NACE Fluid and Electrolyte Balance 2 — Questions and Answers
Question 1: A nurse taps a patient's facial nerve anterior to the ear and observes facial muscle twitching. This positive Chvostek's sign indicates which electrolyte imbalance?
- Hyperkalemia
- Hypomagnesemia
- Hypocalcemia (Correct answer)
- Hyponatremia
Correct answer: Hypocalcemia
A positive Chvostek's sign (facial muscle twitching upon tapping the facial nerve) indicates hypocalcemia, which increases neuromuscular excitability by reducing calcium's stabilizing effect on nerve membranes.
Question 2: A patient receiving total parenteral nutrition (TPN) develops tetany and muscle spasms. Which laboratory finding would confirm hypomagnesemia?
- Serum magnesium 0.8 mEq/L (Correct answer)
- Serum magnesium 1.8 mEq/L
- Serum magnesium 2.5 mEq/L
- Serum magnesium 3.0 mEq/L
Correct answer: Serum magnesium 0.8 mEq/L
The normal serum magnesium level is 1.5–2.5 mEq/L; a level of 0.8 mEq/L confirms hypomagnesemia, which causes neuromuscular irritability and tetany similar to hypocalcemia.
Question 3: A patient's ABG results show: pH 7.30, PaCO2 38 mmHg, HCO3- 18 mEq/L. How should the nurse interpret these results?
- Respiratory acidosis with compensation
- Respiratory alkalosis
- Metabolic acidosis (Correct answer)
- Metabolic alkalosis
Correct answer: Metabolic acidosis
A pH of 7.30 (acidosis), normal PaCO2 (38 mmHg), and low HCO3- (18 mEq/L) indicate metabolic acidosis as the primary disorder, with the respiratory system not yet compensating.
Question 4: A nurse is administering a hypotonic IV solution. Which physiologic effect should be anticipated?
- Fluid shifts from cells into the vascular space
- Fluid shifts from the vascular space into cells (Correct answer)
- No change in cellular fluid volume
- Increased serum osmolality
Correct answer: Fluid shifts from the vascular space into cells
Hypotonic solutions have lower osmolality than plasma, causing water to move by osmosis from the vascular space into cells, expanding intracellular volume and potentially causing cellular swelling.
Question 5: Which clinical presentation is most consistent with third-spacing of fluid?
- Increased urine output with elevated blood pressure
- Decreased urine output with low intravascular volume despite visible fluid accumulation (Correct answer)
- Peripheral edema with hypertension and bounding pulse
- Jugular vein distension with crackles and weight gain
Correct answer: Decreased urine output with low intravascular volume despite visible fluid accumulation
Third-spacing occurs when fluid shifts into non-functional compartments (e.g., ascites, burn edema), reducing intravascular volume and urine output while fluid appears to accumulate in the body.
Question 6: A postoperative patient develops respiratory acidosis. Which compensatory change would the nurse expect to see in the metabolic component?
- Decreased serum bicarbonate (HCO3-)
- Increased serum bicarbonate (HCO3-) (Correct answer)
- Decreased pH below 7.20
- Decreased PaCO2 below 35 mmHg
Correct answer: Increased serum bicarbonate (HCO3-)
In respiratory acidosis, the kidneys compensate by retaining bicarbonate (HCO3-) to buffer excess carbonic acid and gradually restore the blood pH toward normal.
Question 7: A patient develops hypophosphatemia after several days NPO without phosphate supplementation. Which complication is the nurse most concerned about?
- Renal calculi formation
- Muscle weakness and respiratory failure (Correct answer)
- Peaked T waves and cardiac arrhythmias
- Pathological bone fractures from calcification
Correct answer: Muscle weakness and respiratory failure
Hypophosphatemia impairs ATP production, leading to profound muscle weakness that can affect the diaphragm and intercostal muscles, causing life-threatening respiratory failure.
NACE Fluid and Electrolyte Balance 2
A nurse taps a patient's facial nerve anterior to the ear and observes facial muscle twitching.
This positive Chvostek's sign indicates which electrolyte imbalance?