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Difficulty: HardGeneral Internal Medicine

Match each patient's clinical presentation and laboratory findings to the most appropriate initial therapeutic intervention.

  • A 65-year-old man with small cell lung cancer presenting with a generalized tonic-clonic seizure; serum sodium is 112 mEq/L.Hypertonic (3%) saline infusion
  • A 54-year-old woman with end-stage renal disease presenting with profound muscle weakness and widened QRS complexes on ECG; serum potassium is 7.6 mEq/L.Intravenous calcium gluconate
  • A 42-year-old man with squamous cell lung carcinoma presenting with lethargy and confusion; serum calcium is 15.2 mg/dL and blood urea nitrogen is 35 mg/dL.Aggressive isotonic (0.9%) saline hydration
  • A 72-year-old man with heart failure on high-dose loop diuretics presenting with polymorphic ventricular tachycardia; serum potassium is 3.1 mEq/L and magnesium is 0.9 mg/dL.Intravenous magnesium sulfate

Answer

The correct pairings match severe symptomatic hyponatremia to hypertonic saline, hyperkalemia with ECG changes to calcium gluconate, severe hypercalcemia to aggressive isotonic saline, and polymorphic ventricular tachycardia to magnesium sulfate.
Each clinical presentation describes a life-threatening complication of an electrolyte derangement that demands a specific, immediate pharmacological intervention. Symptomatic hyponatremia with seizures requires hypertonic saline to rapidly reduce cerebral edema. Hyperkalemia with widened QRS requires calcium gluconate to stabilize the resting membrane potential and prevent fatal ventricular fibrillation. Severe hypercalcemia causes nephrogenic diabetes insipidus and profound dehydration, necessitating aggressive isotonic saline hydration as the first step before administering any calcium-lowering agents. Polymorphic ventricular tachycardia (Torsades de pointes) associated with diuretic-induced hypomagnesemia requires immediate intravenous magnesium sulfate to stabilize the cardiac action potential.

Step-by-Step Solution

1
Assess the 65-year-old patient with a serum sodium of 112 mEq/L and new-onset seizures.
Diagnose severe symptomatic hyponatremia.
Seizures indicate critical cerebral edema, necessitating immediate hypertonic saline rather than standard fluid restriction.
2
Evaluate the 54-year-old patient presenting with a serum potassium of 7.6 mEq/L and widened QRS complexes.
Diagnose severe hyperkalemia with impending cardiac toxicity.
Widened QRS complexes are a precursor to fatal arrhythmias, requiring immediate myocardial membrane stabilization with calcium gluconate.
3
Analyze the 42-year-old patient with a serum calcium of 15.2 mg/dL and elevated blood urea nitrogen.
Diagnose severe hypercalcemia complicated by profound volume depletion.
Severe hypercalcemia causes nephrogenic diabetes insipidus; restoring intravascular volume with isotonic saline is the mandatory first therapeutic step.
4
Identify the rhythm in the 72-year-old patient with hypomagnesemia, hypokalemia, and polymorphic ventricular tachycardia.
Diagnose Torsades de pointes.
This specific arrhythmia in the setting of electrolyte depletion requires immediate intravenous magnesium sulfate to stabilize the cardiac action potential.

Key Concept

The initial pharmacological management of life-threatening electrolyte and acid-base emergencies prioritizes immediate physiological stabilization over definitive long-term correction.
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General Internal Medicine

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