Central venous pressure

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.

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:

Hypovolemia

Deep inhalation

Distributive shock

Low Central Venous Pressure

Some factors that can decrease central venous pressure are hypovolemia or venodilation. Either of these would decrease venous return and thus decrease the central venous pressure. A decrease in central venous pressure is noted when there is more than 10% of blood loss or shift of blood volume. A decrease in intrathoracic pressure caused by forced inspiration causes the vena cavae to collapse which decreases the venous return and, in turn, decreases the central venous pressure.

Elevated Central Venous Pressure

Elevated Central Venous Pressure can occur in heart failure due to decreased contractility, valve abnormalities, and dysrhythmias. Any patients on ventilator assistance that have excessive positive end-expiratory pressure would have an increase in pulmonary arterial resistance which causes an increase in central venous pressure. However, an increased central venous pressure caused by increased pulmonary arterial resistance can also be affected by a decrease in the fraction of inspired oxygen, an increase in ventilation/perfusion abnormalities in the lung, an increase in pericardial pressure, or an increase in intra-abdominal pressure which would increase thoracic pressure. Increased juxta-cardiac pressure - tension pneumothorax, pericardial tamponade, right ventricular infarct, right ventricular outflow obstruction - can also decrease venous return.

Clinical Significance

The clinical utility of the central venous pressure can be seen in the assessment of cardiocirculatory status. Elevated CVP will present clinically as a pulsation of the internal jugular vein when a patient is inclined at 45 degrees; however, it can be noted in an upright patient in severe cases.

Elevated CVP is indicative of myocardial contractile dysfunction and/or fluid retention. On the other hand, low central venous pressure is indicative of volume depletion or decreased venous tone. The central venous pressure, despite its numerous limitations, is consistently used universally to guide fluid resuscitation.

The ease of determination of the central venous pressure makes it a clinically attractive, albeit non-specific, indicator of fluid status. As such, other indices, such as the inferior vena cava collapsibility index (IVC CI), must be used adjunctively for a more accurate assessment of volume status.

In addition, CVP has been found to be inversely correlated with the tricuspid annular plane systolic excursion (TAPSE) in mechanically ventilated critically ill patients (with left ventricular ejection fraction (LVEF) less than 55%) thus, TAPSE may be used as a surrogate marker of CVP.

References:

https://www.ncbi.nlm.nih.gov/books/NBK519493/

Govender J, Postma I, Wood D, Sibanda W. Is there an association between central venous pressure measurement and ultrasound assessment of the inferior vena cava? Afr J Emerg Med. 2018 Sep;8(3):106-109. [PMC free article] [PubMed]

Zhang H, Wang X, Chen X, Zhang Q, Liu D. Tricuspid annular plane systolic excursion and central venous pressure in mechanically ventilated critically ill patients. Cardiovasc Ultrasound. 2018 Aug 07;16(1):11. [PMC free article] [PubMed]

http://en.wikipedia.org/wiki/Central_venous_pressure