Introduction
Fluid and electrolyte balance represents a cornerstone of nursing practice and is extensively tested on the NCLEX-PN examination, as disturbances in this delicate equilibrium can rapidly lead to life-threatening complications across all patient populations. Licensed Practical Nurses must demonstrate comprehensive understanding of the physiological mechanisms that regulate fluid distribution between intracellular and extracellular compartments, including the roles of osmosis, diffusion, and active transport in maintaining homeostasis. Electrolyte imbalances such as hyponatremia, hyperkalemia, hypocalcemia, and hypomagnesemia present with distinct clinical manifestations that nurses must recognize promptly to facilitate appropriate interventions and prevent cardiac arrhythmias, seizures, or respiratory failure. Intravenous therapy management requires nurses to understand the differences between isotonic, hypotonic, and hypertonic solutions, as well as their specific indications and potential complications including fluid overload and infiltration. Acid-base disorders, including respiratory and metabolic acidosis and alkalosis, demand that nurses interpret arterial blood gas values accurately and understand compensatory mechanisms the body employs to restore pH balance. The NCLEX-PN tests candidates on their ability to calculate fluid intake and output precisely, recognize signs of dehydration and fluid volume excess, and implement appropriate nursing interventions for various fluid and electrolyte disturbances. Understanding the relationship between fluid balance and vital organ function, particularly cardiac and renal systems, is essential for providing safe patient care in medical-surgical, critical care, and long-term care settings. Nurses must also comprehend how certain medications, including diuretics, corticosteroids, and IV solutions, affect electrolyte levels and require careful monitoring. Knowledge of special populations at higher risk for fluid and electrolyte imbalances, such as elderly patients, infants, and those with chronic kidney disease, enables nurses to implement preventive strategies and early interventions. This topic area integrates pathophysiology, pharmacology, and clinical assessment skills, making it one of the most challenging yet essential components of the NCLEX-PN examination. These practice questions will test your ability to apply fluid and electrolyte concepts to realistic clinical scenarios and strengthen your readiness for licensure.
Practice Questions
Question 1: A patient with heart failure is receiving furosemide (Lasix) 40 mg IV twice daily. Which electrolyte imbalance should the nurse monitor for most closely?
A) Hyperkalemia
B) Hypokalemia
C) Hypernatremia
D) Hypercalcemia
Correct Answer: B) Hypokalemia
Explanation: Furosemide is a loop diuretic that causes potassium loss through the kidneys, putting patients at significant risk for hypokalemia. Low potassium levels can lead to dangerous cardiac arrhythmias, muscle weakness, and decreased bowel motility. Nurses must monitor serum potassium levels and assess for signs of hypokalemia including muscle cramps, weakness, irregular heartbeat, and fatigue. Loop diuretics typically cause hypokalemia rather than hyperkalemia, and while they affect sodium levels, hypokalemia is the most critical concern requiring close monitoring.
Question 2: A patient’s laboratory results show: Sodium 128 mEq/L (normal 135-145), Potassium 3.8 mEq/L (normal 3.5-5.0). Which assessment finding would the nurse expect?
A) Muscle twitching and hyperreflexia
B) Confusion and headache
C) Increased deep tendon reflexes
D) Bradycardia
Correct Answer: B) Confusion and headache
Explanation: The patient has hyponatremia (low sodium level of 128 mEq/L). Low sodium levels cause cerebral edema and neurological symptoms including confusion, headache, lethargy, seizures, and in severe cases, coma. Sodium is crucial for nerve impulse transmission and cellular function. Muscle twitching and hyperreflexia are associated with hypocalcemia or hypomagnesemia, not hyponatremia. Hyponatremia typically does not cause increased reflexes or bradycardia as primary symptoms.
Question 3: A nurse is caring for a patient receiving 0.9% Normal Saline IV. This solution is classified as:
A) Hypotonic
B) Isotonic
C) Hypertonic
D) Colloid
Correct Answer: B) Isotonic
Explanation: 0.9% Normal Saline (NS) is an isotonic solution, meaning it has the same osmolality as blood plasma and does not cause fluid shifts between intracellular and extracellular compartments. Isotonic solutions are used for fluid volume replacement without altering cellular fluid balance. Hypotonic solutions (like 0.45% NS) cause fluid to move into cells, hypertonic solutions (like 3% NS) draw fluid out of cells, and colloids contain large protein molecules. Understanding solution types is essential for safe IV therapy administration.
Question 4: A patient with chronic kidney disease has a potassium level of 6.2 mEq/L (normal 3.5-5.0). Which ECG change would the nurse expect to observe?
A) Prolonged QT interval
B) Peaked T waves
C) Depressed ST segment
D) Widened QRS complex with flattened T waves
Correct Answer: B) Peaked T waves
Explanation: Hyperkalemia (elevated potassium) initially causes peaked, tall T waves on the ECG, which is often the earliest cardiac manifestation. As potassium levels continue to rise, more dangerous changes occur including widened QRS complexes, prolonged PR intervals, and eventually cardiac arrest. Prolonged QT intervals are associated with hypocalcemia and certain medications. Depressed ST segments can indicate ischemia. Widened QRS with flattened T waves is seen in hypokalemia, not hyperkalemia. Recognizing ECG changes in electrolyte imbalances is critical for preventing life-threatening arrhythmias.
