Which one among the following is a physiologically hypertonic solution?

ESIC Nursing Officer-7July 2024

Nursing Foundation

Easy

Appeared in: ESIC Nursing Officer-7July 2024

Explanation

A hypertonic solution has a higher solute concentration (osmolality) than the body's cells and blood plasma.
3% sodium chloride has an osmolality of approximately 1026 mOsm/L, which is significantly higher than the normal plasma osmolality of about 275-295 mOsm/L.
When administered, 3% NaCl creates a strong osmotic gradient that pulls water out of the body's cells and into the bloodstream.
This effect causes cells to shrink and expands the intravascular volume.

Option B: 9% sodium chloride, also known as Normal Saline (NS), is an isotonic solution. Its osmolality (approx. 308 mOsm/L) is similar to that of blood plasma, so it does not cause a significant net movement of water into or out of cells.
Option C: 45% sodium chloride, or Half-Normal Saline, is a hypotonic solution. Its osmolality (approx. 154 mOsm/L) is lower than that of blood plasma. It causes fluid to shift from the bloodstream into the cells.
Option D: 5% dextrose in water (D2.5W) is a hypotonic solution. Although it contains sugar, the dextrose is quickly metabolized by the body, leaving behind free water which then moves into cells. Its initial osmolality is already low (approx. 126 mOsm/L).

Visual 1: Diagram: 'Effect of Tonicity on Red Blood Cells'. This visual should show a red blood cell in three states: in an isotonic solution (normal), in a hypotonic solution (swollen/lysed), and in a hypertonic solution (shrunken/crenated). This directly illustrates the concept tested.
Visual 2: Chart: 'Comparison of Common IV Fluids'. A chart listing various IV fluids (0.9% NaCl, 0.45% NaCl, 3% NaCl, D5W, Lactated Ringer's) with their tonicity, osmolality, and primary clinical use would be a helpful study aid.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Tonicity of Intravenous (IV) Solutions as background academic context rather than a clinical decision trigger.
Understanding IV fluid tonicity is a fundamental nursing responsibility for safe medication administration. Administering the wrong type of fluid can lead to serious complications like cerebral edema, fluid overload, or cellular dehydration.
Nurses must meticulously monitor patients receiving hypertonic saline for signs of fluid overload (e.g., pulmonary edema, hypertension) and neurological changes. Rapid changes in serum sodium can cause severe, irreversible brain damage.
What if? If a patient with a head injury and increased intracranial pressure were mistakenly given a hypotonic solution like 0.45% NaCl instead of a hypertonic one, the hypotonic fluid would shift into the brain cells, worsening cerebral edema and potentially leading to brain herniation.

How to Approach the Question

First, understand the question's core concept: 'physiologically hypertonic solution'. This requires recalling the definition of tonicity.
Define the three types of tonicity: Isotonic (same concentration as blood), Hypotonic (lower concentration), and Hypertonic (higher concentration).
Recall or look up the standard tonicity for common IV fluids. A key benchmark is that 0.9% NaCl is isotonic.
Evaluate each option against the benchmark: Is the concentration higher or lower than 0.9% NaCl? For dextrose solutions, remember that the body metabolizes the sugar, leaving free water, which makes them effectively hypotonic.
Identify that 3% is a much higher concentration of sodium chloride than the isotonic 0.9%, making it hypertonic.
Select the option that fits the definition of hypertonic.

Concept Tested & Keywords

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