ScvO2 vs SvO2: Key Differences Every ICU Nurse Must Know
ScvO2 is the oxygen saturation of blood drawn from the superior vena cava via central line; SvO2 is the oxygen saturation of mixed venous blood taken from the pulmonary artery via Swan-Ganz catheter.
At 3 a.m. you’re staring at two numbers trending in opposite directions; one came from the triple-lumen in the IJ, the other from the PA port you never primed. The monitor alarms scream the same color, so the labels blur and you wonder why they aren’t identical.
Key Differences
ScvO2 reflects upper-body venous return, normally 5–10 % higher than SvO2. SvO2 averages all systemic venous blood and responds to global oxygen supply-demand. Sampling site, normal ranges, and clinical context differ.
Which One Should You Choose?
Use ScvO2 when a PA catheter is absent or contraindicated; trend it in sepsis resuscitation. Choose SvO2 for precise cardiac output calculations or when global oxygen flux is critical, accepting the catheter risks.
Can ScvO2 replace SvO2?
In sepsis protocols, yes—trends parallel closely. In cardiogenic shock, they diverge; SvO2 remains the gold standard.
Normal values?
ScvO2 70–80 %; SvO2 65–75 %. A sudden drop >5 % warrants immediate assessment.