NURS 301: Lewis Medical-Surgical Nursing 12th Edition Exam
Prep with Detailed Rationales
Course Code: NURS 301
Course Name: Medical-Surgical Nursing
Topic: Comprehensive Core Concepts and Clinical Pathophysiology Exam Prep
Academic Year: 2026/2027
,Part I: Fluid, Electrolyte, and Acid-Base Imbalances
Question 1
A nurse is assessing a patient admitted with severe, protracted vomiting. The
patient’s arterial blood gas (ABG) results reveal a pH of 7.50, PaCO2 of 48
mmHg, and HCO3 of 36 mEq/L. Based on these clinical data, which acid-base
imbalance is the patient experiencing?
A. Respiratory acidosis
B. Respiratory alkalosis
C. Metabolic acidosis
D. Metabolic alkalosis
CORRECT ANSWER: D. Metabolic alkalosis
RATIONALE: The patient’s pH is 7.50, which is greater than the normal range
of 7.35–7.45, confirming an alkalotic state. The HCO3 is 36 mEq/L, which is
elevated above the normal range of 22–26 mEq/L, indicating a metabolic origin for
the alkalosis. This occurs because severe vomiting causes a massive loss of
hydrochloric acid (HCl) from the stomach, leaving an excess of bicarbonate ions in
the extracellular fluid. The PaCO2 is 48 mmHg, which is elevated above the
normal 35–45 mmHg range; this represents partial respiratory compensation, as the
lungs hypoventilate to retain carbon dioxide (an acid) to bring the pH back toward
normal. Options A and B are incorrect because the primary driver is metabolic
(bicarbonate), not respiratory. Option C is incorrect because the pH indicates
alkalosis, not acidosis.
Question 2
A patient with chronic kidney disease (CKD) presents with a serum potassium
level of 6.8 mEq/L. Which cardiac manifestation should the nurse immediately
assess for on the electrocardiogram (ECG)?
A. U waves
B. ST-segment depression
C. Tall, peaked T waves
D. Prolonged QT interval
CORRECT ANSWER: C. Tall, peaked T waves
RATIONALE: A serum potassium level of 6.8 mEq/L signifies severe
hyperkalemia (normal range: 3.5–5.0 mEq/L). Potassium is the primary
,intracellular cation, and its concentration gradient across the myocardial cell
membrane dictates the resting membrane potential. Elevated extracellular
potassium impairs myocardial repolarization, manifesting classically on an ECG as
tall, peaked T waves, along with a prolonged PR interval, widening of the QRS
complex, and eventual loss of P waves or progression to ventricular fibrillation.
Option A (U waves) and Option B (ST depression) are classic signs of
hypokalemia, not hyperkalemia. Option D (prolonged QT interval) is associated
with hypocalcemia.
Question 3
The nurse is caring for a patient who has been receiving aggressive loop diuretic
therapy for heart failure. The patient reports muscle weakness and cramping in the
lower extremities. Which electrolyte imbalance does the nurse suspect?
A. Hyperkalemia
B. Hypernatremia
C. Hypokalemia
D. Hypocalcemia
CORRECT ANSWER: C. Hypokalemia
RATIONALE: Loop diuretics (such as furosemide) inhibit the Na-K-2Cl
cotransporter in the thick ascending limb of the loop of Henle, leading to a
profound excretion of sodium, chloride, water, and potassium in the urine.
Hypokalemia impairs the resting membrane potential of skeletal and smooth
muscle cells, reducing their contractility and excitability, which clinically
manifests as neuromuscular weakness, leg cramps, fatigue, and decreased deep
tendon reflexes. Options A, B, and D do not align directly with the classic,
isolated, high-volume potassium wasting seen with loop diuretic abuse or intensive
therapy without adequate supplementation.
Question 4
A patient with a history of alcohol use disorder presents with tremors, hyperactive
deep tendon reflexes, and a positive Chvostek's sign. The nurse anticipates that
these neuromuscular symptoms are driven by which underlying electrolyte deficit?
