5% dextrose in 0.9% saline solution is - - RUHS, Jaipur, PB B.Sc Nursing Entrance-2023

RUHS, Jaipur, PB B.Sc Nursing Entrance-2023

Pharmacology

Medium

Appeared in: RUHS, Jaipur, PB B.Sc Nursing Entrance-2023

Explanation

5% dextrose in 0.9% saline (D5NS) is classified as a hypertonic solution.
Its combined osmolarity is approximately 560 mOsm/L, which is significantly higher than the normal osmolarity of blood plasma (about 275-295 mOsm/L).
This high solute concentration causes water to shift from the intracellular and interstitial spaces into the intravascular space.
Although the dextrose is metabolized in the body, leaving an isotonic solution, the fluid is always classified by its initial tonicity in the IV bag.

Option A: A hypotonic solution has a lower osmolarity than blood plasma, causing fluid to move into cells. D5NS has a much higher osmolarity.
Option C: An isotonic solution has an osmolarity similar to blood plasma. While D5NS has an isotonic component (0.9% saline), the addition of 5% dextrose makes the overall solution hypertonic.
Option D: A colloidal solution contains large molecules (like proteins or starches) that remain in the vascular space and draw fluid in. D5NS is a crystalloid solution, containing small molecules (glucose, sodium, chloride) that can pass through capillary membranes.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Classification of Intravenous (IV) Fluids based on Tonicity as background academic context rather than a clinical decision trigger.
Hypertonic solutions like D5NS are used for specific clinical purposes, such as providing calories, treating hyponatremia, or reducing cerebral edema by drawing fluid out of cells.
Nurses must administer hypertonic solutions with caution, as they can cause fluid volume overload and circulatory collapse if given too rapidly. The infusion site must be monitored closely for phlebitis and infiltration, as these solutions are irritating to the veins.
What if? If the solution were just 5% Dextrose in Water (D5W), it would be isotonic in the bag but become hypotonic in the body as the dextrose is metabolized. This is a key distinction from D5NS, where the remaining saline is isotonic.

How to Approach the Question

First, identify the core of the question, which is to determine the tonicity of a specific intravenous (IV) fluid.
Break down the IV fluid into its components: 5% dextrose and 0.9% saline.
Recall the properties of each component. 0.9% saline is isotonic. 5% dextrose adds a significant amount of solute (glucose).
Understand that combining these two components will result in a solution with a higher total solute concentration (osmolarity) than either component alone.
Compare the resulting solution's high osmolarity to the normal osmolarity of blood plasma (around 275-295 mOsm/L).
Conclude that since the solution's osmolarity is much higher than plasma's, it is classified as hypertonic.

Concept Tested & Keywords

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