Fluid & Electrolyte Q 77

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Normal serum sodium concentration ranges from:

  

    A. 120 to 125 mEq/L

    B. 125 to 130 mEq/L

    C. 136 to 145 mEq/L

    D. 140 to 148 mEq/L

    

    

Correct Answer: C. 136 to 145 mEq/L

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Normal serum sodium level ranges from 136 to 145 mEq/L. Sodium, which is an osmotically active anion, is one of the most important electrolytes in the extracellular fluid. It is responsible for maintaining the extracellular fluid volume, and also for regulation of the membrane potential of cells. Sodium is exchanged along with potassium across cell membranes as part of active transport.

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Option A: Sodium regulation occurs in the kidneys. The proximal tubule is where the majority of the sodium reabsorption takes place. In the distal convoluted tubule, sodium undergoes reabsorption. Sodium transport takes place via sodium-chloride symporters, which is by the action of the hormone aldosterone.

Option B: Among the electrolyte disorders, hyponatremia is the most frequent. Diagnosis is when the serum sodium level less than 135 mmol/L. Hyponatremia has neurological manifestations. Patients may present with headache, confusion, nausea, delirium.

Option D: Hypernatremia presents when the serum sodium levels greater than145 mmol/L. Symptoms of hypernatremia include tachypnea, sleeping difficulty, and feeling restless. Rapid sodium corrections can have serious consequences like cerebral edema and osmotic demyelination syndrome.

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