Central venous pressure
Encyclopedia
Central venous pressure (also known as: right atrial pressure; RAP) describes 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.
It is a good approximation of right atrial pressure, which is a major determinant of right ventricular end diastolic volume. 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. Nevertheless, CVP monitoring is a useful tool to guide hemodynamic therapy.
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 progressive intensive care unit
s in the U.S., specialized monitors are available to continuously measure CVP as well as other hemodynamic values.
Normal values are 2–8 mmHg
Factors that decrease CVP include:
Right atrium
The right atrium is one of four chambers in the hearts of mammals and archosaurs...
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.
It is a good approximation of right atrial pressure, which is a major determinant of right ventricular end diastolic volume. 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
Cardiac output
Cardiac output is the volume of blood being pumped by the heart, in particular by a left or right ventricle in the time interval of one minute. CO may be measured in many ways, for example dm3/min...
). 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. Nevertheless, CVP monitoring is a useful tool to guide hemodynamic therapy.
Measurement
Normal CVP can be measured from two points of reference:- Sternum: 0–14 cm H2OCentimetre of waterA centimetre of water is a less commonly used unit of pressure derived from pressure head calculations using metrology...
- Midaxillary lineMidaxillary lineThe midaxillary line is a coronal line on the torso between the anterior axillary line and the posterior axillary line.It is a landmark used in thoracentesis.-External links:* http://www.meddean.luc.edu/Lumen/MedEd/MEDICINE/PULMONAR/apd/lines.htm...
: 8–15 cm H2O
CVP can be measured by connecting the patient's central venous catheter
Central venous catheter
In medicine, a central venous catheter is a catheter placed into a large vein in the neck , chest or groin...
to a special infusion
Infusion pump
An infusion pump infuses fluids, medication or nutrients into a patient's circulatory system. It is generally used intravenously, although subcutaneous, arterial and epidural infusions are occasionally used....
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 progressive intensive care unit
Intensive Care Unit
thumb|220px|ICU roomAn intensive-care unit , critical-care unit , intensive-therapy unit/intensive-treatment unit is a specialized department in a hospital that provides intensive-care medicine...
s in the U.S., specialized monitors are available to continuously measure CVP as well as other hemodynamic values.
Normal values are 2–8 mmHg
Factors affecting CVP
Factors that increase CVP include:- HypervolemiaHypervolemiaHypervolemia, or fluid overload, is the medical condition where there is too much fluid in the blood.The opposite condition is hypovolemia, which is too little fluid volume in the blood.-Causes:Excessive sodium or fluid intake:* IV therapy...
- forced exhalationExhalationExhalation is the movement of air out of the bronchial tubes, through the airways, to the external environment during breathing....
- Tension pneumothorax
- Heart failure
- Pleural effusionPleural effusionPleural effusion is excess fluid that accumulates between the two pleural layers, the fluid-filled space that surrounds the lungs. Excessive amounts of such fluid can impair breathing by limiting the expansion of the lungs during ventilation.-Pathophysiology:...
- Decreased cardiac outputCardiac outputCardiac output is the volume of blood being pumped by the heart, in particular by a left or right ventricle in the time interval of one minute. CO may be measured in many ways, for example dm3/min...
- Cardiac tamponadeCardiac tamponadeCardiac tamponade, also known as pericardial tamponade, is an emergency condition in which fluid accumulates in the pericardium ....
- Mechanical ventilationMechanical ventilationIn medicine, mechanical ventilation is a method to mechanically assist or replace spontaneous breathing. This may involve a machine called a ventilator or the breathing may be assisted by a physician, respiratory therapist or other suitable person compressing a bag or set of bellows...
and the application of positive end-expiratory pressure (PEEP)
Factors that decrease CVP include:
- HypovolemiaHypovolemiaIn physiology and medicine, hypovolemia is a state of decreased blood volume; more specifically, decrease in volume of blood plasma...
- Deep inhalation
- Distributive shockDistributive shockDistributive shock is defined by hypotension and generalized tissular hypoxia. This form of relative hypovolemia is the result of blood vessel dilation...
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
See also
Pulmonary Capillary Wedge PressurePulmonary capillary wedge pressure
The pulmonary capillary wedge pressure or PCWP is the pressure measured by wedging a pulmonary catheter with an inflated balloon into a small pulmonary arterial branch.Physiologically, distinctions can be drawn among pulmonary venous pressure, pulmonary artery pressure, pulmonary...