (IVCD-4.004/0.751] was prospectively tested in a cohort of 12 anesthetized, mechanically ventilated patients under various hemodynamic conditions with a good correlation between the mean CVP (CVPm) and the calculated CVP (CVPc) (r = 0.923, P < 0.0001, r(2)= 0.851, P < 0.0001). CONCLUSION: The TEE measured IVCD at the cavo-atrial junction showed a statistically significant correlation with the mean CVP. Using an equation derived from linear regression analysis, a reliable CVP can be estimated from the IVCD.