Objectives: To determine the possibility of non-invasive estimation of central venous pressure (CVP) through inferior vena cava (IVC) analysis, using transthoracic echocardiography (TTE).
Design: A prospective 3-year study.
Setting: A 16-bed medical/surgical Intensive Care Unit (ICU).
Methods: Patients admitted to the ICU were enrolled. CVP measurement and TTE (determining cardiac chambers dimension and left ventricular shortening fraction) with IVC analysis (maximum dimension and IVC index) were performed simultaneously. Parametric and non-parametric statistical analysis was performed to establish correlations between variables.
Results: 560 patients were admitted to the study, including 477 in whom IVC was analysed, aging 62.2 +/- 17.3 years, a mean ICU stay 11.9 +/- 18.7 days, a APA- CHE II score 23.9 +/- 8.9 and a SAPS II score 55.7 +/- 20.4. Through linear regression analysis CVP was influenced by IVC index (p=0.001), IVC maximum dimension (p=0.013) and presence of mechanical ventilation (p=0.002). A statistically significant correlation was found between the following parameters: an IVC index < 25% and a CVP > 13 mmHg; an IVC index and a CVP 26%-50%; an IVC index > 51% and CVP < 7 mmHg; an IVC maximum dimension > 20mm and a CVP > 13 mmHg; an IVC maximum dimension < 10 mmHg and CVP < 7 mmHg. Patients with right ventricle enlargement presented a lack of agreement between IVC maximum dimension and CVP > 7 mmHg was observed, and in patients with chronic respiratory failure (who presented a high prevalence of right ventricular enlargement) a lack of agreement between IVC index > 50% and CVP < 7 mmHg was also observed.
Conclusions: IVC analysis is a possible way to non-invasively estimate CVP in a medical /surgical ICU. However, patients with right ventricular enlargement and admitted with chronic respiratory failure present a lack of agreement between IVC parameters and low values of CVP. IVC dimension is a marker of chronic disease and IVC index correlated better with CVP.