MSNCB Fluid & Electrolyte Balance 2 — Questions and Answers
Question 1: A patient's ABG shows pH 7.28, PaCO2 38 mmHg, HCO3 16 mEq/L. Which acid-base disturbance does this indicate?
- Respiratory acidosis
- Metabolic alkalosis
- Metabolic acidosis (Correct answer)
- Respiratory alkalosis
Correct answer: Metabolic acidosis
A pH below 7.35 with low bicarbonate (<22 mEq/L) and normal PaCO2 indicates uncompensated metabolic acidosis.
Question 2: Which clinical finding is most associated with hypocalcemia?
- Constipation
- Bradycardia
- Trousseau's sign (Correct answer)
- Polyuria
Correct answer: Trousseau's sign
Trousseau's sign — carpopedal spasm triggered by BP cuff inflation — is a classic manifestation of hypocalcemia due to increased neuromuscular excitability.
Question 3: A patient receiving prolonged total parenteral nutrition (TPN) is at risk for which electrolyte imbalance that can cause respiratory muscle weakness?
- Hypermagnesemia
- Hypophosphatemia (Correct answer)
- Hyperkalemia
- Hypernatremia
Correct answer: Hypophosphatemia
Refeeding syndrome with aggressive TPN can cause hypophosphatemia, which impairs ATP production and can result in severe respiratory muscle weakness or failure.
Question 4: Which symptom is characteristic of hypermagnesemia?
- Muscle cramps and tetany
- Hypertension and tachycardia
- Loss of deep tendon reflexes (Correct answer)
- Positive Chvostek's sign
Correct answer: Loss of deep tendon reflexes
Hypermagnesemia suppresses neuromuscular transmission, and loss of deep tendon reflexes is an early, clinically significant sign of magnesium toxicity.
Question 5: A patient has a serum potassium of 6.2 mEq/L. Which ECG change would the nurse most likely observe?
- Flattened T waves
- Peaked (tall, narrow) T waves (Correct answer)
- Prominent U waves
- Shortened QT interval only
Correct answer: Peaked (tall, narrow) T waves
Hyperkalemia classically produces tall, peaked, narrow T waves on ECG, representing one of the earliest electrocardiographic signs of elevated potassium.
Question 6: Which set of findings is most consistent with SIADH (Syndrome of Inappropriate Antidiuretic Hormone)?
- Hypernatremia with polyuria
- Hyponatremia with concentrated urine (Correct answer)
- Hypernatremia with decreased urine output
- Hyponatremia with dilute urine
Correct answer: Hyponatremia with concentrated urine
SIADH causes excessive ADH secretion, leading to water retention, dilutional hyponatremia, and paradoxically concentrated urine (elevated urine osmolality).
Question 7: A nurse is preparing to administer potassium chloride IV to a patient with hypokalemia. Which action is essential for patient safety?
- Administer as an IV bolus for rapid correction
- Dilute and infuse at no more than 10–20 mEq/hour via infusion pump (Correct answer)
- Mix only with D5W to prevent vascular irritation
- Administer undiluted through a central line
Correct answer: Dilute and infuse at no more than 10–20 mEq/hour via infusion pump
IV potassium must always be diluted and administered slowly (≤10–20 mEq/hr) via a controlled infusion pump to prevent fatal cardiac arrhythmias from rapid potassium shifts.
MSNCB Fluid & Electrolyte Balance 2
A patient's ABG shows pH 7.28, PaCO2 38 mmHg, HCO3 16 mEq/L.
Which acid-base disturbance does this indicate?