Correct Answer: C

Rationale: The correct answer is C because taking sodium bicarbonate after every meal can actually increase the risk of metabolic alkalosis due to its alkaline nature. Sodium bicarbonate can lead to an excessive build-up of bicarbonate in the bloodstream, causing alkalosis. Choice A is not directly related to metabolic alkalosis. Choice B, taking digoxin, is unrelated to metabolic alkalosis as well. Choice D, drinking six glasses of water due to sweating, does not contribute to metabolic alkalosis as it helps maintain hydration and electrolyte balance.

Correct Answer: C

Rationale: The correct answer is C: Help distinguish reduced renal blood flow from decreased renal function. Rationale: 1. Oliguria is a decrease in urine output. 2. Fluid challenge with normal saline can help determine the cause of oliguria by assessing the response of the kidneys. 3. If the oliguria improves after the fluid challenge, it suggests reduced renal blood flow as the cause. 4. If oliguria persists, it indicates decreased renal function. Summary: A. Fluid challenge does not directly help in distinguishing between hyponatremia and hypernatremia. B. Evaluating pituitary gland function requires specific tests, not just a fluid challenge. D. Treating hypertension-induced oliguria may involve different interventions, not just a fluid challenge.

Correct Answer: D

Rationale: The correct answer is D: Increased conservation of sodium. Older adults tend to have an increased conservation of sodium, leading to fluid retention and decreased fluid intake, which can contribute to dehydration. A: Decreased kidney mass is incorrect because it is a factor that can contribute to decreased kidney function but not directly linked to dehydration. B: Decreased renal blood flow can impact kidney function but is not a direct cause of dehydration in older adults. C: Decreased excretion of potassium is not a factor that directly contributes to dehydration in older adults.

Correct Answer: B

Rationale: The correct answer is B: Respiratory alkalosis. Hyperventilation leads to excessive elimination of carbon dioxide, causing a decrease in PaCO2 levels, resulting in respiratory alkalosis. This is the most common cause of hyperventilation. Respiratory acidosis (choice A) occurs when there is retention of carbon dioxide. Increased PaCO2 (choice C) is a consequence of respiratory acidosis, not alkalosis. CNS disturbances (choice D) can lead to abnormal breathing patterns but are not the most common cause of hyperventilation.

Correct Answer: A

Rationale: The correct answer is A: Increased serum sodium. High serum sodium levels trigger the release of antidiuretic hormone (ADH) from the pituitary gland to help retain water in the body and maintain fluid balance. This is a physiological response to prevent further dehydration. Decreased serum potassium (choice B), decreased hemoglobin (choice C), and increased platelets (choice D) do not directly stimulate the release of ADH. Hence, they are incorrect choices in this scenario.