A patient is admitted with signs of dehydration and hypovolemia. What is the primary purpose of administering an isotonic intravenous solution like 0.9% Sodium Chloride (Normal Saline)?

Appeared in: SCTIMST Staff Nurse - 2015 (Set-A)

Explanation

Isotonic solutions like 0.9% NaCl have a solute concentration similar to blood plasma.
This prevents any significant net movement of water between the intracellular and extracellular compartments.
As a result, the administered fluid remains in the extracellular space, primarily expanding the intravascular volume.
This action directly addresses the fluid deficit in hypovolemia, making it the first-line choice for volume resuscitation.

Option A: This describes the action of a hypotonic solution (e.g., 0.45% NaCl), which has a lower solute concentration than cells, causing water to move into the cells to rehydrate them.
Option C: This describes the action of a hypertonic solution (e.g., 3% NaCl), which has a higher solute concentration, pulling water out of cells and into the extracellular space.
Option D: 9% Sodium Chloride contains only sodium and chloride; it provides no calories or other nutrients.

Clinical Relevance

Nursing practice connection: Knowing Intravenous Fluid Therapy and Tonicity helps nurses interpret findings accurately and avoid errors in routine assessment, medication administration, and patient teaching.
For a patient with hypovolemia, the nurse's priority is to restore circulating volume to ensure adequate organ perfusion. Isotonic fluids are the standard of care for this initial resuscitation.
Nurses must monitor patients receiving IV fluids for signs of fluid volume overload, such as crackles in the lungs, shortness of breath, and peripheral edema, especially in patients with heart failure or kidney disease.
What if? If the patient's primary problem was severe hyponatremia (low sodium) with neurological symptoms, the answer would change. A hypertonic solution (like 3% NaCl) would be administered cautiously to draw water out of swollen brain cells and raise the serum sodium level.

How to Approach the Question

First, identify the patient's condition from the stem: 'dehydration and hypovolemia'. This means a loss of fluid volume, primarily from the extracellular space.
Next, identify the type of fluid mentioned: 'isotonic intravenous solution like 0.9% Sodium Chloride'.
Recall the definition of 'isotonic': having the same solute concentration as body fluids.
Connect the fluid type to the patient's condition. An isotonic fluid will stay where it's infused (the extracellular/intravascular space) without causing major fluid shifts.
Therefore, its primary purpose must be to increase the volume in that space.
Evaluate the options: Option B directly matches this reasoning. Options A and C describe hypotonic and hypertonic solutions, respectively. Option D is incorrect as saline has no calories.

Concept Tested & Keywords

Concept Tested: Intravenous Fluid Therapy and Tonicity
Stem keywords: dehydration, hypovolemia, isotonic intravenous solution, 0.9% Sodium Chloride, Normal Saline
Lead-in keywords: primary purpose
Clinical cues: Patient with signs of dehydration and hypovolemia, indicating a deficit in extracellular fluid volume.

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

E6 Gynecology Williams p. 50-74

Practise the full SCTIMST Staff Nurse - 2015 (Set-A)

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