Isotonic NS contains ... sodium per 100 ml?

Appeared in: ESIC Nursing Officer 2016 (Shift -2)

Explanation

Isotonic Normal Saline (NS) is defined as a 0.9% solution of sodium chloride (NaCl).
The concentration '% w/v' (weight by volume) signifies the number of grams of a substance in 100 mL of solution.
Therefore, a 0.9% solution contains exactly 0.9 grams of sodium chloride in every 100 mL of fluid.
Although the question asks for 'sodium', the options refer to the weight of the entire sodium chloride compound, which is standard clinical convention for this type of question.

Option A: This value is incorrect in both magnitude and unit. It is 10,000 times smaller than the actual amount.
Option B: This value uses the wrong unit (milligrams instead of grams). It is 1,000 times smaller than the correct amount.
Option C: This amount would create a 0.09% solution. This is a hypotonic solution, sometimes referred to as quarter-normal saline, not an isotonic one.

Visual 1: Infographic: A visual comparison of Isotonic (0.9% NaCl), Hypotonic (0.45% NaCl), and Hypertonic (3% NaCl) solutions, showing their effect on red blood cells (no change, swelling, and shrinking, respectively).

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Composition and Concentration of Isotonic Normal Saline as background academic context rather than a clinical decision trigger.
Normal Saline is the most frequently used crystalloid solution for intravenous fluid resuscitation to expand extracellular fluid volume in conditions like dehydration, shock, and hemorrhage.
Nurses must be vigilant for signs of fluid overload (e.g., lung crackles, edema) when administering any isotonic fluid, especially in patients with cardiac or renal compromise.
What if? If a patient required fluid to treat cellular dehydration (to move water into cells), a hypotonic solution like 0.45% NaCl ('half-normal saline') would be used instead of isotonic NS.

How to Approach the Question

First, identify the key term in the question: 'Isotonic NS'.
Recall the standard definition of Isotonic Normal Saline, which is a 0.9% sodium chloride solution.
Understand the convention for percentage solutions in medicine: '% w/v' means 'grams per 100 mL'.
Directly apply this rule: 0.9% means 0.9 grams per 100 mL.
Scan the options to find the one that matches this calculation (0.9 gm) and verify the units.

Concept Tested & Keywords

Q7nBp8DKUM4Z9rsnJa8dkf

Practise the full ESIC Nursing Officer 2016 (Shift -2)

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