Central venous pressure
Central venous pressure (CVP), also known as mean venous pressure (MVP) is the pressure of blood in the thoracic vena cava, near the right atrium of the heart. CVP reflects the amount of blood returning to the heart and the ability of the heart to pump the blood into the arterial system. CVP is often a good approximation of right atrial pressure (RAP),[1] however the two terms are not identical, as right atrial pressure is the pressure in the right atrium. CVP and RAP can differ when arterial tone is altered. This can be graphically depicted as changes in the slope of the venous return plotted against right atrial pressure (where central venous pressure increases, but right atrial pressure stays the same; VR = CVP-RAP).
CVP has been, and often still is, used as a surrogate for preload, and changes in CVP in response to infusions of intravenous fluid have been used to predict volume-responsiveness (i.e. whether more fluid will improve cardiac output). However, there is increasing evidence that CVP, whether as an absolute value or in terms of changes in response to fluid, does not correlate with ventricular volume (i.e. preload) or volume-responsiveness, and so should not be used to guide intravenous fluid therapy.[2][3] Nevertheless, CVP monitoring is a useful tool to guide hemodynamic therapy. The cardiopulmonary baroreflex responds to an increase in CVP by decreasing total peripheral resistance while increasing HR and ventricular contractility in dogs.[4]
Measurement
| Site | Normal pressure range (in mmHg)[5] |
|
|---|---|---|
| Central venous pressure | 3–8 | |
| Right ventricular pressure | systolic | 15–30 |
| diastolic | 3–8 | |
| Pulmonary artery pressure | systolic | 15–30 |
| diastolic | 4–12 | |
| Pulmonary vein/ |
2–15 | |
| Left ventricular pressure | systolic | 100–140 |
| diastolic | 3-12 | |
Normal CVP can be measured from two points of reference:
- Sternum: 0–14 cm H2O
- Midaxillary line: 8–15 cm H2O
CVP can be measured by connecting the patient's central venous catheter to a special infusion set which is connected to a small diameter water column. If the water column is calibrated properly the height of the column indicates the CVP.
In most intensive care units, facilities are available to measure CVP continuously.
Normal values vary between 4 and 12 cmH2O。[6]
Factors affecting CVP
Factors that increase CVP include:
- Hypervolemia
- forced exhalation
- Tension pneumothorax
- Heart failure
- Pleural effusion
- Decreased cardiac output
- Cardiac tamponade
- Mechanical ventilation and the application of positive end-expiratory pressure (PEEP)
- Pulmonary Hypertension
- Pulmonary Embolism
Factors that decrease CVP include:
See also
References
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External links
- Venous function and central venous pressure: a physiologic story - a technical discussion of the more modern understanding of central venous pressure; this may well conflict with the sources below.
- Central Venous Pressure Monitoring
- Cardiovascular Physiology Concepts
- Central Venous Pressure and Pulmonary Capillary Wedge Monitoring
- Cardiovascular Physiology
- Central Venous Pressure at the US National Library of Medicine Medical Subject Headings (MeSH)
