Base excess quantifies the amount of acid/base needed to return blood pH to normal. Which option matches this definition?

Base excess quantifies the amount of acid/base needed to return blood pH to normal. Which option matches this definition?

• A. It reflects oxygen carrying capacity
• B. It measures the dissolved CO2 in plasma
• C. It quantifies the amount of acid/base needed to return blood pH to normal
• D. It indicates the bicarbonate concentration

Answer: (C)

Base excess is a measure of how much strong acid or base would need to be added to blood to bring the pH back to normal under standard conditions. This makes it a direct reflection of the metabolic component of acid–base balance—the buffering capacity of the blood. A positive base excess means there is excess base (base surplus), pointing to metabolic alkalosis or compensation for a respiratory acidosis, while a negative base excess indicates a base deficit, consistent with metabolic acidosis or compensation for a respiratory alkalosis. The other options describe different things: dissolved CO2 or oxygen-carrying capacity, or bicarbonate concentration, but they do not define the amount of acid/base required to normalize pH.

Base excess is a measure of how much strong acid or base would need to be added to blood to bring the pH back to normal under standard conditions. This makes it a direct reflection of the metabolic component of acid–base balance—the buffering capacity of the blood. A positive base excess means there is excess base (base surplus), pointing to metabolic alkalosis or compensation for a respiratory acidosis, while a negative base excess indicates a base deficit, consistent with metabolic acidosis or compensation for a respiratory alkalosis. The other options describe different things: dissolved CO2 or oxygen-carrying capacity, or bicarbonate concentration, but they do not define the amount of acid/base required to normalize pH.