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OMSB Renal, Fluids & Electrolytes Practice Questions
This topic combines fluid balance, electrolyte imbalances and kidney care, including dialysis. Many questions include a lab value to interpret. Below are 5 free sample questions for the OMSB nursing exam, each with the answer and a rationale.
What this topic covers
- Fluid balance, dehydration and overload
- Potassium, sodium, calcium and magnesium imbalances
- Acid-base interpretation
- Acute kidney injury and chronic kidney disease
- Haemodialysis fistula care and peritoneal dialysis
- Catheter care and UTI prevention
The full bank has 100 renal, fluids & electrolytes questions, part of 1,500 questions across 16 nursing topics.
Free OMSB renal, fluids & electrolytes questions
1. Which medication group should the nurse question for a patient with acute kidney injury because it may worsen kidney function?
- A. Non-steroidal anti-inflammatory drugs such as ibuprofen
- B. Proton pump inhibitors
- C. Paracetamol at normal doses
- D. Oral vitamin D
Show answer and rationale
NSAIDs reduce renal blood flow and are nephrotoxic, particularly in AKI, dehydration and older adults. Aminoglycosides and contrast media are other common nephrotoxins.
Reference: Standard nursing pharmacology – NSAIDs
2. A nurse is teaching a patient with chronic kidney disease (not on dialysis) about diet. Which advice is appropriate?
- A. Increase intake of bananas, oranges and potatoes
- B. Use salt substitutes containing potassium chloride
- C. Eat unlimited processed cheese and cola drinks
- D. Limit sodium, potassium and phosphate as advised by the dietitian
Show answer and rationale
CKD diets typically restrict sodium, potassium and phosphate, with controlled protein. Salt substitutes are usually potassium chloride and can cause hyperkalaemia.
Reference: Lewis Medical-Surgical Nursing – chronic kidney disease nutrition
3. Which ECG finding is associated with hypokalaemia?
- A. Tall, peaked T waves
- B. Widened QRS complex with absent P waves
- C. Prominent U waves and flattened T waves
- D. Sine-wave pattern
Show answer and rationale
Hypokalaemia produces flattened or inverted T waves, ST depression and prominent U waves. Peaked T waves, wide QRS and sine waves are features of hyperkalaemia.
Reference: Lewis Medical-Surgical Nursing – hypokalaemia
4. A patient has a pH of 7.30, PaCO2 3.9 kPa (29 mmHg) and HCO3− 15 mmol/L. How is this best interpreted?
- A. Metabolic acidosis with partial respiratory compensation
- B. Respiratory acidosis with metabolic compensation
- C. Fully compensated respiratory alkalosis
- D. Mixed respiratory and metabolic alkalosis
Show answer and rationale
Low pH and low bicarbonate indicate metabolic acidosis; the low PaCO2 shows the lungs are compensating, but the pH is still abnormal, so compensation is partial.
Reference: Lewis Medical-Surgical Nursing – acid–base interpretation
5. A patient is receiving intravenous magnesium sulfate. Which finding requires the nurse to stop the infusion and report immediately?
- A. Respiratory rate 16/min
- B. Absent deep tendon reflexes and respiratory rate 9/min
- C. Mild warmth and flushing at the start of the infusion
- D. Urine output 60 mL/hour
Show answer and rationale
Loss of deep tendon reflexes and respiratory depression indicate magnesium toxicity. Calcium gluconate is the antidote.
Reference: Standard nursing pharmacology – magnesium sulfate
Study tip
Memorise the normal potassium range and the ECG changes of high potassium. It is one of the most common exam questions.
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