II. Definitions
- Central Venous Oxyhemoglobin Saturation (ScvO2)
- Oyxgen saturation from catheter at internal jugular or subclavian vein
- Represents oxygen still bound to Hemoglobin After passing through tissue
- Normally >68% (correlates with SvO2 which is typically 2-3% lower)
- In shock, ScvO2 may be 5-7% higher than SvO2
- Mixed Venous Oxyhemoglobin Saturation (SvO2)
- Oxygen Saturation from pulmonary artery catheter (wedge pressure) reading
- Normally >65%
III. Physiology: Indirect measures of tissue Oxygen Consumption
- Serum Lactic Acid
- Forms in response to tissue Hypoxia during anaerobic metabolism
- Many factors affect Lactic Acid. See Lactic Acid for causes of elevation
- Organ dysfunction
- ScvO2 (or SvO2)
- Difference between SaO2 and ScvO2 represents tissue Oxygen Consumption
- Normal levels do not exclude hypoperfusion
IV. References
- Killu and Sarani (2016) Fundamental Critical Care Support, p. 93-114