6 original SNLE questions on basic sciences, each with an explanation for all four options. Part of Nursing Fundamentals, worth 20% of the Saudi Nursing Licensure Examination.
Q01 / 06medium0 correct
Nursing Fundamentalsmediumq075
A 68-year-old patient with a history of chronic obstructive pulmonary disease (COPD) is admitted with increased dyspnea and confusion. Arterial blood gas results on room air are: pH 7.29, PaCO₂ 58 mm Hg, HCO₃⁻ 26 mEq/L. Which acid-base imbalance does the nurse interpret?
All 6 questions
Every question below, with the reasoning for all four options. Try to answer before you open one.
Basic sciences · medium
A 68-year-old patient with a history of chronic obstructive pulmonary disease (COPD) is admitted with increased dyspnea and confusion. Arterial blood gas results on room air are: pH 7.29, PaCO₂ 58 mm Hg, HCO₃⁻ 26 mEq/L. Which acid-base imbalance does the nurse interpret?
AUncompensated respiratory acidosis
BMetabolic acidosis with partial respiratory compensation
CMixed metabolic and respiratory acidosis
DCompensated respiratory alkalosis
Show the answer and why the others fail
Answer: A. Uncompensated respiratory acidosis
A — correct
The pH is <7.35 (acidosis), PaCO₂ is markedly elevated (normal 35–45 mm Hg), and HCO₃⁻ is within normal range (22–26 mEq/L), indicating the kidneys have not yet compensated. This matches acute hypoventilation from COPD exacerbation.
B
The pH is low (acidosis), but the primary disturbance is elevated PaCO₂, not low HCO₃⁻. HCO₃⁻ is normal, so this is not metabolic in origin.
C
A mixed disorder would show both low HCO₃⁻ (metabolic acidosis) and high PaCO₂ (respiratory acidosis). Here HCO₃⁻ is normal, so only respiratory acidosis is present.
D
The pH is acidotic, not alkalotic. In respiratory alkalosis, pH would be >7.45 and PaCO₂ would be low. This patient has a low pH and high PaCO₂.
TakeawayIn acute respiratory acidosis, the pH is low, PaCO₂ is high, and HCO₃⁻ is normal because renal compensation takes hours to days.
Basic sciences · medium
A nurse is caring for a patient with a traumatic brain injury who is showing signs of increased intracranial pressure. The healthcare provider prescribes an intravenous solution to reduce cerebral edema. Which of the following solutions should the nurse anticipate administering?
A3% sodium chloride
B0.45% sodium chloride
C0.9% sodium chloride
DLactated Ringer's solution
Show the answer and why the others fail
Answer: A. 3% sodium chloride
A — correct
3% sodium chloride is a hypertonic solution that increases the osmolarity of the blood, drawing water out of brain cells via osmosis and thereby reducing cerebral edema.
B
0.45% sodium chloride is hypotonic and would shift water into brain cells, worsening cerebral edema and increasing intracranial pressure.
C
0.9% sodium chloride is isotonic and will not create an osmotic gradient to pull fluid out of brain cells; it maintains current fluid distribution and does not reduce cerebral edema.
D
Lactated Ringer's is an isotonic solution that does not create an osmotic gradient to reduce cerebral edema; it is used for fluid resuscitation but not for treating cerebral edema.
TakeawayHypertonic solutions (e.g., 3% NaCl) are used to treat cerebral edema by creating an osmotic gradient that draws water out of brain cells.
Basic sciences · medium
A 45-year-old female patient is 2 days post-total thyroidectomy. She reports numbness and tingling around her mouth and in her fingertips. On assessment, the nurse notes a positive Trousseau's sign. Which electrolyte imbalance is most likely responsible for these findings?
AHypomagnesemia
BHyperkalemia
CHyponatremia
DHypocalcemia
Show the answer and why the others fail
Answer: D. Hypocalcemia
A
Hypomagnesemia can also cause neuromuscular irritability and tetany, but it is less directly linked to thyroidectomy; the scenario strongly suggests hypocalcemia from parathyroid disruption, which is the most common and immediate postoperative electrolyte disturbance.
B
Hyperkalemia primarily affects cardiac conduction and skeletal muscle, causing weakness, flaccid paralysis, and ECG changes such as peaked T waves, not tetany or paresthesias.
C
Hyponatremia typically causes neurological symptoms such as headache, confusion, seizures, and coma due to cerebral edema, not localized perioral or acral paresthesias and tetany.
