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Difficulty: MediumHematology and Oncology

A 5454-year-old man is hospitalized for the initiation of induction chemotherapy for a newly diagnosed high-grade non-Hodgkin lymphoma. Forty-eight hours after starting his chemotherapy regimen, he develops progressive lethargy, generalized muscle cramps, and two episodes of vomiting. His temperature is 37.2∘C37.2^\circ\text{C}, blood pressure is 105/65 mmHg105/65\text{ mmHg}, heart rate is 112/min112\text{/min}, and respiratory rate is 22/min22\text{/min}.

Laboratory studies reveal the following:

Laboratory TestResult
Potassium6.9 mEq/L6.9\text{ mEq/L}
Calcium6.1 mg/dL6.1\text{ mg/dL}
Phosphorus8.8 mg/dL8.8\text{ mg/dL}
Uric acid15.2 mg/dL15.2\text{ mg/dL}
Blood urea nitrogen48 mg/dL48\text{ mg/dL}
Creatinine2.9 mg/dL2.9\text{ mg/dL} (baseline 0.9 mg/dL0.9\text{ mg/dL})

An arterial blood gas analysis reveals a pH of 7.287.28, pCO2\text{pCO}_2 of 30 mmHg30\text{ mmHg}, and HCO3−\text{HCO}_3^- of 14 mEq/L14\text{ mEq/L}. An electrocardiogram demonstrates peaked T waves and a prolonged PR interval. Which of the following is the most appropriate next step in the management of this patient?

  1. A
    Administer intravenous sodium bicarbonate to correct the metabolic acidosis
  2. Administer intravenous calcium gluconate, vigorous hydration, and rasburicaseAnswer
  3. C
    Obtain a computed tomography scan of the abdomen and consult general surgery
  4. D
    Initiate broad-spectrum intravenous antibiotics and obtain blood cultures
  5. E
    Administer intravenous haloperidol and review the medication list for interactions

Answer

Administer intravenous calcium gluconate, vigorous hydration, and rasburicase
The correct answer involves immediate cardioprotection with calcium gluconate, followed by aggressive hydration and rasburicase. This patient is presenting with classic Tumor Lysis Syndrome (TLS), an oncologic emergency caused by massive tumor cell destruction following the initiation of cytotoxic therapy. The rapid breakdown of cells releases large amounts of intracellular potassium, phosphorus, and nucleic acids (which are metabolized to uric acid). The resulting hyperphosphatemia leads to secondary hypocalcemia as calcium binds to the excess phosphorus. The patient's electrocardiogram shows critical signs of hyperkalemia (peaked T waves and prolonged PR interval), making intravenous calcium gluconate the absolute most urgent first step to stabilize the cardiac membrane and prevent fatal arrhythmias. This must be given alongside aggressive intravenous hydration to maintain urine output and a potent urate-lowering agent like rasburicase to mitigate further acute kidney injury.

Step-by-Step Solution

1
Analyze the patient's clinical presentation and laboratory results in the context of recent chemotherapy.
The combination of hyperkalemia, hyperphosphatemia, hypocalcemia, hyperuricemia, and acute kidney injury 48 hours after starting chemotherapy points to Tumor Lysis Syndrome (TLS).
High-grade lymphomas are highly responsive to chemotherapy, leading to massive, rapid lysis of tumor cells and release of intracellular contents.
2
Evaluate the patient's electrocardiogram (ECG) and potassium levels.
The potassium is dangerously high (6.9 mEq/L6.9\text{ mEq/L}) with ECG changes (peaked T waves, prolonged PR interval).
ECG changes in the setting of hyperkalemia indicate imminent risk of fatal cardiac arrhythmias.
3
Determine the most appropriate immediate intervention based on the imminent threats to the patient's life.
The immediate priority is myocardial stabilization with intravenous calcium gluconate.
Calcium directly antagonizes the membrane actions of hyperkalemia without lowering the serum potassium level, buying time for therapies that drive potassium into cells or remove it from the body.
4
Identify the definitive management for the underlying pathophysiologic process of TLS.
The patient requires vigorous intravenous hydration and a urate-lowering agent such as rasburicase.
Hydration flushes the renal tubules, and rasburicase rapidly metabolizes existing uric acid into highly soluble allantoin, preventing further uric acid nephropathy and reversing the acute kidney injury.

Key Concept

Diagnosis and management of Tumor Lysis Syndrome (TLS)
Estimated Time:1m 30s
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Topics

Hematology and Oncology

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