Which scenario would most likely decrease SvO2?

Which scenario would most likely decrease SvO2?

• A. Increased oxygen delivery due to fluids increasing preload
• B. Reduced oxygen consumption due to hypothermia
• C. Decreased cardiac output
• D. Increased arterial oxygen content due to supplemental oxygen

Answer: (C)

SvO2 reflects the balance between oxygen delivery to tissues and their oxygen use. Oxygen delivery depends on cardiac output and the arterial oxygen content. If preload is increased with fluids, cardiac output typically rises and more oxygen is delivered, so SvO2 tends to increase or stay normal. Lowering metabolic demand, as with hypothermia, reduces tissue oxygen consumption, which also tends to increase SvO2 because less O2 is extracted. Reducing cardiac output lowers delivery of O2 to tissues, so the tissues extract more of what is available and SvO2 falls. Increasing arterial oxygen content with supplemental oxygen raises delivery and pushes SvO2 higher. Therefore, the scenario that would most likely decrease SvO2 is decreased cardiac output.

SvO2 reflects the balance between oxygen delivery to tissues and their oxygen use. Oxygen delivery depends on cardiac output and the arterial oxygen content. If preload is increased with fluids, cardiac output typically rises and more oxygen is delivered, so SvO2 tends to increase or stay normal. Lowering metabolic demand, as with hypothermia, reduces tissue oxygen consumption, which also tends to increase SvO2 because less O2 is extracted. Reducing cardiac output lowers delivery of O2 to tissues, so the tissues extract more of what is available and SvO2 falls. Increasing arterial oxygen content with supplemental oxygen raises delivery and pushes SvO2 higher. Therefore, the scenario that would most likely decrease SvO2 is decreased cardiac output.