Comparison of bedside methods to estimate CVP

Rationale:
It is unknown how different bedside, non-invasive methods to estimate central venous pressure (CVP) (visual assessment of the height of the fluid column in the right external jugular vein (EJV) according to Lewis and Borst, ultrasonography of the right internal jugular vein (IJV) and ultrasonography of the inferior vena cava (IVC)) correlate with each other and which method has the best accuracy in estimating CVP in critically ill patients.
Objective:
To compare the accuracy of the above-mentioned methods in patients admitted to the ward and intensive care unit in estimating CVP and to investigate the correlation between the different methods.
Study design:
A prospective observational, one center clinical study.
Study population:
Patients of 18 years or older admitted to the ward or intensive care unit who (already) have an indwelling central venous catheter for clinical indications and who are not undergoing positive pressure ventilation.
Main study parameters/endpoints:
Primary endpoints:
- Differences in test characteristics (sensitivity and specificity after determination of optimal cut-off with receiver operating characteristic curves as compared to the gold standard of the CVP measured in the superior vena cava by means of a central venous catheter) of the bedside tests to assess elevated CVP (according to Lewis and Borst, with and without correction for the vertical distance between the right atrium and the sternal angle; ultrasonographic measurement of maximum width and collapsibility of the IVC; and ultrasonographic measurement of the diameter and height of the IJV).
Secondary endpoints:
- The correlation between estimates of CVP as measured according to Lewis and Borst (with and without correction for the vertical distance between the right atrium and the sternal angle), ultrasonography of the IVC and ultrasonography of the IJV.
- The correlation of the above-mentioned measures with the gold standard; the CVP measured in the superior vena cava by means of a central venous catheter.
Nature and extent of the burden and risks associated with participation, benefit and group relatedness:
Measurements of the CVP as measured according to Lewis and Borst and ultrasonography of the VCI and IJV are both non-invasive assessments. Like the measurement of the CVP by central venous catheter, all measurements are part of the routine care in patients admitted on the intensive care unit. In patients admitted to the ward only already inserted catheters will be used, no invasive interventions will be performed. There is no risk, burden or physiological discomfort to be expected.

The results of this study may answer the question whether these methods are complementary or if one of these methods may be abandoned in favour of the others. Adopting one method in clinical practice may save time in the assessment of acutely ill patients. Moreover, the results of this study may lead to a better interpretation of tests that are already in current use, but whose value we do not fully understand at present.

At the day of admittance with or the day of insertion of a central venous catheter the CVP will be estimated by the different methods:

- Height of the fluid column of the right external jugular vein above the reference point, the sternal angle and above the right atrium according to Lewis and Borst in cm
- Height of the fluid column above the right atrium; maximal diameter and minimal diameter during spontaneous inspiration in cm measured by ultrasound
- Inferior vena cava, 2 cm from the right atrium; maximal diameter, minimal diameter during spontaneous inspiration and minimal diameter during sniffing in cm measured by ultrasound
- Inferior vena cava, immediately before the right atrium; maximal diameter, minimal diameter during spontaneous inspiration and minimal diameter during sniffing in cm measured by ultrasound
- Inferior vena cava, at the hepatic vein junction; maximal diameter, minimal diameter during spontaneous inspiration and minimal diameter during sniffing in cm measured by ultrasound
- CVP at the end of an expiration in mmHg by central intravenous catheter
- Stroke volume variation in % by central intravenous catheter if available

All measurements will be done by two physicians at the same day, shortly after the other.

None