Correct Answer: B

Rationale: This is incorrect because polyuria is a sign of hyponatremia, not hypernatremia. Polyuria is the excessive production of urine, which can cause fluid loss and sodium dilution. This is correct because dry mucous membranes are a sign of hypernatremia. Dry mucous membranes are caused by dehydration, which can occur in hypernatremia due to fluid shifting from the intracellular to the extracellular space. This is incorrect because diarrhea is a sign of hyponatremia, not hypernatremia. Diarrhea is the frequent and watery passage of stool, which can cause fluid and electrolyte loss. This is incorrect because intense thirst is a sign of both hyponatremia and hypernatremia. Intense thirst is a result of the body's attempt to restore fluid balance and osmolarity. This is incorrect because vomiting is a sign of both hyponatremia and hypernatremia. Vomiting is a reflex action that expels the contents of the stomach, which can cause fluid and electrolyte loss or imbalance.

Correct Answer: D

Rationale: Stroke is not a cause of hyponatremia, but rather a possible complication of it. Hyponatremia is a condition where the sodium level in the blood is too low, which can affect the brain function and cause symptoms such as confusion, seizures, or coma. Stroke is a condition where the blood supply to a part of the brain is interrupted, which can cause brain damage and neurological deficits. Dehydration is not a cause of hyponatremia, but rather a cause of hypernatremia. Dehydration is a condition where the body loses more fluids than it takes in, which can affect the blood volume and the electrolyte balance. Dehydration can cause hypernatremia, which is a condition where the sodium level in the blood is too high, which can also affect the brain function and cause symptoms such as thirst, dry mouth, or lethargy. Increased secretion of aldosterone is not a cause of hyponatremia, but rather a cause of hypokalemia. Aldosterone is a hormone that regulates the sodium and potassium levels in the body by increasing the reabsorption of sodium and the excretion of potassium in the kidneys. Increased secretion of aldosterone can cause hypokalemia, which is a condition where the potassium level in the blood is too low, which can affect the muscle and nerve function and cause symptoms such as weakness, cramps, or arrhythmias. Congestive heart failure (CHF) is a cause of hyponatremia, as it is a condition where the heart is unable to pump enough blood to meet the body's needs. This can lead to fluid retention and edema, which can dilute the sodium level in the blood and cause hyponatremia. CHF can also stimulate the release of antidiuretic hormone (ADH), which increases the reabsorption of water in the kidneys and further lowers the sodium level in the blood.

Correct Answer: D

Rationale: Intracellular to the extracellular fluid shift is not the cause of low blood pressure in this case. This fluid shift occurs when the cells lose water due to osmosis, such as in dehydration or hypernatremia. Interstitial to intravascular fluid shift is not the cause of low blood pressure in this case. This fluid shift occurs when the fluid moves from the tissue spaces to the blood vessels, such as in hypovolemia or hypotonic fluid administration. Interstitial to the intracellular fluid shift is not the cause of low blood pressure in this case. This fluid shift occurs when the fluid moves from the tissue spaces to the cells, such as in overhydration or hyponatremia. Intravascular to the interstitial fluid shift is the cause of low blood pressure in this case. This fluid shift occurs when the fluid moves from the blood vessels to the tissue spaces, such as in edema, inflammation, or increased capillary permeability. This reduces the blood volume and lowers the blood pressure.

Correct Answer: A

Rationale: This is correct because 3.5 to 5.0 mEq/L is the normal range of serum potassium level in adults. Potassium is an electrolyte that is important for nerve and muscle function, as well as acid-base balance. This is incorrect because 8.5 to 10.5 mg/dL is the normal range of serum calcium level in adults, not potassium. Calcium is an electrolyte that is involved in bone health, muscle contraction, and blood clotting. This is incorrect because 135 to 145 mEq/L is the normal range of serum sodium level in adults, not potassium. Sodium is an electrolyte that is essential for fluid balance, nerve transmission, and muscle contraction. This is incorrect because 1.8 to 2.6 mEq/L is the normal range of serum magnesium level in adults, not potassium. Magnesium is an electrolyte that is important for muscle and nerve function, as well as enzyme activity.

Correct Answer: B

Rationale: This is incorrect because 120 to 140 mEq/L is a low range for serum sodium, which indicates hyponatremia. Hyponatremia can cause confusion, lethargy, seizures, and coma. This is correct because 135 to 145 mEq/L is the normal range of serum sodium in adults. Sodium is essential for fluid balance, nerve transmission, and muscle contraction. This is incorrect because 150 to 160 mEq/L is a high range for serum sodium, which indicates hypernatremia. Hypernatremia can cause thirst, dry mouth, agitation, and convulsions. This is incorrect because 165 to 175 mEq/L is a very high range for serum sodium, which indicates severe hypernatremia. Severe hypernatremia can cause irreversible brain damage and death.