What is the average concentration of sodium chloride in an isotonic saline solution?

• A. 0.45%
• B. 0.75%
• C. 0.85%
• D. 1.0%

Answer: (C)

An isotonic saline solution is designed to have the same osmotic pressure as bodily fluids, such as blood plasma. The typical concentration of sodium chloride (NaCl) in an isotonic saline solution is around 0.85%. This concentration allows the solution to maintain osmotic balance when introduced into the body, ensuring that cells do not swell or shrink due to osmotic pressure differences.

Isotonic saline is commonly used in medical settings for hydration, drug delivery, and as a diluent for various laboratory tests. Understanding the correct concentration is essential for ensuring patient safety and the efficacy of treatments. Other concentrations listed, such as 0.45%, would be considered hypotonic and could lead to cell swelling, while 1.0% is hypertonic and could cause cell shrinkage. Therefore, recognizing 0.85% as the average concentration in an isotonic saline solution demonstrates an important aspect of clinical chemistry and fluid balance in medical practice.