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

GMCH Chandigarh - 2022

Medical & Surgical Nursing

Easy

Appeared in: GMCH Chandigarh - 2022

Explanation

Ringer's lactate is classified as an isotonic crystalloid solution.
Its osmolality (approximately 273 mOsm/L) is very close to the osmolality of human blood plasma (approximately 275-295 mOsm/L).
This similarity in concentration allows it to expand the extracellular fluid volume without causing significant water to shift between the intravascular space and the body's cells.
It is frequently used for fluid replacement in conditions such as dehydration, burns, and gastrointestinal fluid losses.

Option A: Dextrose in Normal Saline (e.g., D5NS) is a hypertonic solution. Its osmolality (around 560 mOsm/L) is significantly higher than that of plasma, causing water to move from the intracellular space into the extracellular space.
Option B: 10% Dextrose in water (D10W) is a hypertonic solution in the bag (around 505 mOsm/L). It provides free water and calories.
Option C: 45% NaCl, also known as half-strength normal saline, is a hypotonic solution. Its osmolality (around 154 mOsm/L) is lower than plasma, which causes fluid to shift from the extracellular space into the cells.

Visual 1: Chart - A comparative chart showing the tonicity (isotonic, hypotonic, hypertonic), osmolality, and common clinical uses of different IV fluids (e.g., 0.9% NS, LR, 0.45% NS, D5W, D10W, D5NS).
Visual 2: Diagram - An illustration showing the effect of isotonic, hypotonic, and hypertonic solutions on red blood cells, demonstrating no change, swelling/lysis, and crenation/shrinking, respectively.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Classification and Clinical Use of Intravenous (IV) Solutions as background academic context rather than a clinical decision trigger.
Administering the correct type of IV fluid is critical for patient safety. Using a hypotonic solution when an isotonic one is needed can lead to cellular swelling and hemolysis, while using a hypertonic solution can cause cellular dehydration and fluid overload.
Nurses must always verify the provider's order and understand the rationale for the chosen fluid. For example, Ringer's lactate is often preferred over Normal Saline in trauma or burn patients because its lactate content helps buffer metabolic acidosis.
What if? If a patient has severe liver disease, Ringer's lactate would be contraindicated. The liver is responsible for metabolizing lactate into bicarbonate. In liver failure, lactate can accumulate, worsening lactic acidosis. In this case, 0.9% Normal Saline would be a more appropriate isotonic choice.

How to Approach the Question

First, identify that the question asks for an 'isotonic' solution. Recall the definition of isotonic: a solution with a solute concentration similar to that of blood plasma.
Mentally categorize the common IV fluids based on their tonicity: isotonic, hypotonic, and hypertonic.
Recall that the two most common isotonic solutions are 0.9% Normal Saline (NS) and Ringer's Lactate (LR).
Evaluate each option against this knowledge:
Dextrose solutions (like 10% Dextrose) and combination solutions (like Dextrose + Normal Saline) are typically hypertonic in the bag.
Half-strength saline (0.45% NaCl) is hypotonic.

Concept Tested & Keywords

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