D — correct
Hypocalcemia increases neuromuscular excitability, leading to paresthesias, muscle cramps, tetany, and positive Chvostek's and Trousseau's signs. It is a common complication after thyroidectomy due to parathyroid gland injury or removal.
TakeawayPost-thyroidectomy hypocalcemia due to parathyroid injury presents with neuromuscular irritability, including paresthesias and positive Trousseau's sign.
Basic sciences · medium
A 45-year-old patient with persistent vomiting for 4 days reports muscle cramps and tingling around the mouth. Arterial blood gas results: pH 7.49, PaCO₂ 47 mmHg, HCO₃⁻ 35 mEq/L. Which acid-base imbalance do these findings indicate?
AMetabolic alkalosis
BMetabolic acidosis
CRespiratory acidosis
DRespiratory alkalosis
Show the answer and why the others fail
Answer: A. Metabolic alkalosis
A — correct
The pH is elevated (alkalosis), the HCO₃⁻ is high (metabolic cause), and the PaCO₂ is slightly elevated as respiratory compensation for the metabolic alkalosis. Vomiting causes loss of gastric acid, leading to this imbalance.
B
Metabolic acidosis is characterized by low pH and low HCO₃⁻, not high pH and high HCO₃⁻ as seen here.
C
Respiratory acidosis presents with low pH and high PaCO₂, not high pH and high HCO₃⁻.
D
Respiratory alkalosis would show high pH and low PaCO₂, not high HCO₃⁻ and elevated PaCO₂.
TakeawayPersistent vomiting leads to metabolic alkalosis due to loss of gastric acid (HCl), resulting in elevated pH and HCO₃⁻.
Basic sciences · medium
A 22-year-old patient with type 1 diabetes mellitus presents to the emergency department with nausea, vomiting, and abdominal pain. The patient's respiratory rate is 28 breaths/min and deep. Arterial blood gas analysis reveals: pH 7.28, PaCO₂ 30 mm Hg, HCO₃⁻ 14 mEq/L. Which acid-base disturbance does the nurse interpret from these results?
ARespiratory acidosis
BRespiratory alkalosis
CMetabolic alkalosis
DMetabolic acidosis
Show the answer and why the others fail
Answer: D. Metabolic acidosis
A
Respiratory acidosis would show a low pH and elevated PaCO₂, but here the PaCO₂ is low, ruling out a primary respiratory cause.
B
Respiratory alkalosis would present with a high pH and low PaCO₂, but the pH here is low, indicating acidosis rather than alkalosis.
C
Metabolic alkalosis is characterized by an elevated pH and elevated HCO₃⁻, which is not present in this scenario.
D — correct
The pH is low (acidosis), the HCO₃⁻ is low (metabolic origin), and the PaCO₂ is low due to compensatory hyperventilation (Kussmaul respirations), consistent with metabolic acidosis.
TakeawayIn metabolic acidosis, the primary change is a decreased HCO₃⁻ causing a low pH, and the respiratory system compensates by lowering PaCO₂ through hyperventilation.
Basic sciences · medium
A 68-year-old patient with heart failure is taking furosemide 40 mg daily. The patient reports muscle weakness and cramping. The nurse suspects hypokalemia. Which of the following ECG changes would the nurse most likely observe?
APeaked T waves
BWide QRS complex
CProlonged PR interval
DProminent U wave
Show the answer and why the others fail
Answer: D. Prominent U wave
A
Peaked T waves are characteristic of hyperkalemia, not hypokalemia. In hyperkalemia, elevated serum potassium causes tall, narrow, peaked T waves, especially when potassium levels exceed 5.5 mEq/L.
B
Wide QRS complex is a late sign of severe hyperkalemia (usually >7.0 mEq/L) due to slowed conduction. Hypokalemia does not typically widen the QRS; instead, it may cause slight prolongation of the QT interval due to the prominent U wave merging with the T wave.
C
Prolonged PR interval (first-degree AV block) can occur with hyperkalemia, digoxin toxicity, or other conditions, but it is not a typical early ECG change of hypokalemia. Hypokalemia primarily affects the ST segment, T wave, and U wave.
D — correct
Hypokalemia delays ventricular repolarization, leading to ECG changes such as ST segment depression, flattened T waves, and a prominent U wave. The U wave is a positive deflection after the T wave and is a classic sign of hypokalemia.
TakeawayHypokalemia typically causes a prominent U wave on ECG, while hyperkalemia causes peaked T waves.