Nursing fluids and electrolytes practice questions
Fifteen questions on IV fluids, electrolyte imbalances, ECG changes and fluid status. Pick an answer to see the explanation.
Written by the Quizard team. Last updated
Exam questions in this area usually give you a lab value and ask for the sign or the action that goes with it. Reference ranges vary between laboratories and textbooks, so learn the ones your course uses. This set focuses on patterns that hold across them.
| Fluid | Tonicity |
|---|---|
| 0.9% sodium chloride | Isotonic |
| Lactated Ringer’s | Roughly isotonic |
| 0.45% sodium chloride | Hypotonic |
| 3% sodium chloride | Hypertonic |
| 5% dextrose in water | Isotonic in the bag, acts as hypotonic in the body |
Questions
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1. How is 0.9% sodium chloride classified?
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Answer: Isotonic. It is close to the osmolality of plasma, so it stays mainly in the extracellular space.
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2. Which of these is a hypotonic IV fluid?
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Answer: 0.45% sodium chloride. 0.45% saline has a lower osmolality than plasma, so water moves into cells.
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3. Why does D5W act as a hypotonic fluid in the body?
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Answer: The dextrose is metabolized, leaving free water. Once the glucose is used, what remains is water.
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4. Which ECG change is classically linked to hypokalemia?
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Answer: Prominent U waves. Flattened T waves and U waves are typical of low potassium.
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5. Which ECG change is classically linked to hyperkalemia?
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Answer: Tall peaked T waves. Peaked T waves can progress to a wide QRS and dangerous arrhythmias.
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6. How should IV potassium chloride be given?
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Answer: Diluted and by controlled infusion, never as an IV push. An IV push can cause fatal cardiac arrest.
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7. Which treatment stabilizes the heart first in severe hyperkalemia with ECG changes?
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Answer: IV calcium gluconate. Calcium protects the myocardium but does not lower potassium. Insulin with dextrose then shifts potassium into cells.
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8. Chvostek’s and Trousseau’s signs suggest which imbalance?
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Answer: Hypocalcemia. Low calcium increases neuromuscular excitability.
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9. What is the main risk of correcting chronic hyponatremia too quickly?
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Answer: Osmotic demyelination. Rapid shifts can damage neurons, so sodium is raised gradually.
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10. Hypokalemia that does not respond to replacement should prompt a check of which level?
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Answer: Magnesium. Low magnesium makes it hard to correct low potassium.
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11. Which finding is an early sign of magnesium sulfate toxicity?
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Answer: Loss of deep tendon reflexes. Reflexes are lost before respiratory depression, so they are monitored during infusion.
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12. What is the antidote for magnesium sulfate toxicity?
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Answer: Calcium gluconate. Calcium gluconate counters the effects of magnesium.
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13. A patient gains 2 kg overnight. About how much fluid does this suggest?
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Answer: 2 L. One kilogram of body weight is about one liter of fluid, which is why daily weights are useful.
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14. Which group of findings suggests fluid overload?
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Answer: Crackles, distended neck veins and edema. Excess volume backs up into the lungs and the venous system.
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15. What is the main intracellular cation?
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Answer: Potassium. Potassium is mainly inside cells, while sodium is the main extracellular cation.
For exam study only, not clinical guidance. Doses, reference ranges and protocols vary, so follow your course, your local policy and current references. Spotted a mistake? Tell us.
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