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Mixed venous oxgyen saturation

S_vO₂ = S_aO₂ - [VO₂ / (CO x 1.39 x Hb x10)]

• Normal value is 67 - 78% (ie. extraction ~25%)
• SvO2 <40% suggests a pre-terminal state
• Measure of cardiac output, perfusion and oxygenation
• Sampled from blood in the pulmonary artery (not adequate to sample SVC blood or RA blood because the blood from the coronary sinus is not adequately admixed)
• Peripheral venous blood sampling reflects perfusion/oxygenation in tissues and not a good indicator of cardiac output