Which option below causes metabolic acidosis?

Choice A: Hypoventilation

Hypoventilation refers to inadequate ventilation that leads to an increased concentration of carbon dioxide (CO2) in the blood, resulting in respiratory acidosis. This condition is characterized by a decrease in blood pH due to the accumulation of CO2, which forms carbonic acid. Hypoventilation does not cause metabolic acidosis, as it primarily affects the respiratory component of acid-base balance.

Choice B: Massive Blood Transfusion

Massive blood transfusion can lead to metabolic alkalosis rather than metabolic acidosis. This is because stored blood products often contain citrate, which is metabolized to bicarbonate in the liver, increasing the blood’s alkalinity. Additionally, the transfusion of large volumes of blood can dilute the plasma bicarbonate concentration, but this typically does not result in metabolic acidosis.

Choice C: Kidney Failure

Kidney failure is a common cause of metabolic acidosis. The kidneys play a crucial role in maintaining acid-base balance by excreting hydrogen ions (H+) and reabsorbing bicarbonate (HCO3-). When the kidneys fail, they are unable to remove sufficient acids from the blood, leading to an accumulation of metabolic acids and a decrease in blood pH. This condition is known as metabolic acidosis and can result from chronic kidney disease (CKD) or acute kidney injury (AKI).

Choice D: Hyperventilation

Hyperventilation leads to respiratory alkalosis, not metabolic acidosis. This condition occurs when there is excessive ventilation, causing a decrease in CO2 levels in the blood and an increase in blood pH. Hyperventilation reduces the concentration of carbonic acid, leading to an alkaline state. It does not contribute to metabolic acidosis, which involves an imbalance in the metabolic components of acid-base regulation.

Choice A Reason:

Boxed warnings, also known as black box warnings, are the strictest warnings put in the labeling of prescription drugs by the FDA when there is reasonable evidence of an association of a serious hazard with the drug. However, they do not necessarily indicate that a drug should only be given in life-threatening circumstances. Instead, they highlight the potential for serious or life-threatening risks and advise on how to use the drug safely.

Choice B Reason:

While some boxed warnings may include information about teratogenic effects (effects that can cause birth defects), this is not their primary purpose. Boxed warnings are broader and can apply to various serious risks, not just teratogenicity. Therefore, this choice is too narrow to be correct.

Choice C Reason:

This is the correct answer. Boxed warnings are designed to alert prescribers to serious or life-threatening risks associated with a drug and provide guidance on how to mitigate these risks. This can include recommendations for monitoring, dosage adjustments, or avoiding certain populations. The goal is to ensure that prescribers are fully aware of the risks and can take appropriate measures to minimize harm to patients.

Choice D Reason:

Boxed warnings do not typically provide information about antidotes for toxicity. While managing toxicity is an important aspect of drug safety, boxed warnings focus on alerting prescribers to serious risks and how to mitigate them, rather than detailing specific antidotes.