What is the normal amount of sodium in serum?

Appeared in: Uttarakhand CHO - 2021

Explanation

The accepted normal range for serum sodium concentration in adults is 135-145 mmol/L (or mEq/L).
Sodium is the primary cation in the extracellular fluid and is the main determinant of extracellular osmolality.
This range signifies a state of homeostasis, which is crucial for maintaining proper fluid balance, nerve impulse transmission, and muscle function.
Values within this range indicate that the body's regulatory mechanisms for water and sodium are functioning correctly.

Option B: A sodium level of 155-165 mmol/L indicates moderate to severe hypernatremia (high sodium), which is a serious medical condition.
Option C: A sodium level of 145-155 mmol/L represents mild hypernatremia. Any value above 145 mmol/L is considered abnormal and indicates an imbalance.
Option D: A sodium level of 165-175 mmol/L indicates severe and life-threatening hypernatremia. This level can cause significant neurological damage, including seizures, coma, and brain hemorrhage.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Normal serum sodium levels and electrolyte balance as background academic context rather than a clinical decision trigger.
Nurses must be vigilant in monitoring serum sodium in at-risk patients, such as the elderly, infants, and those with heart failure, kidney disease, or receiving IV fluids or diuretics.
Early recognition of symptoms like confusion (hyponatremia) or lethargy (hypernatremia) is critical for prompt intervention and preventing severe outcomes.
What if? If a patient with chronic hyponatremia (e.g., 125 mmol/L) has their sodium corrected to 140 mmol/L in less than 12 hours, the nurse's priority is to assess for neurological changes like dysarthria, dysphagia, or paralysis, as this rapid correction can cause osmotic demyelination syndrome (ODS).

How to Approach the Question

Identify the question as a factual recall question asking for a specific, fundamental laboratory value.
Recognize the keywords "normal amount," "sodium," and "serum."
Recall the memorized normal ranges for common electrolytes. This is a core knowledge requirement for nursing.
Systematically evaluate the options. Any range starting above 145 mmol/L represents an abnormal, high value (hypernatremia).
Eliminate the options representing hypernatremia (145-155, 155-165, 165-175 mmol/L).
Select the option that matches the standard memorized range for normal serum sodium, which is 135-145 mmol/L.

Concept Tested & Keywords

QzW5M_07GP7en-fDRqKyUK

E6 Nursing Fundamentals Potter Perry 12e Part 5 p. 47-49

E6 Textbook of Biochemistry for medical StudentsDM Vasudevan Part 2 — Subpart A (pp 1-239 of 478) p. 94-96

E6 Nelson Textbook of Pediatrics(2024) — Volume 1 p. 534-536

Practise the full Uttarakhand CHO - 2021

Attempt every question from this paper in a timed mock, then review the full solution for each one.