A. Hypokalemia
B. Hypomagnesemia
C. Hypercalcemia
D. Hyponatremia
, CORRECT ANSWER: B. Hypomagnesemia
RATIONALE: Chronic alcohol ingestion leads to significant hypomagnesemia
due to poor dietary intake, decreased intestinal absorption, and alcohol-induced
renal tubular wasting of magnesium. Magnesium acts as an intracellular stabilizer;
a deficit increases neuromuscular excitability by facilitating acetylcholine release
at the neuromuscular junction. This mimics hypocalcemia, causing hyperreflexia,
tremors, seizures, and classic signs like Chvostek's sign (facial muscle twitching
when the facial nerve is tapped). Option A is incorrect as hypokalemia presents
with muscle weakness and hypoactivity. Option C reduces neuromuscular
excitability. Option D primarily causes central nervous system changes (confusion,
seizures) due to cellular swelling rather than isolated peripheral hyperreflexia.
Question 5
The nurse is reviewing the laboratory results of a patient with small cell lung
cancer who has developed Syndrome of Inappropriate Antidiuretic Hormone
(SIADH). Which lab finding requires immediate nursing intervention?
A. Serum sodium 142 mEq/L
B. Serum sodium 118 mEq/L
C. Serum osmolality 295 mOsm/kg
D. Urine specific gravity 1.005
CORRECT ANSWER: B. Serum sodium 118 mEq/L
RATIONALE: SIADH involves excessive release of antidiuretic hormone
(ADH) from either the posterior pituitary or an ectopic source (like small cell lung
cancer). This excess ADH causes the renal collecting ducts to reabsorb water
indiscriminately, expanding extracellular fluid volume and causing severe
dilutional hyponatremia. A serum sodium level of 118 mEq/L is critically low
(normal: 135–145 mEq/L) and puts the patient at extreme risk for cerebral edema,
increased intracranial pressure, seizures, coma, and death. Option A and C are
normal values. Option D reflects dilute urine, whereas SIADH causes highly
concentrated urine with a high specific gravity (typically >1.030).
Part II: Visual Assessment Tools in Electrolyte Pathophysiology
Question 6
Prep with Detailed Rationales
Course Code: NURS 301
Course Name: Medical-Surgical Nursing
Topic: Comprehensive Core Concepts and Clinical Pathophysiology Exam Prep
Academic Year: 2026/2027
,Part I: Fluid, Electrolyte, and Acid-Base Imbalances
Question 1
A nurse is assessing a patient admitted with severe, protracted vomiting. The
patient’s arterial blood gas (ABG) results reveal a pH of 7.50, PaCO2 of 48
mmHg, and HCO3 of 36 mEq/L. Based on these clinical data, which acid-base
imbalance is the patient experiencing?
A. Respiratory acidosis
B. Respiratory alkalosis
C. Metabolic acidosis
D. Metabolic alkalosis
CORRECT ANSWER: D. Metabolic alkalosis
RATIONALE: The patient’s pH is 7.50, which is greater than the normal range
of 7.35–7.45, confirming an alkalotic state. The HCO3 is 36 mEq/L, which is
elevated above the normal range of 22–26 mEq/L, indicating a metabolic origin for
the alkalosis. This occurs because severe vomiting causes a massive loss of
hydrochloric acid (HCl) from the stomach, leaving an excess of bicarbonate ions in
the extracellular fluid. The PaCO2 is 48 mmHg, which is elevated above the
normal 35–45 mmHg range; this represents partial respiratory compensation, as the
lungs hypoventilate to retain carbon dioxide (an acid) to bring the pH back toward
normal. Options A and B are incorrect because the primary driver is metabolic
(bicarbonate), not respiratory. Option C is incorrect because the pH indicates
alkalosis, not acidosis.
Question 2
A patient with chronic kidney disease (CKD) presents with a serum potassium
level of 6.8 mEq/L. Which cardiac manifestation should the nurse immediately
assess for on the electrocardiogram (ECG)?
