Medicine:Central venous pressure
Central venous pressure (CVP) is the blood pressure in the venae cavae, 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 back into the arterial system. CVP is often a good approximation of right atrial pressure (RAP),[1] although the two terms are not identical, as a pressure differential can sometimes exist between the venae cavae and 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 systemic vascular resistance while increasing heart rate and ventricular contractility in dogs.[4]
Measurement
Normal CVP in patients can be measured from two points of reference:[citation needed]
- 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.[citation needed]
In most intensive care units, facilities are available to measure CVP continuously.[citation needed]
Normal values vary between 4 and 12 cm H2O.
Factors affecting CVP
Factors that increase CVP include:[citation needed]
- Cardiac tamponade
- Decreased cardiac output
- Forced exhalation
- Heart failure
- Hypervolemia
- Mechanical ventilation and the application of positive end-expiratory pressure (PEEP)
- Pleural effusion
- Pulmonary embolism
- Pulmonary hypertension
- Tension pneumothorax
Factors that decrease CVP include:
- Deep inhalation
- Distributive shock
- Hypovolemia
See also
- Jugular venous pressure
- Pulmonary capillary wedge pressure
References
- ↑ "Central Venous Catheter Physiology". http://www.healthsystem.virginia.edu/internet/anesthesiology-elective/cardiac/cvcphys.cfm.
- ↑ "Pulmonary artery occlusion pressure and central venous pressure fail to predict ventricular filling volume, cardiac performance, or the response to volume infusion in normal subjects". Crit Care Med 32 (3): 691–699. 2004. doi:10.1097/01.ccm.0000114996.68110.c9. PMID 15090949. http://www.gwicu.com/Assets/Articles/PCPW%20CVP%20Ventric%20filling%20Kumar%20CCM%202004.pdf.
- ↑ "Does Central Venous Pressure Predict Fluid Responsiveness?". Chest 134 (1): 1351–1352. July 2008. doi:10.1378/chest.08-1846. PMID 19059974. http://journal.publications.chestnet.org/data/Journals/CHEST/22074/zcb00708000172.pdf. Retrieved 2012-12-09.
- ↑ "Stimulation of the Cardiopulmonary Baroreflex Enhances Ventricular Contractility in Awake Dogs: A Mathematical Analysis Study". American Journal of Physiology. Regulatory, Integrative and Comparative Physiology 307 (4): R455–R464. June 2014. doi:10.1152/ajpregu.00510.2013. PMID 24944253.
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 and Pulmonary Capillary Wedge Monitoring
- Cardiovascular Physiology
- Central+Venous+Pressure at the US National Library of Medicine Medical Subject Headings (MeSH)
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