A 68-year-old man is brought to the emergency department by his daughter due to a 1-week h… — USMLE Step 2 CK

A 68-year-old man is brought to the emergency department by his daughter due to a 1-week history of progressively worsening lethargy, confusion, and severe mid-back pain. He has a past medical history of chronic obstructive pulmonary disease (COPD) and hypertension. For the past few days, he has also experienced severe constipation and increased urinary frequency. His temperature is $37.1^\circ\text{C}$ ( $98.8^\circ\text{F}$ ), blood pressure is $105/65\text{ mmHg}$ , heart rate is $108/\text{min}$ , and respiratory rate is $16/\text{min}$ . Physical examination reveals dry mucous membranes and diminished skin turgor. His lungs are clear to auscultation bilaterally. Neurologic examination shows a lethargic patient who is oriented only to person. There are no focal motor or sensory deficits. Initial laboratory studies show:

Laboratory test	Result
Hemoglobin	$8.4\text{ g/dL}$
Leukocyte count	$7,500/\mu\text{L}$
Platelet count	$160,000/\mu\text{L}$
Blood urea nitrogen	$65\text{ mg/dL}$
Serum creatinine	$3.2\text{ mg/dL}$
Serum calcium	$15.4\text{ mg/dL}$
Serum albumin	$3.6\text{ g/dL}$

Which of the following is the most appropriate initial step in the management of this patient?

A
Intravenous administration of furosemide
B
Intravenous administration of broad-spectrum antibiotics
C
Magnetic resonance imaging of the thoracic and lumbar spine
Intravenous administration of $0.9\%$ salineAnswer
E
Initiation of urgent hemodialysis

Answer

The most appropriate initial step in management is the intravenous administration of 0.9% saline.

The correct answer is the intravenous administration of

0.9\%

saline. This patient's presentation of bone pain, acute renal failure, severe hypercalcemia, and anemia is highly suspicious for multiple myeloma. Regardless of the underlying etiology, severe hypercalcemia (defined as serum calcium

> 14\text{ mg/dL}

) is a medical emergency. High serum calcium causes nephrogenic diabetes insipidus, leading to profound polyuria, dehydration, and prerenal acute kidney injury. The absolute most critical first step in management is aggressive volume expansion with isotonic (

0.9\%

) saline. This restores intravascular volume, improves the glomerular filtration rate (GFR), and directly promotes the urinary excretion of calcium.

Step-by-Step Solution

Identify the primary clinical emergency.

The patient has symptomatic, severe hypercalcemia (

15.4\text{ mg/dL}

) manifesting as lethargy, confusion, constipation, and profound volume depletion (hypotension, tachycardia, dry mucous membranes, prerenal acute kidney injury).

Severe hypercalcemia (

> 14\text{ mg/dL}

) is a life-threatening medical emergency requiring immediate intervention before pursuing definitive diagnostic workups for the underlying cause, which in this case is highly suspicious for multiple myeloma.

Determine the first-line treatment for severe hypercalcemia.

Aggressive intravenous hydration with isotonic (

0.9\%

) saline.

Hypercalcemia induces nephrogenic diabetes insipidus, leading to severe polyuria and volume depletion. Volume expansion with normal saline restores intravascular volume, increases the glomerular filtration rate, and directly promotes renal calcium excretion.

Evaluate and rule out other interventions.

Loop diuretics, hemodialysis, and diagnostic imaging are inappropriate at this exact moment.

Diuretics worsen volume depletion if given before fluids. Dialysis is reserved for refractory cases or volume-overloaded states. Imaging does not take precedence over hemodynamic stabilization.

Key Concept

The initial management of severe hypercalcemia of malignancy focuses on aggressive intravenous hydration with normal saline to restore intravascular volume and promote urinary calcium excretion.

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