II. Definitions

  1. Central Venous Oxyhemoglobin Saturation (ScvO2)
    1. Oyxgen saturation from catheter at internal jugular or subclavian vein
    2. Represents oxygen still bound to Hemoglobin After passing through tissue
    3. Normally >68% (correlates with SvO2 which is typically 2-3% lower)
    4. In shock, ScvO2 may be 5-7% higher than SvO2
  2. Mixed Venous Oxyhemoglobin Saturation (SvO2)
    1. Oxygen Saturation from pulmonary artery catheter (wedge pressure) reading
    2. Normally >65%

III. Physiology: Indirect measures of tissue Oxygen Consumption

  1. Serum Lactic Acid
    1. Forms in response to tissue Hypoxia during anaerobic metabolism
    2. Many factors affect Lactic Acid. See Lactic Acid for causes of elevation
  2. Organ dysfunction
  3. ScvO2 (or SvO2)
    1. Difference between SaO2 and ScvO2 represents tissue Oxygen Consumption
    2. Normal levels do not exclude hypoperfusion

IV. References

  1. Killu and Sarani (2016) Fundamental Critical Care Support, p. 93-114

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