Which parameter best reflects the balance of oxygen delivery and consumption during anesthesia?

Which parameter best reflects the balance of oxygen delivery and consumption during anesthesia?

• A. SpO2
• B. SvO2
• C. End-tidal CO2
• D. Heart rate

Answer: (B)

The balance between oxygen delivery and consumption is best reflected by mixed venous oxygen saturation. This value shows how much oxygen remains after tissues have extracted what they need, so it directly indicates whether delivery is keeping up with demand. Arterial SpO2 only tells you how saturated the arterial blood is, not how much the tissues are using or how close you are to a shortfall. End-tidal CO2 reflects ventilation and CO2 removal, not the oxygen supply–demand balance. Heart rate can change with stress or analgesia but doesn’t quantify tissue oxygen extraction. SvO2 integrates delivery and consumption: it decreases when tissues extract more O2 or when delivery falls, and it increases when delivery exceeds consumption. In practice, SvO2 around normal mixed-venous range (roughly 65–75%) guides whether to optimize oxygen delivery (fluids, pumps, increasing FiO2/Hb) or acknowledge reduced metabolic demand.

The balance between oxygen delivery and consumption is best reflected by mixed venous oxygen saturation. This value shows how much oxygen remains after tissues have extracted what they need, so it directly indicates whether delivery is keeping up with demand. Arterial SpO2 only tells you how saturated the arterial blood is, not how much the tissues are using or how close you are to a shortfall. End-tidal CO2 reflects ventilation and CO2 removal, not the oxygen supply–demand balance. Heart rate can change with stress or analgesia but doesn’t quantify tissue oxygen extraction. SvO2 integrates delivery and consumption: it decreases when tissues extract more O2 or when delivery falls, and it increases when delivery exceeds consumption. In practice, SvO2 around normal mixed-venous range (roughly 65–75%) guides whether to optimize oxygen delivery (fluids, pumps, increasing FiO2/Hb) or acknowledge reduced metabolic demand.