Central venous oxygen saturation (ScvO2)

Reviewed and revised 15th November 2013


  • surrogate for SvO2 thus provides a surrogate measure of oxygen flux, reflecting the balance between oxygen delivery (DO2) and consumption (VO2).
  • was (controversially) advocated by the Surviving Sepsis Guidelines as part of early goal directed therapy for septic shock (target ScvO2 >70%)
  • may have a role in the management of postoperative patients


  • can be measured intermittently (venous gas) or continuously via a spectrophotometer
  • continuous systems typically have either:
    • a standard CVC with specialised fiberoptics on the tip (e.g. PreSep CVC, attaches to a Vigileo monitor), or
    • a fiberoptic line that can be fed down a lumen of a pre-existing CVC (e.g. CeVox, attaches to a PiCCO monitor)


Insertion and use

  • as per central line insertion
  • SvO2 monitor is either built in to the CVC or can be fed down a lumen in an already sited CVC
  • perform calibration

O2 flux = oxygen delivery (DO2) – oxygen consumption (VO2)

O2 flux = (cardiac output x (Haemoglobin concentration x SpO2 x 1.34) + (PaO2 x 0.003)) – VO2

Interpretation of scvO2

  • Normal oxygen extraction is 25–30% corresponding to a ScvO2 >65%
  • < 65% = Impaired tissue oxygenation
  • >80% = High PaO2; or suspect:
    • Cytotoxic dysoxia (e.g. cyanide poisoning, mitochrondial disease, severe sepsis)
    • Microcirculatory shunting (e.g. severe sepsis, liver failure, hyperthyroidism)
    • Left to right shunts



  • rarely used in Australasia (except as part of the ARISE trial)
  • response to therapy can be quickly observed when connected to a continuous spectrophotometer
  • studies in critical illness show that ScVO2 is consistently higher than SvO2 by approximately 5% (when averaged over multiple measurements) but parallels changes in response (e.g. to volume loading). i.e. changes in ScVO2 and SvO2 track one another, but the absolute values of one cannot be inferred from the other.
  • ScvO2 > 70% forms part of the strategy adopted in early goal directed therapy which showed a significant mortality reduction in sepsis (16%)
  • these patients often already have a CVL in situ (venous access, CVP monitoring)


  • recent data showing that lactate clearance in sepsis is non-inferior to continuous ScVO2 monitoring (Jones, JAMA, 2010)
  • titration of end of resuscitation to ScvO2 may not be required (ICU Monitor, 2010 – summary of Jones, JAMA, 2010)
  • ScvO2 does not reflect myocardial perfusion (upstream from the opening of the coronary venous sinus)

Difference between ScvO2 and SvO2

  • ScvO2 in anormal person is expected to be 2-3% less than SvO2 because it contains predominantly SVC blood from the upper body (ie. ScVO2 < SvO2)
    • blood from the upper body has a higher oxygen extraction ratio (OER), and thus a lower SO2 than IVC blood
    • the brain has high oxygen extraction ratio and the kidneys have the lowest, of the major organs at rest
  • However, the reverse relationship is often seen in critical illness. Situations where ScvO2 > SvO2:
    • decreased OER in SVC distribution
      • anaesthesia – because of increase in CBF and depression of metabolism
      • TBI or cerebral cooling – when cerebral metabolism depressed
    • decreased OER in IVC distribution
      • shock states – because of diversion of blood from splanchnic circulation and increased oxygen extraction and therefore IVC saturation decreases.


  • same as those associated with central line insertion
  • equipment failure
  • CeVox can block a CVC lumen completely and is prone to drift
  • Potential misinterpretation of the measured values if devices are incorrectly calibrated or malpositioned


Journal articles

  • Jones AE, Shapiro NI, Trzeciak S, Arnold RC, Claremont HA, Kline JA; Emergency Medicine Shock Research Network (EMShockNet) Investigators. Lactate clearance vs central venous oxygen saturation as goals of early sepsis therapy: a randomized clinical trial. JAMA. 2010 Feb 24;303(8):739-46. doi: 10.1001/jama.2010.158. PubMed PMID: 20179283; PubMed Central PMCID: PMC2918907.
  • Nebout S, Pirracchio R. Should We Monitor ScVO2 in Critically Ill Patients? Cardiol Res Pract. 2012;2012:370697. doi: 10.1155/2012/370697. Epub 2011 Sep 21. PubMed PMID: 21941671; PubMed Central PMCID: PMC3177360.
  • van Beest P, Wietasch G, Scheeren T, Spronk P, Kuiper M. Clinical review: use of venous oxygen saturations as a goal – a yet unfinished puzzle. Crit Care. 2011;15(5):232. doi: 10.1186/cc10351. Epub 2011 Oct 24. Review. PubMed PMID: 22047813; PubMed Central PMCID: PMC3334733.
  • Walley KR. Use of central venous oxygen saturation to guide therapy. Am J Respir Crit Care Med. 2011 Sep 1;184(5):514-20. doi: 10.1164/rccm.201010-1584CI. Review. PubMed PMID: 21177882. [Free Fulltext]

CCC 700 6

Critical Care


Chris is an Intensivist and ECMO specialist at the Alfred ICU in Melbourne. He is also a 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 three amazing children.

On Twitter, he is @precordialthump.

| INTENSIVE | RAGE | Resuscitology | SMACC


  1. Oxygen flux is actually the total amount of oxygen carried out of left ventricle in blood, in 1 minute.

  2. Hi. I hope you don’t mind me asking. In the other information (utility) part of the article, it says ScvO2 is consistently higher than SvO2; however, it was also stated in the article (in the Difference between ScvO2 and SvO2 part) that
    ScvO2 is normally < SvO2 because it contains predominantly SVC blood from the upper body. Thank you

    • Sorry, I agree that was confusing.
      Although there is some controversy about these measurements, I think the take home is that ScvO2 is expected to be 2-3% lover in “normal” people than SvO2.
      However, the opposite relationship is common in critical care (with SvO2 often higher than ScvO2 when measured) due to changes in regional blood flow and oxygen extraction (See examples provided in the text)
      Hope that helps

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