Estimation of Central Venous Pressure using Ultrasound Imaging of Inferior Vena Cava

PURPOSE: There have been several studies addressing the correlation between central venous pressure (CVP) and ultrasonographic findings of the inferior vena cava (IVC). We performed the present study to discover the degree of correlation between CVP and the area of IVC as measured with ultrasound, and to determine which portion of the IVC shows the best correlation with CVP. METHODS: The present study was prospectively performed in emergency medical center of Chonnam National University Hospital from March 1 to October 31, 2006. Two intrahepatic portions and one extrahepatic portion of the IVC were evaluated. RESULTS: All tested areas of the IVC, and the collapsibility indices measured at each location, showed a substantial correlation with CVP. However, in multiple logistic regression analysis performed to identify the location best correlated with CVP, the area of the IVC just below the hepatic vein-IVC junction proved to be the only location to correlate with CVP with statistic significance. CONCLUSION: Measurement of IVC area using ultrasound can yield important information about a patient's volume status, especially in patients for whom central venous catheter insertion is contraindicated. We suggest that the portion of the IVC just below the hepatic vein-IVC junction is the optimal locatin for area measurement to estimate CVP.

Comparison of the Potassium Concentrations Measured by Using Blood Gas Analyzers and Automated Chemical Analyzers

PURPOSE: Critically ill patients frequently require rapid measurements of serum potassium. Analyses of serum samples take some time, but the results of blood gas analyses are often available more promptly. This study aims to determine the correlation between potassium concentrations measured by blood gas analyzer and automated chemical analyzer with a view to identifying whether the plasma potassium level can be used as an alternative to the serum values in the clinical management of selected patients in the Emergency Department (ED). METHODS: This prospective study of patients who were deemed by their treating doctor to require a blood gas analysis and chemistry analysis compared the potassium concentrations obtained from plasma and serum taken simultaneously. Data were analyzed using a Pearson correlation and a linear regression. RESULTS: Four hundred ninety-six patients were entered into the study. The potassium concentrations measured using two blood gas analyzers and two automated chemical analyzers were relatively highly correlated (coefficient=0.871), with an average difference between two methods of 0.449 mmol/L. There was also a high level of agreement between the methods with the 95% limits of agreement being -0.2 to 1.2 mmol/L. CONCLUSION: Compared with data from other previous test, our data were unsatisfactory. However our trial makes it possible in our ED to obtain serum potassium level from the plasma level. In addition, hypokalemia obtained by blood gas analyzer should be made an exception in treating it.