Which one of the following is most likely to result in contraction alkalosis?
**Core Concept**
Contraction alkalosis is a type of metabolic alkalosis that occurs when there is a significant loss of hydrogen ions (H+) or gain of bicarbonate (HCO3-) from the extracellular fluid, leading to an increase in blood pH. This condition is often seen in scenarios where there is a sudden contraction in the extracellular fluid volume, such as after vomiting or excessive diuresis.
**Why the Correct Answer is Right**
During contraction alkalosis, the body attempts to conserve hydrogen ions and increase the extracellular fluid volume by activating the renin-angiotensin-aldosterone system (RAAS). This results in the release of aldosterone, which stimulates the kidneys to reabsorb sodium ions (Na+) and water, while excreting potassium ions (K+). The excess hydrogen ions that are not reabsorbed are excreted in the urine, leading to a decrease in blood pH. However, the kidneys also reabsorb more bicarbonate ions (HCO3-) from the filtrate, which further contributes to the development of metabolic alkalosis.
**Why Each Wrong Option is Incorrect**
**Option A:** This choice is incorrect because diabetic ketoacidosis (DKA) typically results in metabolic acidosis, not alkalosis. In DKA, the body produces excess ketone bodies, which are acidic in nature and lead to a decrease in blood pH.
**Option B:** This choice is incorrect because respiratory alkalosis occurs when there is an increase in ventilation, leading to a decrease in carbon dioxide (CO2) levels in the blood. This is not directly related to the contraction of extracellular fluid volume.
**Option C:** This choice is incorrect because hypokalemia (low potassium levels) can occur in contraction alkalosis, but it is not the primary cause of the condition.
**Clinical Pearl / High-Yield Fact**
It is essential to remember that contraction alkalosis can occur in any scenario where there is a significant loss of extracellular fluid volume, such as in patients with severe vomiting, diarrhea, or excessive diuresis.
**Correct Answer:** C.