Isotonic saline means, saline having a concentration of?

Appeared in: IGNOU Post B. SC. Nursing entrance-2019

Explanation

Isotonic saline has a solute concentration that is similar to the concentration of solutes in blood plasma, which is approximately 290-310 mOsm/L.
The standard concentration for isotonic sodium chloride (NaCl) solution, also called Normal Saline (NS), is 0.9%.
Because its concentration is similar to body fluids, administering 0.9% saline does not cause a significant net movement of water into or out of cells, making it ideal for fluid replacement.
It is the first-line choice for treating hypotensive patients with fluid volume deficit because it expands plasma volume effectively.

Option A: A 0.45% saline solution is hypotonic, not isotonic. It has a lower solute concentration than blood.
Option B: A 1.45% saline solution is hypertonic. It has a significantly higher solute concentration than blood.
Option C: A 1.5% saline solution is hypertonic. Its concentration is higher than that of body fluids.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Definition and concentration of isotonic saline as background academic context rather than a clinical decision trigger.
Understanding IV fluid tonicity is fundamental for safe nursing practice. Administering the wrong type of fluid can cause dangerous fluid shifts and electrolyte imbalances.
Isotonic fluids (0.9% NaCl, Lactated Ringer's) are the go-to for initial resuscitation in most cases of hypovolemia (e.g., from hemorrhage, sepsis, or dehydration) because they quickly expand the intravascular volume.
A nurse must always monitor patients receiving IV fluids for signs of fluid overload (e.g., crackles in the lungs, edema, shortness of breath), especially those with heart or kidney disease.

How to Approach the Question

First, identify the key term in the question: 'Isotonic saline'.
This is a factual recall question. Access your knowledge about the classification of intravenous fluids.
Recall the definition of 'isotonic': a solution having the same osmotic pressure as some other solution, especially one in a cell or a body fluid.
Remember the standard concentrations for saline solutions: 0.9% is 'normal' or isotonic, less than 0.9% is hypotonic, and greater than 0.9% is hypertonic.
Evaluate the options based on this knowledge. 0.45% is hypotonic. 1.45% and 1.5% are hypertonic.
Conclude that 0.9% is the correct concentration for isotonic saline.

Concept Tested & Keywords

QNY_iD08iL9ByU4omjtcvM

E6 Pharmacology Nursing Lilley 11e Part 2 p. 161-163

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

E6 Medicine Davidson Principles Practice 24e p. 757-759

Practise the full IGNOU Post B. SC. Nursing entrance-2019

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