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Difficulty: HardHematology and Oncology

On the oncology ward, nurses urgently call for a physician to evaluate a 48-year-old male patient. He was admitted 48 hours earlier to begin R-CHOP therapy for stage IV diffuse large B-cell lymphoma. Over the last several hours, he has developed profound leg weakness, palpitations, and decreased urine output. Vital signs show a heart rate of 115/min and blood pressure of 105/65 mm Hg. Examination reveals diminished deep tendon reflexes and generalized lethargy.

Stat laboratory testing reveals:

Laboratory TestResultReference Range
Sodium135 mEq/L136-145 mEq/L
Potassium7.5 mEq/L3.5-5.0 mEq/L
Chloride99 mEq/L98-106 mEq/L
Bicarbonate16 mEq/L22-28 mEq/L
Blood urea nitrogen52 mg/dL8-20 mg/dL
Creatinine3.4 mg/dL0.7-1.3 mg/dL
Calcium5.9 mg/dL8.4-10.2 mg/dL
Phosphorus9.2 mg/dL2.5-4.5 mg/dL
Uric acid17.1 mg/dL3.4-7.0 mg/dL

A 12-lead electrocardiogram demonstrates tall, tented T waves with loss of P waves and a widened QRS complex.

Which of the following is the most appropriate initial intervention for this patient?

  1. A
    Emergent hemodialysis preparation
  2. B
    Intravenous rasburicase
  3. C
    Intravenous regular insulin and dextrose
  4. Intravenous calcium gluconateAnswer
  5. E
    Intravenous sodium bicarbonate

Answer

The most appropriate initial intervention is intravenous calcium gluconate to immediately stabilize the cardiac membrane and prevent a fatal arrhythmia.
The patient is experiencing severe spontaneous tumor lysis syndrome (TLS), characterized by massive release of intracellular contents following chemotherapy for a rapidly proliferating malignancy. This results in hyperkalemia, hyperphosphatemia, hyperuricemia, and secondary hypocalcemia. The most immediate threat to this patient's life is severe hyperkalemia (potassium 7.5 mEq/L) with critical electrocardiographic changes (widened QRS complex, loss of P waves). The most appropriate initial intervention is intravenous calcium gluconate to stabilize the cardiac myocyte membrane and prevent fatal ventricular arrhythmias (e.g., ventricular fibrillation). While calcium does not lower serum potassium levels, it acts within minutes to antagonize the membrane effects of hyperkalemia. Other potassium-lowering therapies and uric acid management should follow sequentially.

Step-by-Step Solution

1
Diagnose the underlying syndrome based on history and laboratory findings.
The patient has Tumor Lysis Syndrome (TLS), characterized by severe hyperkalemia, hyperphosphatemia, hyperuricemia, hypocalcemia, and acute kidney injury following induction chemotherapy for a high-grade lymphoma.
Rapid tumor cell breakdown releases massive amounts of intracellular potassium, phosphate, and nucleic acids (which metabolize into uric acid) directly into the bloodstream.
2
Identify the most immediate life-threatening abnormality.
The most critical finding is severe hyperkalemia (7.5 mEq/L) accompanied by dangerous electrocardiographic changes (widened QRS complex, loss of P waves).
Severe hyperkalemia destabilizes the cardiac resting membrane potential and can rapidly progress to ventricular fibrillation or asystole.
3
Select the appropriate first-line intervention.
Administer intravenous calcium gluconate.
Calcium directly antagonizes the membrane actions of hyperkalemia, stabilizing the myocardium within minutes. This protects the heart while secondary measures to shift and eliminate potassium are prepared.

Key Concept

Management of Tumor Lysis Syndrome and severe hyperkalemia
Estimated Time:1m 30s
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Topics

Hematology and Oncology

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