CICM SAQ 2014.1 Q8

a) List the determinants of central venous pressure (CVP).

b) Discuss the role of CVP monitoring in the critically ill.

Answer
Answer and interpretation

a) List the determinants of central venous pressure (CVP).

Determinants of CVP:

  • Intravascular volume status
  • Mean systemic filling pressure
  • Right and left ventricular status and compliance
  • Pulmonary vascular resistance
  • Venous capacitance / tone
  • Intra-thoracic pressure
  • Intra-abdominal pressure

b) Discuss the role of CVP monitoring in the critically ill.

  • For example: CVP is the pressure recorded from the right atrium or superior vena cava and is representative of the filling pressure of the right side of the heart. CVP monitoring in the critically ill is established practice but the traditional belief that CVP reflects ventricular preload and predicts fluid responsiveness has been challenged.

Most critically ill patients have central venous vascular access with multi-lumen catheters, making CVP monitoring easy to do.

Information derived from the waveform and/or measured value assists with / assists the diagnosis of:

  • Confirmation of correct line placement.
  • Tricuspid regurgitation or stenosis.
  • Complete heart block.
  • Constrictive pericarditis.
  • Tamponade.
  • Right ventricular infarction.
  • Differential diagnosis of shock state.
  • Determining mechanical atrial capture with AV pacing.
  • Determining the presence of P waves in cases of SVT.

Traditionally, CVP measurement has been used to assess fluid responsiveness – including assessment of change in CVP after fluid boluses – and the use of target values as resuscitation end-points as recommended in the Surviving Sepsis Guidelines. However increasing evidence including a recent meta-analysis (Marik in Chest) has shown there is no correlation between CVP and fluid status and targeting a certain CVP value can lead to overload in one patient and to another remaining hypovolaemic. Current thinking suggests that interpretation of CVP should be in association with information relating to other haemodynamic variables.
Complications associated with CVC insertion means that CV monitoring is not risk-free. Correct placement, calibration and measurement (at end-expiration) are needed to obtain an accurate recording. Simultaneous fluid administration through the CVC leads to inaccuracies.

Alternative monitoring modalities include devices such as PiCCO and Vigileo analysing stroke volume variation, pulse contour analysis, global end-diastolic blood volume, etc. and bedside echo.

Summary

  • For example: CVP monitoring may contribute information relating to the haemodynamic state of a patient but the value must be interpreted in the context of what else is known about that patient’s cardiac function. Use of CVP as a measure of fluid responsiveness is flawed. The increasing use of bedside echo in the ICU is decreasing the utility of CVP monitoring.
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Chris is an Intensivist and ECMO specialist at the Alfred ICU in Melbourne. He is also the Innovation Lead for the Australian Centre for Health Innovation at Alfred Health and Clinical Adjunct Associate Professor at Monash University. He is a co-founder of the Australia and New Zealand Clinician Educator Network (ANZCEN) and is the Lead for the ANZCEN Clinician Educator Incubator programme. He is on the Board of Directors for the Intensive Care Foundation and is a First Part Examiner for the College of Intensive Care Medicine. He is an internationally recognised Clinician Educator with a passion for helping clinicians learn and for improving the clinical performance of individuals and collectives.

After finishing his medical degree at the University of Auckland, he continued post-graduate training in New Zealand as well as Australia’s Northern Territory, Perth and Melbourne. He has completed fellowship training in both intensive care medicine and emergency medicine, as well as post-graduate training in biochemistry, clinical toxicology, clinical epidemiology, and health professional education.

He is actively involved in in using translational simulation to improve patient care and the design of processes and systems at Alfred Health. He coordinates the Alfred ICU’s education and simulation programmes and runs the unit’s education website, INTENSIVE.  He created the ‘Critically Ill Airway’ course and teaches on numerous courses around the world. He is one of the founders of the FOAM movement (Free Open-Access Medical education) and is co-creator of litfl.com, the RAGE podcast, the Resuscitology course, and the SMACC conference.

His one great achievement is being the father of two amazing children.

On Twitter, he is @precordialthump.

| INTENSIVE | RAGE | Resuscitology | SMACC

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