FCCS FCCS Fluid and Electrolyte Management 2 — Questions and Answers
Question 1: A patient with hyperkalemia (K+ = 6.8 mEq/L) shows peaked T-waves and widened QRS on ECG. What is the FIRST intervention?
- Sodium polystyrene sulfonate (Kayexalate)
- Furosemide IV
- Calcium gluconate IV (Correct answer)
- Insulin and dextrose
Correct answer: Calcium gluconate IV
Calcium gluconate stabilizes the cardiac membrane and counteracts the cardiotoxic effects of hyperkalemia; it should be given first when ECG changes are present.
Question 2: A critically ill patient develops carpopedal spasm and a positive Chvostek's sign. Which electrolyte abnormality is most likely?
- Hyponatremia
- Hyperkalemia
- Hypocalcemia (Correct answer)
- Hypophosphatemia
Correct answer: Hypocalcemia
Hypocalcemia causes neuromuscular excitability, manifesting as carpopedal spasm, Chvostek's sign (facial nerve tapping), and Trousseau's sign.
Question 3: Which electrolyte deficiency must be corrected before refractory hypokalemia can be successfully treated?
- Sodium
- Calcium
- Magnesium (Correct answer)
- Phosphate
Correct answer: Magnesium
Hypomagnesemia impairs renal potassium conservation and cellular potassium uptake, making hypokalemia refractory to replacement until magnesium is corrected.
Question 4: What is the maximum recommended rate of sodium correction in chronic hyponatremia to prevent osmotic demyelination syndrome?
- 1–2 mEq/L per hour
- 8–10 mEq/L per 24 hours (Correct answer)
- 15–20 mEq/L per 24 hours
- 25 mEq/L per 24 hours
Correct answer: 8–10 mEq/L per 24 hours
Correcting chronic hyponatremia faster than 8–10 mEq/L per 24 hours risks osmotic demyelination (central pontine myelinolysis), a devastating neurological complication.
Question 5: In diabetic ketoacidosis (DKA), why may serum potassium appear normal or elevated despite total body potassium depletion?
- Insulin resistance causes potassium retention in cells
- Acidosis shifts potassium from intracellular to extracellular fluid (Correct answer)
- Hyperglycemia increases gastrointestinal potassium absorption
- Osmotic diuresis selectively preserves potassium
Correct answer: Acidosis shifts potassium from intracellular to extracellular fluid
Metabolic acidosis drives hydrogen ions into cells in exchange for potassium moving out, falsely elevating serum potassium despite total body depletion.
Question 6: Which ECG change is most characteristic of hypokalemia?
- Peaked T-waves
- Prolonged PR interval
- U-waves and flattened T-waves (Correct answer)
- Wide QRS complex
Correct answer: U-waves and flattened T-waves
Hypokalemia classically produces U-waves (positive deflection after T-wave), T-wave flattening, and in severe cases ST depression and prolonged QU interval.
Question 7: What is the most common cause of hyperphosphatemia in critically ill patients?
- Excessive dietary phosphate intake
- Malnutrition and refeeding syndrome
- Renal failure (Correct answer)
- Hyperparathyroidism
Correct answer: Renal failure
Renal failure reduces phosphate excretion, making it the most common cause of hyperphosphatemia in critically ill patients.
FCCS FCCS Fluid and Electrolyte Management 2
A patient with hyperkalemia (K+ = 6.8 mEq/L) shows peaked T-waves and widened QRS on ECG.
What is the FIRST intervention?