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Difficulty: MediumNeoplastic Processes

A 2424-year-old man is hospitalized for the treatment of newly diagnosed Burkitt lymphoma. He has a massive retroperitoneal tumor burden. Yesterday, he received his first cycle of systemic combination chemotherapy. Over the past 88 hours, his urine output has decreased to approximately 15 mL/hr15 \text{ mL/hr}. He reports mild nausea but denies muscle cramps, perioral numbness, or palpitations. Vital signs are stable. An electrocardiogram demonstrates a normal sinus rhythm with no PR or QT interval prolongation and normal T waves.

Laboratory evaluation reveals:
Potassium: 6.2 mEq/L6.2 \text{ mEq/L}
Uric acid: 14.8 mg/dL14.8 \text{ mg/dL}
Calcium: 6.2 mg/dL6.2 \text{ mg/dL}
Phosphorus: 9.5 mg/dL9.5 \text{ mg/dL}
Blood urea nitrogen: 45 mg/dL45 \text{ mg/dL}
Creatinine: 2.9 mg/dL2.9 \text{ mg/dL} (baseline 0.9 mg/dL0.9 \text{ mg/dL})

Based on the cellular consequences of this rapid neoplastic destruction, which of the following is the most appropriate next step in the management of this patient?

  1. Initiation of aggressive intravenous fluid hydration and administration of rasburicaseAnswer
  2. B
    Intravenous infusion of calcium gluconate to rapidly correct the measured hypocalcemia
  3. C
    Immediate placement of a hemodialysis catheter for emergent renal replacement therapy
  4. D
    Non-contrast computed tomography of the abdomen and pelvis to rule out ureteral obstruction
  5. E
    Initiation of oral allopurinol and implementation of a strict low-purine diet

Answer

The most appropriate next step is the initiation of aggressive intravenous fluid hydration and administration of rasburicase.
This patient is presenting with severe Tumor Lysis Syndrome (TLS) following the initiation of chemotherapy for a highly proliferative neoplastic process. The massive destruction of tumor cells releases large amounts of intracellular potassium, phosphorus, and nucleic acids into the systemic circulation. The nucleic acids are rapidly catabolized to uric acid, which, along with calcium phosphate, precipitates in the renal tubules and causes acute kidney injury. The most critical next step is aggressive intravenous hydration to maintain a high urine flow rate and the administration of rasburicase. Rasburicase is a recombinant urate oxidase enzyme that rapidly catalyzes the oxidation of uric acid into allantoin, a highly water-soluble compound, thereby quickly clearing the uric acid burden and preventing further renal tubular crystallization.

Step-by-Step Solution

1
Identify the clinical syndrome based on the patient's history and laboratory values.
The patient has a highly proliferative neoplasm (Burkitt lymphoma) and developed hyperkalemia, hyperuricemia, hyperphosphatemia, and hypocalcemia shortly after chemotherapy, which is diagnostic for Tumor Lysis Syndrome (TLS).
Recognizing TLS is crucial for initiating condition-specific emergency management.
2
Connect the neoplastic process to the pathophysiology of the acute renal failure.
Massive chemotherapy-induced lysis of neoplastic cells releases intracellular ions and nucleic acids, leading to precipitation of uric acid and calcium phosphate crystals in the renal tubules.
Understanding that the renal failure is intrinsic (tubular precipitation) rather than obstructive dictates the medical approach.
3
Select the optimal medical intervention to reverse the pathophysiologic cascade.
Aggressive intravenous hydration is required to flush the tubules, and rasburicase is needed to rapidly degrade existing uric acid.
Rasburicase acts rapidly to clear the massive existing uric acid burden, unlike preventive agents like allopurinol.

Key Concept

Management of Tumor Lysis Syndrome and contraindications for treating asymptomatic hypocalcemia in the setting of hyperphosphatemia.
Estimated Time:1m 15s
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Topics

Neoplastic Processes

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