0.45 percent saline is a/an?

UPRVUNL - 2021

Medical & Surgical Nursing

Easy

Appeared in: UPRVUNL - 2021

Explanation

45% saline, or half-normal saline, has a lower solute concentration (osmolarity of ~154 mOsm/L) compared to blood plasma (~275-295 mOsm/L).
Due to this lower concentration, it is classified as a hypotonic solution.
When administered, hypotonic solutions cause water to shift from the intravascular space into the intracellular space to achieve equilibrium, leading to cellular hydration or swelling.

Option A: The term 'Semi-isotonic' is not a standard medical classification for intravenous fluids. Solutions are categorized based on their tonicity relative to plasma as hypotonic, isotonic, or hypertonic.
Option B: Isotonic solutions have an osmolarity similar to blood plasma. The standard isotonic saline solution is 0.9% NaCl (Normal Saline). Since 0.45% is half the concentration of 0.9%, it is not isotonic.
Option C: Hypertonic solutions have a higher osmolarity than blood plasma, causing water to move out of cells. Examples include 3% or 5% NaCl. 0.45% saline has a lower, not higher, concentration.

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.
Hypotonic solutions like 0.45% saline are used to treat cellular dehydration, such as in diabetic ketoacidosis (DKA) after initial stabilization with isotonic fluids.
A critical nursing responsibility is to monitor for cerebral edema when administering hypotonic fluids, as the fluid shift into brain cells can increase intracranial pressure (ICP). Watch for changes in level of consciousness, pupillary changes, and headache.
What if? If a patient has a head injury or is at risk for increased ICP, administering a hypotonic solution like 0.45% saline is contraindicated. It would worsen cerebral edema. In such cases, an isotonic or even a hypertonic solution would be indicated to manage fluid balance without increasing brain swelling.

How to Approach the Question

First, identify the core of the question, which is to classify '0.45 percent saline' based on its tonicity.
Recall the benchmark for saline solutions: 0.9% NaCl is known as 'Normal Saline' and is the standard isotonic solution.
Compare the given concentration (0.45%) to the isotonic standard (0.9%). Since 0.45% is less than 0.9%, the solution has a lower solute concentration.
Relate the concentration to the correct terminology: 'hypo-' means 'less than' or 'under'. Therefore, a solution with a lower concentration than plasma is hypotonic.
Eliminate the other options. 'Isotonic' refers to 0.9% saline. 'Hypertonic' refers to solutions with concentrations greater than 0.9% (e.g., 3% saline). 'Semi-isotonic' is not a standard term.

Concept Tested & Keywords

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