Which of the following is an example of an isotonic intravenous solution?

Appeared in: DSSSB 6 September 2024

Explanation

9% Sodium Chloride, also known as Normal Saline (NS), is an isotonic solution.
It has an osmolarity of approximately 308 mOsm/L, which is very close to the osmolarity of human blood plasma (about 280-300 mOsm/L).
Because its concentration is similar to body fluids, it expands the extracellular fluid volume without causing a significant shift of water into or out of the body's cells.
It is commonly used for fluid resuscitation in hypovolemic states, shock, and for patients with diabetic ketoacidosis.

Option A: 45% Sodium Chloride (Half-Normal Saline) is a hypotonic solution, not isotonic. Its osmolarity is about 154 mOsm/L, which is lower than that of plasma.
Option C: 3% Sodium Chloride is a hypertonic solution. Its osmolarity is very high (1026 mOsm/L), causing it to pull fluid from the intracellular space into the vascular compartment.
Option D: 10% Dextrose in water (D10W) is a hypertonic solution in the bag due to its high concentration of dextrose. Although the dextrose is metabolized in the body, its initial effect is hypertonic.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Classification of intravenous (IV) solutions based on tonicity as background academic context rather than a clinical decision trigger.
Choosing the correct IV fluid is a critical nursing responsibility. Administering the wrong type of fluid can lead to serious complications.
For example, giving a hypertonic solution to a patient with cellular dehydration can worsen the condition. Conversely, giving a hypotonic solution to a patient with cerebral edema can increase intracranial pressure.
Nurses must always verify the healthcare provider's order, understand the rationale for the chosen fluid, and monitor the patient for signs of fluid imbalance, such as edema, shortness of breath, or changes in blood pressure.

How to Approach the Question

First, identify the core concept of the question, which is 'isotonic intravenous solution'.
Recall the definition of an isotonic solution: a fluid with a solute concentration similar to that of blood plasma, which does not cause a net fluid shift across cell membranes.
Remember the benchmark for isotonic saline: 0.9% Sodium Chloride (Normal Saline).
Evaluate each option against this benchmark:
Is 0.45% less than or greater than 0.9%? It's less, so it's hypotonic.
Is 3% less than or greater than 0.9%? It's greater, so it's hypertonic.

Concept Tested & Keywords

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E6 Nursing Brunner Adult Health 3SA Vol 1 Part 1 p. 142-144

E6 Nursing Fundamentals Potter Perry 12e Part 5 p. 68-70

Practise the full DSSSB 6 September 2024

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