Question 5: A patient is admitted with severe vomiting for 3 days. Which acid-base imbalance is the patient most likely experiencing?
A) Respiratory acidosis
B) Respiratory alkalosis
C) Metabolic acidosis
D) Metabolic alkalosis
Correct Answer: D) Metabolic alkalosis
Explanation: Prolonged vomiting causes loss of hydrochloric acid (HCl) from the stomach, leading to metabolic alkalosis (elevated blood pH due to loss of acid or excess base). The body loses hydrogen ions and chloride, while retaining bicarbonate, resulting in an alkaline state. Respiratory acidosis results from hypoventilation and CO2 retention. Respiratory alkalosis results from hyperventilation. Metabolic acidosis results from conditions like diabetic ketoacidosis or diarrhea. Understanding the causes of acid-base imbalances helps nurses anticipate complications and implement appropriate interventions.
Question 6: A nurse is calculating a patient’s intake and output for an 8-hour shift. The patient received: 1000 mL IV fluid, 8 oz juice, 6 oz coffee, 4 oz gelatin. Output: 800 mL urine, 200 mL emesis. What is the patient’s fluid balance? (Note: 1 oz = 30 mL)
A) +540 mL
B) +1540 mL
C) +740 mL
D) +1000 mL
Correct Answer: A) +540 mL
Explanation: Total intake: 1000 mL (IV) + 240 mL (8 oz juice) + 180 mL (6 oz coffee) + 120 mL (4 oz gelatin) = 1540 mL. Total output: 800 mL (urine) + 200 mL (emesis) = 1000 mL. Fluid balance: 1540 mL – 1000 mL = +540 mL. A positive balance indicates the patient retained more fluid than was eliminated. Accurate intake and output calculation is essential for monitoring fluid status, especially in patients with cardiac or renal conditions.
Question 7: A patient receiving IV therapy develops swelling, coolness, and pallor at the IV site. What complication should the nurse suspect?
A) Phlebitis
B) Infiltration
C) Air embolism
D) Fluid overload
Correct Answer: B) Infiltration
Explanation: Infiltration occurs when IV fluid leaks into surrounding tissue rather than entering the vein, causing swelling, coolness, pallor, and discomfort at the site. The nurse should stop the IV immediately, remove the catheter, elevate the affected extremity, and apply warm or cold compresses as appropriate. Phlebitis presents with warmth, redness, and a palpable cord along the vein. Air embolism causes sudden respiratory distress and cardiovascular collapse. Fluid overload presents with systemic symptoms like dyspnea, crackles, and jugular vein distention, not localized site changes.
Question 8: A patient with diabetes insipidus has a urine specific gravity of 1.002 (normal 1.010-1.030). What does this finding indicate?
A) Concentrated urine
B) Dilute urine
C) Normal urine concentration
D) Presence of glucose in urine
Correct Answer: B) Dilute urine
Explanation: A specific gravity of 1.002 is very low, indicating dilute urine with minimal solutes. Diabetes insipidus is caused by deficient antidiuretic hormone (ADH), resulting in the kidneys’ inability to concentrate urine, leading to excessive dilute urine output and risk of dehydration. Normal specific gravity ranges from 1.010-1.030. Values below 1.010 indicate dilute urine, while values above 1.030 indicate concentrated urine. This finding is consistent with diabetes insipidus and requires monitoring for dehydration and electrolyte imbalances.
Question 9: A patient receiving a blood transfusion develops dyspnea, crackles in lung bases, and jugular vein distention. What is the priority nursing action?
A) Continue the transfusion and monitor vital signs
B) Slow the transfusion rate and notify the physician
C) Stop the transfusion immediately and place patient upright
D) Administer oxygen and continue transfusion at slower rate
Correct Answer: C) Stop the transfusion immediately and place patient upright
Explanation: These symptoms indicate circulatory overload (fluid volume excess), a transfusion complication requiring immediate intervention. The nurse must stop the transfusion immediately to prevent further fluid administration, position the patient upright to facilitate breathing and reduce venous return, administer oxygen, and notify the physician. Continuing the transfusion in any form would worsen the condition. Circulatory overload occurs when blood products are administered too rapidly or to patients with compromised cardiac or renal function. This is a medical emergency requiring prompt recognition and intervention.
Question 10: A patient’s arterial blood gas results show: pH 7.30 (normal 7.35-7.45), PaCO2 50 mmHg (normal 35-45), HCO3 24 mEq/L (normal 22-26). What acid-base imbalance is present?
