Haemodynamic monitoring

CVP and ScvO2

Reviewed Nov 2026·5 references
New· views rounded down, updated weekly

What CVP and central venous oxygen saturation can and cannot tell you, and how to use them sensibly.

Definition
CVP = pressure in the superior vena cava/right atrium (normal 2-8 mmHg spontaneously breathing). ScvO2 = oxygen saturation of blood from a CVC tip in the SVC (normal ~70-75%); reflects balance between oxygen delivery and consumption.

At the bedside

  1. 1

    Measure CVP correctly

    Transducer at phlebostatic axis, zeroed; read at end-expiration at the base of the 'c' wave (or mean of 'a' wave). On a ventilator do not disconnect PEEP; interpret trend.

  2. 2

    Do not use CVP alone to give fluids

    A single CVP value does not predict fluid responsiveness. ESICM 2014: do not target any absolute CVP.

  3. 3

    Use CVP as a safety limit and diagnostic clue

    High or rising CVP (> 12-15 mmHg) with poor output suggests RV failure, tamponade, tension, fluid overload: stop fluids and look why. Low CVP (< 5) with hypotension makes hypovolaemia more likely.

  4. 4

    Sample ScvO2 correctly

    Slow draw from distal lumen of an SVC catheter (tip at cavo-atrial junction) after discarding dead space; analyse immediately.

  5. 5

    Interpret low ScvO2 (< 70%)

    Oxygen delivery inadequate for demand: low cardiac output, anaemia, hypoxaemia, or high consumption (fever, shivering, agitation). Consider fluids if responsive, inotrope, transfusion if Hb < 7 g/dL, oxygen, sedation/antipyretics.

  6. 6

    Interpret high ScvO2 (> 80%) with shock

    Does not mean adequate perfusion: suggests impaired extraction (late sepsis, microcirculatory shunting, cyanide, CO). Look at lactate, CO2 gap and peripheral perfusion.

Causes of abnormal ScvO2

Low ScvO2 (< 70%)High ScvO2 (> 80%)
Low cardiac output (hypovolaemia, cardiogenic)Microcirculatory shunting (late sepsis)
AnaemiaCytotoxic hypoxia (cyanide, CO)
HypoxaemiaHigh cardiac output states (liver failure)
High VO2: fever, shivering, seizures, agitationCatheter tip in RA near coronary sinus / sampling error
Red flag · call your senior now
Rising CVP with falling BP and urine output after fluids: stop fluids and scan the heart (RV failure, tamponade).
Pitfall
Giving fluid 'because CVP is 6'. Fluid decisions need dynamic tests (PLR, PPV) or a fluid challenge with stroke volume measurement.
Pitfall
Reading a normal ScvO2 as reassurance in septic shock with rising lactate.
Pearl
The 2001 EGDT trial targeted CVP 8-12 and ScvO2 ≥ 70%, but ProCESS, ARISE and ProMISe (PRISM meta-analysis 2017) found no benefit of protocolised EGDT over usual care.

References

  1. 1

    Cecconi M, De Backer D, Antonelli M, et al. Consensus on circulatory shock and hemodynamic monitoring. Task force of the European Society of Intensive Care Medicine. Intensive Care Med 2014;40:1795-815.

  2. 2

    Marik PE, Baram M, Vahid B. Does central venous pressure predict fluid responsiveness? A systematic review of the literature and the tale of seven mares. Chest 2008;134:172-8.

  3. 3

    Rivers E, Nguyen B, Havstad S, et al. Early goal-directed therapy in the treatment of severe sepsis and septic shock. N Engl J Med 2001;345:1368-77.

  4. 4

    PRISM Investigators. Early, goal-directed therapy for septic shock - a patient-level meta-analysis. N Engl J Med 2017;376:2223-34.

  5. 5

    Mallat J, Lemyze M, Tronchon L, Vallet B, Thevenin D. Use of venous-to-arterial carbon dioxide tension difference to guide resuscitation therapy in septic shock. World J Crit Care Med 2016;5:47-56.

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