In a patient with Burkitt lymphoma receiving B‑CHOP who develops tumor‑lysis syndrome with hyperkalemia, hypocalcemia and oliguria, what is the most appropriate therapy in addition to aggressive intravenous hydration?

Management of Tumor Lysis Syndrome with Oliguria and Severe Hyperkalemia

In this patient with Burkitt lymphoma receiving B-CHOP who has developed clinical tumor lysis syndrome with severe hyperkalemia (6 mmol/L), hypocalcemia, and oliguria, rasburicase (Option C) is the most appropriate management in addition to aggressive hydration. 1, 2

Rationale for Rasburicase as First-Line Therapy

The European Society for Medical Oncology and American Society of Hematology recommend aggressive intravenous hydration plus rasburicase immediately for patients with clinical tumor lysis syndrome to prevent life-threatening complications including acute renal failure, cardiac arrhythmias, seizures, and death. 1, 2

This patient meets criteria for clinical TLS based on:

• Laboratory abnormalities (hyperkalemia 6 mmol/L + hypocalcemia = ≥2 metabolic derangements) 1
• Clinical complication (oliguria/inability to urinate indicating acute kidney injury) 1, 2
• High-risk malignancy (Burkitt lymphoma has the highest TLS risk among all malignancies) 1

Why Rasburicase is Superior in This Clinical Context

• Rasburicase rapidly degrades uric acid within 4 hours, with 96% of patients achieving uric acid levels ≤2 mg/dL at 4 hours after the first dose 3
• The drug prevents complete renal shutdown and fatal hyperkalemia by immediately addressing the underlying pathophysiology of TLS 2
• Dosing is 0.2 mg/kg IV over 30 minutes immediately, continued for 3-5 days as needed 2

Why Loop Diuretics (Lasix) Are Contraindicated

The American College of Cardiology explicitly advises against using loop diuretics in patients with anuria or established oliguria despite adequate hydration. 1

Critical pitfalls with furosemide in this scenario:

• This patient has oliguria (unable to urinate), making loop diuretics ineffective and potentially harmful 1, 2
• Loop diuretics only play an adjunctive role to maintain urine output once adequate hydration is established—they should never be used as primary therapy 1
• In oliguric patients, furosemide will not enhance potassium excretion and delays definitive treatment 2

Why Thiazides Are Absolutely Contraindicated

Thiazide diuretics are contraindicated in TLS because they decrease uric acid excretion, potentially worsening hyperuricemia and precipitating uric acid nephropathy. 1

This makes Option B dangerous and completely inappropriate for TLS management.

Complete Management Algorithm Beyond Hydration

Immediate Interventions (First 30 Minutes)

1. Administer rasburicase 0.2 mg/kg IV over 30 minutes immediately 2, 3

2. Stabilize cardiac membrane for severe hyperkalemia (K+ = 6 mmol/L):

   • Calcium gluconate 50-100 mg/kg IV over 2-5 minutes (onset 1-3 minutes, duration 30-60 minutes) 1, 4, 2
   • This does not lower potassium but prevents arrhythmias 4

3. Lower serum potassium with combination therapy:

   • Rapid insulin 0.1 units/kg IV plus 25% dextrose 2 mL/kg IV (onset 15-30 minutes, duration 4-6 hours) 1, 4, 2

4. Initiate continuous ECG monitoring to detect hyperkalemia-induced arrhythmias 4, 2

Ongoing Management

• Maintain aggressive IV hydration at 3 L/m²/day targeting urine output ≥100 mL/hour 1, 2
• Do NOT administer allopurinol concurrently with rasburicase, as this causes xanthine accumulation and removes substrate for rasburicase 2
• Avoid treating asymptomatic hypocalcemia, as calcium administration can precipitate calcium-phosphate crystals in tissues and worsen renal injury 1

Indications for Urgent Hemodialysis

The American Society of Nephrology recommends initiating hemodialysis urgently when oliguria or anuria develops despite aggressive hydration. 1, 2

This patient likely requires dialysis given:

• Oliguria despite hydration 1, 2
• Severe hyperkalemia (6 mmol/L) 2
• Clinical TLS with renal failure 1

Hemodialysis is the most effective and reliable method for removing potassium from the body in refractory cases 4

Critical Monitoring Parameters

• Recheck potassium every 2-4 hours after initial treatment 1, 4, 2
• Monitor uric acid, electrolytes, phosphate, and calcium every 6 hours for the first 24 hours 1, 2
• Measure hourly urine output to assess response to therapy 1, 2
• Obtain immediate ECG to assess for peaked T waves, flattened P waves, prolonged PR interval, and widened QRS complex 4

Common Pitfall to Avoid

The most dangerous error would be choosing furosemide (Option A) in this oliguric patient, as it delays definitive rasburicase therapy and is ineffective when urine output is already compromised. Loop diuretics should only be considered after adequate hydration is established and urine output is restored—never in established oliguria. 1, 2