A. U waves
B. ST-segment depression
C. Tall, peaked T waves
D. Prolonged QT interval
CORRECT ANSWER: C. Tall, peaked T waves
RATIONALE: A serum potassium level of 6.8 mEq/L signifies severe
hyperkalemia (normal range: 3.5–5.0 mEq/L). Potassium is the primary
,intracellular cation, and its concentration gradient across the myocardial cell
membrane dictates the resting membrane potential. Elevated extracellular
potassium impairs myocardial repolarization, manifesting classically on an ECG as
tall, peaked T waves, along with a prolonged PR interval, widening of the QRS
complex, and eventual loss of P waves or progression to ventricular fibrillation.
Option A (U waves) and Option B (ST depression) are classic signs of
hypokalemia, not hyperkalemia. Option D (prolonged QT interval) is associated
with hypocalcemia.
Question 3
The nurse is caring for a patient who has been receiving aggressive loop diuretic
therapy for heart failure. The patient reports muscle weakness and cramping in the
lower extremities. Which electrolyte imbalance does the nurse suspect?
A. Hyperkalemia
B. Hypernatremia
C. Hypokalemia
D. Hypocalcemia
CORRECT ANSWER: C. Hypokalemia
RATIONALE: Loop diuretics (such as furosemide) inhibit the Na-K-2Cl
cotransporter in the thick ascending limb of the loop of Henle, leading to a
profound excretion of sodium, chloride, water, and potassium in the urine.
Hypokalemia impairs the resting membrane potential of skeletal and smooth
muscle cells, reducing their contractility and excitability, which clinically
manifests as neuromuscular weakness, leg cramps, fatigue, and decreased deep
tendon reflexes. Options A, B, and D do not align directly with the classic,
isolated, high-volume potassium wasting seen with loop diuretic abuse or intensive
therapy without adequate supplementation.
Question 4
A patient with a history of alcohol use disorder presents with tremors, hyperactive
deep tendon reflexes, and a positive Chvostek's sign. The nurse anticipates that
these neuromuscular symptoms are driven by which underlying electrolyte deficit?
A. Hypokalemia
B. Hypomagnesemia
C. Hypercalcemia
D. Hyponatremia
, CORRECT ANSWER: B. Hypomagnesemia
RATIONALE: Chronic alcohol ingestion leads to significant hypomagnesemia
due to poor dietary intake, decreased intestinal absorption, and alcohol-induced
renal tubular wasting of magnesium. Magnesium acts as an intracellular stabilizer;
a deficit increases neuromuscular excitability by facilitating acetylcholine release
at the neuromuscular junction. This mimics hypocalcemia, causing hyperreflexia,
tremors, seizures, and classic signs like Chvostek's sign (facial muscle twitching
when the facial nerve is tapped). Option A is incorrect as hypokalemia presents
with muscle weakness and hypoactivity. Option C reduces neuromuscular
excitability. Option D primarily causes central nervous system changes (confusion,
seizures) due to cellular swelling rather than isolated peripheral hyperreflexia.
Question 5
The nurse is reviewing the laboratory results of a patient with small cell lung
cancer who has developed Syndrome of Inappropriate Antidiuretic Hormone
(SIADH). Which lab finding requires immediate nursing intervention?
A. Serum sodium 142 mEq/L
B. Serum sodium 118 mEq/L
C. Serum osmolality 295 mOsm/kg
D. Urine specific gravity 1.005
CORRECT ANSWER: B. Serum sodium 118 mEq/L
RATIONALE: SIADH involves excessive release of antidiuretic hormone
(ADH) from either the posterior pituitary or an ectopic source (like small cell lung
cancer). This excess ADH causes the renal collecting ducts to reabsorb water
indiscriminately, expanding extracellular fluid volume and causing severe
dilutional hyponatremia. A serum sodium level of 118 mEq/L is critically low
(normal: 135–145 mEq/L) and puts the patient at extreme risk for cerebral edema,
increased intracranial pressure, seizures, coma, and death. Option A and C are
normal values. Option D reflects dilute urine, whereas SIADH causes highly
concentrated urine with a high specific gravity (typically >1.030).
Part II: Visual Assessment Tools in Electrolyte Pathophysiology
Question 6