A) Respiratory acidosis
B) Respiratory alkalosis
C) Metabolic acidosis
D) Metabolic alkalosis
Correct Answer: A) Respiratory acidosis
Explanation: The pH is low (acidotic), and the PaCO2 is elevated, indicating respiratory acidosis. The bicarbonate (HCO3) is normal, showing no metabolic compensation has occurred yet. Respiratory acidosis results from hypoventilation and CO2 retention, commonly seen in conditions like COPD, pneumonia, or respiratory depression from opioids. The elevated CO2 combines with water to form carbonic acid, lowering blood pH. Respiratory alkalosis would show low PaCO2, while metabolic disorders would show abnormal HCO3 levels as the primary problem.
Question 11: A patient with hypocalcemia is at risk for which complication?
A) Kidney stones
B) Tetany and seizures
C) Bone demineralization
D) Cardiac dysrhythmias with shortened QT interval
Correct Answer: B) Tetany and seizures
Explanation: Hypocalcemia (low calcium) causes increased neuromuscular excitability, leading to tetany (involuntary muscle spasms), positive Chvostek’s and Trousseau’s signs, paresthesias, and potentially life-threatening seizures or laryngospasm. Calcium is essential for proper nerve and muscle function. Kidney stones are associated with hypercalcemia, not hypocalcemia. While hypocalcemia can cause cardiac dysrhythmias, it causes prolonged QT intervals, not shortened ones. Bone demineralization occurs with chronic hypocalcemia but is not the most immediate life-threatening complication.
Question 12: A nurse is preparing to administer a hypertonic saline solution (3% NaCl). Which patient condition would this solution be most appropriate for?
A) Dehydration from diarrhea
B) Severe hyponatremia with neurological symptoms
C) Fluid volume deficit from hemorrhage
D) Routine maintenance fluid therapy
Correct Answer: B) Severe hyponatremia with neurological symptoms
Explanation: Hypertonic saline (3% NaCl) is used to treat severe, symptomatic hyponatremia, particularly when patients exhibit neurological symptoms like seizures or altered mental status. The hypertonic solution draws fluid from cells into the vascular space and rapidly increases serum sodium levels. This solution must be administered slowly via infusion pump with frequent monitoring, as rapid correction can cause osmotic demyelination syndrome. Isotonic solutions are preferred for dehydration, hemorrhage, and routine maintenance. Hypertonic solutions are reserved for specific critical situations due to their risks.
Question 13: A patient taking digoxin has a potassium level of 3.0 mEq/L (normal 3.5-5.0). Why is this finding particularly concerning?
A) Hypokalemia increases risk of digoxin toxicity
B) Hypokalemia decreases digoxin effectiveness
C) Hypokalemia causes digoxin to be excreted too rapidly
D) Hypokalemia has no effect on digoxin therapy
Correct Answer: A) Hypokalemia increases risk of digoxin toxicity
Explanation: Hypokalemia significantly increases the risk of digoxin toxicity because low potassium levels enhance digoxin’s binding to cardiac tissue, potentiating its effects and increasing the likelihood of dangerous arrhythmias. Patients on digoxin must maintain normal potassium levels, and those receiving diuretics (which can cause potassium loss) require careful monitoring. Signs of digoxin toxicity include nausea, vomiting, visual disturbances (yellow-green halos), and cardiac arrhythmias. The nurse should notify the physician before administering digoxin when potassium levels are low.
Question 14: A patient is receiving D5W (5% Dextrose in Water) intravenously. Once the dextrose is metabolized, this solution becomes:
A) Isotonic
B) Hypertonic
C) Hypotonic
D) Remains unchanged
Correct Answer: C) Hypotonic
Explanation: D5W is initially isotonic when in the bag, but once infused and the dextrose is metabolized by the body, it becomes hypotonic (essentially free water). This causes fluid to shift from the vascular space into cells, making it useful for treating cellular dehydration but potentially dangerous in patients at risk for cerebral edema or increased intracranial pressure. Understanding how solutions behave in the body is essential for selecting appropriate IV fluids and preventing complications. D5W should not be used for fluid resuscitation or in patients with head injuries.
Question 15: A patient with chronic diarrhea is at highest risk for which electrolyte imbalance?
A) Hyperkalemia and hypernatremia
B) Hypokalemia and metabolic acidosis
C) Hypercalcemia and respiratory alkalosis
D) Hypermagnesemia and metabolic alkalosis
Correct Answer: B) Hypokalemia and metabolic acidosis
Explanation: Diarrhea causes significant loss of potassium and bicarbonate through the gastrointestinal tract, leading to hypokalemia and metabolic acidosis. The large intestine normally absorbs potassium, and excessive diarrhea prevents this absorption while also causing direct potassium loss. Loss of bicarbonate (a base) results in metabolic acidosis. Patients with chronic diarrhea require careful monitoring of electrolytes and acid-base balance, with replacement therapy as needed. Diarrhea causes fluid and electrolyte losses, not excesses, so hyperkalemia and hypernatremia would not be expected.
Summary
These 15 practice questions comprehensively cover fluid and electrolyte balance concepts essential for NCLEX-PN success, including IV therapy management, electrolyte imbalances and their clinical manifestations, acid-base disorders, intake and output calculations, transfusion complications, and the relationship between medications and electrolyte levels. Mastering these concepts is fundamental to safe nursing practice across all clinical settings.