SvO2 vs ScvO2
OVERVIEW
SvO₂ is Mixed Venous Oxygen Saturation whereas ScvO₂ is Central Venous Oxygen Saturation
- used as a measure of the adequacy of total body O₂ delivery
- both can be measured and displayed continuously in critical care settings:
- SvO₂ requires a pulmonary artery catheter (PAC)
- ScvO₂ requires a central venous catheter with the tip in the superior vena cava (SVC)
COMPARISON
| Feature | SvO₂ (Mixed Venous) | ScvO₂ (Central Venous) |
|---|---|---|
| Site | Pulmonary artery (PAC) | Superior vena cava (CVC) |
| Invasiveness | High (PAC required) | Lower (standard CVC) |
| Typical value | Slightly higher than ScvO₂ | Slightly lower than SvO₂ |
| Why | Includes SVC + IVC + coronary sinus IVC/ renal venous blood has high O₂ saturation | Reflects SVC only Excludes high‑saturation renal venous blood |
| When ScvO₂ > SvO₂ | High SO₂ in SVC: Anaesthesia (↑ CBF, ↓ metabolism) Brain injury Low SO₂ in IVC: Shock with splanchnic vasoconstriction | Same scenarios (driven by disproportionately low IVC saturation or high SVC saturation) |
| Clinical behaviour | Tracks global DO₂/VO₂ Less reliable in cardiogenic shock or severe regional hypoperfusion | Good surrogate in most distributive/hypovolaemic shock Less reliable in cardiogenic shock |
| Other data available | CO, PAP, temperature, derived indices | CVP only |
| Evidence | PAC: no mortality benefit; possible harm in some cohorts | Rivers EGDT (historical); Later trials show no benefit of ScvO₂‑targeted therapy in septic shock; Lactate clearance equivalent in septic shock |
| Complications | Higher (CVC complications plus PAC specific complications such as arrhythmia and PA rupture) | Lower (e.g. Line infection, thrombosis, pneumothorax) |
CONTRIBUTIONS OF CORONARY SINUS, SVC, AND IVC TO SvO₂
| Parameter | Coronary Sinus | SVC | IVC |
|---|---|---|---|
| % of CO | ~5% | ~25–30% | ~60–70% |
| Typical venous O₂ sat | 25–40% | 55–65% | 65–80% |
| O₂ extraction | Very high | High (brain) | Low (kidneys) |
| Effect on SvO₂ | Pulls ↓ | Sets ScvO₂ baseline | Pulls ↑ (dominant) |
| Effect on ScvO₂ | Minimal | Major | None (excluded) |
Critical Care
Compendium
Chris is an Intensivist and ECMO specialist at The Alfred ICU, where he is Deputy Director (Education). He is a Clinical Adjunct Associate Professor at Monash University, the Lead for the Clinician Educator Incubator programme, and a CICM First Part Examiner.
He is an internationally recognised Clinician Educator with a passion for helping clinicians learn and for improving the clinical performance of individuals and collectives. He was one of the founders of the FOAM movement (Free Open-Access Medical education) has been recognised for his contributions to education with awards from ANZICS, ANZAHPE, and ACEM.
His one great achievement is being the father of three amazing children.
On Bluesky, he is @precordialthump.bsky.social and on the site that Elon has screwed up, he is @precordialthump.
| INTENSIVE | RAGE | Resuscitology | SMACC
2 Comments
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Scvo2 should be higher than svo2 due to cardiac venous drainage which is very desaturated. I think the table is not correct
SVO2 is normally higher than SCVO2 because the blood flow contribution from the IVC is much greater than that of the coronary sinus.
Blood from the IVC includes blood from the kidneys, which normally have high blood flow and low O2 extraction – so that IVC blood has relatively higher SO2.
I’ve added a table to show this in the post.
Cheers
Chris