FCCS Fluid and Electrolyte Management Flashcards

Which electrolyte is the primary determinant of extracellular fluid volume and intravascular volume?

Answer: Sodium

Sodium is the principal extracellular cation and the primary osmole that determines extracellular fluid volume.

Which IV fluid is considered isotonic and is appropriate for initial fluid resuscitation in hypovolemia?

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.

What is the normal serum sodium concentration range?

Answer: 135–145 mEq/L

Normal serum sodium ranges from 135 to 145 mEq/L; values outside this range indicate hypo- or hypernatremia.

Which urine output threshold is commonly used to indicate adequate fluid resuscitation in critically ill adults?

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.

What is the most common cause of hyponatremia in ICU patients?

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.

Which IV fluid is considered a balanced crystalloid and is preferred over normal saline to reduce hyperchloremic acidosis?

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.

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?

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.

A patient with hyperkalemia (K+ = 6.8 mEq/L) shows peaked T-waves and widened QRS on ECG. What is the FIRST intervention?

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.

A critically ill patient develops carpopedal spasm and a positive Chvostek's sign. Which electrolyte abnormality is most likely?

Answer: Hypocalcemia

Hypocalcemia causes neuromuscular excitability, manifesting as carpopedal spasm, Chvostek's sign (facial nerve tapping), and Trousseau's sign.

Which electrolyte deficiency must be corrected before refractory hypokalemia can be successfully treated?

Answer: Magnesium

Hypomagnesemia impairs renal potassium conservation and cellular potassium uptake, making hypokalemia refractory to replacement until magnesium is corrected.

What is the maximum recommended rate of sodium correction in chronic hyponatremia to prevent osmotic demyelination syndrome?

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.

In diabetic ketoacidosis (DKA), why may serum potassium appear normal or elevated despite total body potassium depletion?

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.

Which ECG change is most characteristic of hypokalemia?

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.

What is the most common cause of hyperphosphatemia in critically ill patients?

Answer: Renal failure

Renal failure reduces phosphate excretion, making it the most common cause of hyperphosphatemia in critically ill patients.