A 68-year-old man is brought to the emergency department by his wife due to progressive co… — USMLE Step 2 CK

A 68-year-old man is brought to the emergency department by his wife due to progressive confusion, severe fatigue, and diffuse lower back pain over the past week. His wife reports he has had significantly diminished urine output for the last 3 days. His medical history is notable for a 40-pack-year smoking history and chronic obstructive pulmonary disease (COPD).

Vital signs are temperature 37.1°C (98.8°F), blood pressure 100/60 mmHg, heart rate 105/min, and respiratory rate 26/min. Pulse oximetry is 94% on room air.

Physical examination reveals pale conjunctivae and extremely dry mucous membranes. Pulmonary auscultation reveals distant breath sounds with faint scattered wheezes. The lower lumbar spine is tender to palpation.

Laboratory results are as follows:

Laboratory Test	Result	Reference Range
Hemoglobin	7.8 g/dL	13.5-17.5 g/dL
Leukocyte count	6,500/mm³	4,500-11,000/mm³
Platelet count	145,000/mm³	150,000-400,000/mm³
Calcium	13.8 mg/dL	8.5-10.5 mg/dL
Creatinine	4.5 mg/dL	0.6-1.2 mg/dL
Blood urea nitrogen	55 mg/dL	8-20 mg/dL
Total protein	10.5 g/dL	6.0-8.0 g/dL
Albumin	3.5 g/dL	3.5-5.0 g/dL
Thyroid-stimulating hormone (TSH)	0.2 µU/mL	0.4-4.0 µU/mL
Free thyroxine (T4)	0.8 ng/dL	0.9-1.7 ng/dL

Arterial blood gas on room air:

Parameter	Result
pH	7.25
$pCO_2$	35 mmHg
$pO_2$	65 mmHg
$HCO_3^-$	15 mEq/L

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

Initiate aggressive intravenous hydration with 0.9% sodium chlorideCevap
B
Administer intravenous sodium bicarbonate
C
Initiate noninvasive positive pressure ventilation
D
Administer intravenous cefepime and vancomycin
E
Initiate intravenous levothyroxine replacement

Cevap

Initiate aggressive intravenous hydration with 0.9% sodium chloride

This patient presents with the classic CRAB criteria for Multiple Myeloma (hyperCalcemia, Renal failure, Anemia, Bone pain). Furthermore, the substantial difference between total protein and albumin indicates a large gamma gap, typical of monoclonal gammopathy. He is presenting with an oncologic emergency: severe hypercalcemia of malignancy. Hypercalcemia induces a nephrogenic diabetes insipidus, leading to profound polyuria, dehydration, and a subsequent drop in glomerular filtration rate (GFR). This volume depletion worsens the acute kidney injury (often combined with light chain cast nephropathy in myeloma). The absolute most critical first step in management is aggressive intravenous hydration with isotonic saline (0.9% sodium chloride). Saline restores intravascular volume, increases GFR, and increases sodium delivery to the distal tubules, which inhibits calcium reabsorption and promotes calciuresis.

Adım Adım Çözüm

Analyze the classic tetrad of symptoms and lab findings.

The patient exhibits hypercalcemia (13.8 mg/dL), renal failure (Cr 4.5 mg/dL), anemia (Hb 7.8 g/dL), and bone pain, satisfying the CRAB criteria for Multiple Myeloma. The elevated total protein with normal albumin creates a gamma gap of 7.0 g/dL, confirming a monoclonal gammopathy.

Identifying the underlying oncologic diagnosis is necessary to understand the etiology of the acute presentation.

Identify the primary life-threatening derangement.

The patient is profoundly volume depleted (hypotension, tachycardia, dry mucous membranes) secondary to hypercalcemia-induced nephrogenic diabetes insipidus, which is simultaneously worsening his cast nephropathy and acute kidney injury.

Severe symptomatic hypercalcemia of malignancy is an oncologic emergency.

Determine the most appropriate immediate medical intervention.

Aggressive volume resuscitation with 0.9% sodium chloride (normal saline) is required to restore intravascular volume, improve the glomerular filtration rate (GFR), and promote the renal excretion of calcium.

Intravenous isotonic fluid is universally the first and most critical step in managing severe hypercalcemia, prior to administering targeted therapies like bisphosphonates or calcitonin.

Anahtar Kavram

The initial management of hypercalcemia of malignancy, particularly in the setting of Multiple Myeloma and acute kidney injury, is aggressive intravenous hydration with isotonic saline to restore intravascular volume and promote renal calcium excretion.

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