Question 14

Created on Wed, 06/03/2015 - 16:32
Last updated on Sun, 08/09/2015 - 10:08
Pass rate: ?
Highest mark: ?

Other SAQs in this paper

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What are  the determinants of central  venous pressure?    How may its measurement guide patient management?

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College Answer

Central venous pressure (CVP) is dependent on intravascular fluid volume, right ventricular function, pulmonary vascular resistance, venous capacitance, intrathoracic pressure, ventricular compliance and viz a tergo (arterial pressure).

Measurement of CVP is used as an indirect guide of right ventricular filling but any absolute measure has a complex relationship with right ventricular preload. If other conditions are constant, trends in CVP may reflect vascular compliance and changes in volume status.

Absolute measures along with pulmonary wedge pressure may help in the diagnosis of:

-    right ventricular infarction

-     pulmonary embolus

-     ARDS severity

-     Cor pulmonale

-     tamponade

CVP waveforms may indicate nodal rhythm, tricuspid incompetence etc

Discussion

This question closely resembles Question 8 from the first paper of 2014.

However, the college answer for the 2014 version is a massive improvement on this 2001 version.

Factors which determine CVP:

  • Reference level of the transducer
  • Intravasculr volume
    • and the distribution of this volume between the venous and arterial compartment
  • Central venous compliance
  • Right ventricular compliance
    • myocardial or pericardial disease; tamponade
  • Right ventricular systolic function
  • Cardiac rhythm (i.e. AF vs. sinus rhythm)
  • Tricuspid valve disease
  • Pulmonary vascular resistance
  • Intrathoracic pressure

Influence of central venous pressure on patient management

The relationship of CVP to preload and fluid responsiveness is discussed in greater detail elsewhere.

In general, one can divide this answer into two components:

Pressure analysis

  • Assists the diagnosis of cardiac failure
  • Assists decisionmaking regarding fluid resuscitation (though this is not supported by evidence)
  • Informs hemodynamic management in situations where CVP is surgically important (eg. in hepatic resection or transplant)

Waveform analysis

  • Informative regarding tricuspid disease
  • Informative regarding atrial contractility

References

Most of this material can be found in Bersten and Soni’s” Oh's Intensive Care Manual”, 6th Edition, as well as the CVC section from The ICU Book by Paul L Merino (3rd edition, 2007)

Marik, Paul E., and Rodrigo Cavallazzi. "Does the central venous pressure predict fluid responsiveness? An updated meta-analysis and a plea for some common sense*." Critical care medicine 41.7 (2013): 1774-1781.