Central Venous Pressure

Definitions

Central Venous Pressure (CVP)
1. Grouping of venous pressures that are equivalent to one another
  1. Superior Vena Cava Pressure
  2. Right Atrial Pressure (RAP)
2. CVP is also equivalent to the right ventricular end diastolic pressure (RVEDP) and Preload
  1. Only if no tricuspid insufficiency
Right Ventricular End-Diastolic Pressure (RVEDP)
1. Equivalent to CVP (in the absence of tricuspid insufficiency)

Images

Cardiac Cycle Volumes and Pressures (Wiggers Diagram)

Technique
Central Venous Pressure (CVP)

Catheters
1. Central venous catheter or
2. Pulmonary artery catheter (Swans-Ganz Catheter) via proximal port in atrium
  1. Contrast with distal port in pulmonary vessels (pulmonary wedge pressure) reflecting left atrial pressure
3. PICC Lines are not used for CVP measurement due to long length
  1. Theoretically could be used with saline infusion
  2. Black (2000) Crit Care Med 28:3833-36 [PubMed]
Transducer
1. Fluid-filled device measures pressure readings from catheter
2. Placed at the same level as the right atrium
  1. Landmarks for the supine patient
    1. Intersection of the fourth intercostal space and the mid-axillary line
  2. Landmarks for the semi-recumbent patient (<60 degrees)
    1. Below the sternal angle by 5 cm (directly down)
Measurement
1. Record at the end of expiration (when intrathoracic pressure is closest to atmospheric pressure)
2. CVP varies with respiration (spontaneous and Mechanical Ventilation)
  1. CVP decreases with spontaneous inspiration (decreased intrathoracic pressure)
  2. CVP increases with Mechanical Ventilation (positive pressure increases intrathoracic pressure)

Interpretation

Normal Central Venous Pressure (CVP or RAP, Right Atrial Pressure)
1. Normal CVP 2 to 8 mmHg (some references list 0 to 5 mmHg)
2. Measurements vary as much as 4 mm Hg in the same patient under the same conditions
  1. CVP change is only significant if changes more than 4 mmHg
Other Normal Right Sided Pressures
1. Right Ventricular Pressure = 25/2 mmHg
2. Pulmonary Artery Pressure (PAP) = 25/12 mmHg
3. Mean Pulmonary Artery Pressures = 16 mmHg
4. Mean Pulmonary Capillary Wedge Pressure (or left atrial pressure): 9 mmHg
CVP may be increased initially despite significant volume depletion
1. Consider underlying COPD, Vasoconstriction
2. Consider increased intrathoracic pressure (Tension Pneumothorax, Positive Pressure Ventilation)
3. Consider Diastolic Dysfunction with decreased right ventricular compliance (MI, Sepsis, valvular dysfunction)
4. Peristently increased CVP suggests adequate volume replacement or Fluid Overload
CVP that is markedly increased
1. Fluid Overload (Edematous States such as Congestive Heart Failure, liver failure, Renal Failure)
2. Cardiac Tamponade
3. Tension Pneumothorax
4. Central catheter malposition
CVP that is low with signs of shock and minimally rises with fluid bolus
1. Continue Fluid Replacement (or Blood Products in the case of Hemorrhagic Shock)
2. Consider source of ongoing losses
CVP that is decreasing with signs of shock
1. Aggressively search for ongoing losses (e.g. Hemorrhagic Shock)
2. Continue Fluid Replacement (or Blood Products in the case of Hemorrhagic Shock)
3. Vasopressors as needed

Precautions

CVP is an indirect, invasive and often inaccurate surrogate for Ventricular Preload and volume status
1. Consider Inferior Vena Cava Ultrasound for Volume Status as an alternative
End diastolic pressure (e.g. CVP and Wedge Pressure) correlates poorly with end diastolic volume even in healthy patients
1. Hence CVP and Wedge Pressure are unreliable markers of ventricular filling and volume status
CVP is falsely elevated with increased intrathoracic pressure (e.g. PPV, PEEP)

References

Marino (2014) ICU Book, 4th Ed Wolters-Kluwer p. 157-9
(2012) ATLS Manual, 9th ed, American College of Surgeons
Killu and Sarani (2016) Fundamental Critical Care Support, p. 93-114