FCCS FCCS Fluid and Electrolyte Management — Questions and Answers
Question 1: Which electrolyte is the primary determinant of extracellular fluid volume and intravascular volume?
- Potassium
- Sodium (Correct answer)
- Chloride
- Bicarbonate
Correct answer: Sodium
Sodium is the principal extracellular cation and the primary osmole that determines extracellular fluid volume.
Question 2: Which IV fluid is considered isotonic and is appropriate for initial fluid resuscitation in hypovolemia?
- 5% Dextrose in water (D5W)
- 0.45% Normal saline
- 0.9% Normal saline (Correct answer)
- 3% Hypertonic saline
Correct answer: 0.9% Normal saline
0.9% normal saline is isotonic (308 mOsm/L) and remains in the extracellular space, making it appropriate for volume resuscitation.
Question 3: What is the normal serum sodium concentration range?
- 120–130 mEq/L
- 125–135 mEq/L
- 135–145 mEq/L (Correct answer)
- 145–155 mEq/L
Correct answer: 135–145 mEq/L
Normal serum sodium ranges from 135 to 145 mEq/L; values outside this range indicate hypo- or hypernatremia.
Question 4: Which urine output threshold is commonly used to indicate adequate fluid resuscitation in critically ill adults?
- 0.1 mL/kg/hr
- 0.3 mL/kg/hr
- 0.5 mL/kg/hr (Correct answer)
- 1.5 mL/kg/hr
Correct answer: 0.5 mL/kg/hr
A urine output of at least 0.5 mL/kg/hr reflects adequate renal perfusion and is a standard resuscitation endpoint.
Question 5: What is the most common cause of hyponatremia in ICU patients?
- Diabetes insipidus
- Excessive sodium intake
- Syndrome of Inappropriate Antidiuretic Hormone (SIADH) (Correct answer)
- Hyperglycemia
Correct answer: Syndrome of Inappropriate Antidiuretic Hormone (SIADH)
SIADH causes inappropriate free water retention, diluting serum sodium and is the most frequent cause of hyponatremia in hospitalized ICU patients.
Question 6: Which IV fluid is considered a balanced crystalloid and is preferred over normal saline to reduce hyperchloremic acidosis?
- D5W
- Lactated Ringer's solution (Correct answer)
- 0.45% NaCl
- 3% NaCl
Correct answer: Lactated Ringer's solution
Lactated Ringer's solution has a composition closer to plasma and contains less chloride, reducing the risk of hyperchloremic metabolic acidosis.
Question 7: A patient with hemorrhagic shock has a blood pressure of 80/50 mmHg and heart rate of 130 bpm. What is the most appropriate initial fluid strategy?
- Administer 250 mL D5W bolus
- Restrict all fluids until bleeding is controlled
- Administer 1–2 L balanced crystalloid bolus (Correct answer)
- Give 50 mEq sodium bicarbonate IV
Correct answer: Administer 1–2 L balanced crystalloid bolus
Initial resuscitation in hemorrhagic shock uses 1–2 L of balanced crystalloid (Lactated Ringer's or normal saline) while preparing for blood product administration.
Question 8: 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 9: 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 10: 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 11: 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 12: 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 13: 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 14: 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.
