Please help me understand ScvO2 in Sepsis
- 0Jan 1, '13 by cluv2nurseNew ICU nurse at a major teaching hospital, can someone please explain to me the reason for high in low values of ScvO2 in septic patients, I have ED experience but hemodynamic number monitoring is new to me.
- 4,943 Views
- 5Jan 1, '13 by CrufflerJJFirst off, here are a couple decent webpages you might want to review:
Multi-Center Study of Central Venous Oxygen Saturation (ScvO2) as a Predictor of Mortality in Patients with Sepsis
Surviving Sepsis Campaign
In early sepsis, you'll frequently see a hyperdynamic phase. During this phase, heart rate & cardiac output are increased, in an attempt to maintain adequate perfusion/oxygen supply to tissues.
ScVO2 normally runs ~71-89% (first webpage listed above). If your pt's ScVO2 is low, there are several possible approaches to increasing oxygen delivered to the tissues:
- Ensure that your pt has an adequate circulating volume (as directed by CVP or a FloTrac SVV number) - give crystalloids or
colloids if needed
- Increase FiO2 (increase oxygen percentage inspired by the pt)
- Increase Hematocrit (transfuse more oxygen carrying red blood cells)
- If circulating volume, FiO2, and HCT are decent, then consider adding an inotrope such as dobutamine to increase cardiac output
In later sepsis, things are shutting down. Tissue & organs are dying, thus not using available oxygen circulated to them. This is a "bad thing", and may be more lethal than a low ScVO2 (again, see NIH paper).
Goes into some interesting theories as to WHY hyperoxia occurs in sepsis (impairment in microcirculatory blood flow vs mitochondrial dysfunction), the theory that excessive oxygen may be harmful in sepsis pts, and one approach to try and "kick start" dysfunctional mitochondria.
- 2Jan 2, '13 by CrufflerJJQuote from Esme12The book (available on the icufaqs.com website at Notes on ICU Nursing: FAQ Files from the MICU: Second Edition by Mark Hammerschmidt (Author) ) is a most excellent reference for newbie and experienced ICU folks. Lots & lots of info. A great book, written from a real world perspective.You will like this source...icufaqs.org there is a lot more information than just SVO2 I think you will find it helpful.Last edit by CrufflerJJ on Jan 3, '13
- 3Jan 4, '13 by detroitdanoSomeone asked this a while back, here was my response.
Low SvO2 means the entire body is extracting more oxygen than normal from the blood. High means your body is taking less oxygen from the blood because the vessels are so clamped down they cannot get oxygen into the tissues.
Lactic acid is a byproduct of anaerobic metabolism, when the tissues have used up all the oxygen it can during aerobic metabolism. Everyone has what they call a normal SvO2 but for me it's 60-75%. That means 25-40% of the oxygen pumped out by your heart is being used by the body, 60-75% of the circulated oxygen makes it way back without being utilized. If your SvO2 is, for example, 55, you might not see anaerobic metabolism. Your body is just extracting more oxygen for normal function. At 30 or 40, you're likely going to see anaerobic metabolism and a concurrent rise in lactate or even lactic acidosis.
You can also see a rise in lactate without a drop in SvO2 for many other reasons (i.e. tissue death, respiratory distress, etc.), so you have to know the whole picture to utilize either the SvO2 or lactate properly to treat your patient.
Also understand that ScvO2 and SvO2 aren't the same thing, technically.
ScvO2 means venous sat readings from the blood before it returns to the right atrium, in your superior vena cava. PA catheter/mixed venous sats measures downstream from where the ScvO2 is taken, past the right atrium, where blood from the coronary sinus has "mixed" with blood returned from the rest of the body.
Your heart sucks up a lot of oxygen, so the coronary sinus blood has a lower SvO2, let's say the sat is 30%. Mix that with blood with a sat of 60%. The combined, mixed sat, will be less than 60% now.