Fluid & Electrolyte Q 22

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Aldosterone secretion in response to fluid loss will result in which one of the following electrolyte imbalances?

  

    A. Hypokalemia

    B. Hyperkalemia

    C. Hyponatremia

    D. Hypernatremia

    

    

Correct Answer: A. Hypokalemia

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Aldosterone is secreted in response to fluid loss. Aldosterone causes sodium reabsorption and potassium elimination, further exacerbating hypokalemia. Aldosterone causes sodium to be absorbed and potassium to be excreted into the lumen by principal cells. In alpha intercalated cells, located in the late distal tubule and collecting duct, hydrogen ions and potassium ions are exchanged. Hydrogen is excreted into the lumen, and the potassium is absorbed.

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Option B: The most common cause of hyperkalemia is pseudohyperkalemia, which is not reflective of the true serum potassium levels. Pseudohyperkalemia is most commonly due to hemolysis of the sample causing intracellular potassium to be measured in the serum. Metabolic acidosis may cause intracellular potassium to shift into the extracellular space without red cell injury. Metabolic acidosis is most frequently caused by decreased, effective, circulating, arterial blood volume.

Option C: Physiological stimuli that cause vasopressin release in adjunct with increased fluid intake can cause hyponatremia. Hypothyroidism and adrenal insufficiency may contribute to an increased release of vasopressin. Physiological stimuli for vasopressin release include loss of intravascular volume (hypovolemic hyponatremia) and the loss of effective intravascular volume (hypervolemic hyponatremia).

Option D: The basic mechanisms of hypernatremia are water deficit and excess solute. Total body water loss relative to solute loss is the most common reason for developing hypernatremia. Hypernatremia is usually associated with hypovolemia, which can occur in conditions that cause combined water and solute loss, where water loss is greater than sodium loss, or free water loss.

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