What can prevent tumor lysis syndrome (TLS) in a patient with hyperkalemia, hypocalcemia, and hyperphosphatemia 24 hours post B cell lymphoma chemotherapy, with lab results showing normal sodium, elevated urea, and impaired renal function?

Prevention of Tumor Lysis Syndrome in B-Cell Lymphoma

Allopurinol (Option B) is the correct answer for preventing tumor lysis syndrome in patients with B-cell lymphoma undergoing chemotherapy, particularly for those at low-to-intermediate risk. 1

Understanding the Clinical Scenario

This patient presents with classic established tumor lysis syndrome (TLS) 24 hours post-chemotherapy, characterized by:

• Hyperkalemia (K=6) - from massive cell lysis releasing intracellular potassium 1
• Hypocalcemia - secondary to hyperphosphatemia and calcium-phosphate precipitation 1
• Hyperphosphatemia - from release of intracellular phosphate 1
• Acute kidney injury (Urea 570) - from uric acid crystallization and calcium-phosphate deposition 1

Why Allopurinol is the Preventive Agent

Allopurinol blocks xanthine oxidase, preventing conversion of hypoxanthine and xanthine to uric acid, thereby decreasing the risk of uric acid crystallization in the kidneys. 1

Evidence-Based Prevention Strategy:

For low-risk TLS patients:

• Hydration plus oral allopurinol is the recommended prophylaxis 1

For high-risk TLS patients (like B-cell lymphoma with bulky disease):

• Hydration plus rasburicase should be administered 1
• Rasburicase converts existing uric acid to allantoin, which is 5-10 times more soluble than uric acid 1

Why the Other Options Are Incorrect

Thiazide diuretics (Option A):

• Contraindicated - thiazides can worsen hyperuricemia and reduce renal excretion of uric acid 2
• Would exacerbate rather than prevent TLS

Furosemide (Option C):

• Loop diuretics are used to maintain urine output during TLS management (≥100 mL/hour in adults) 1
• They are adjunctive therapy, not primary prevention 1, 3
• Do not address the underlying hyperuricemia that drives TLS pathophysiology

Comprehensive TLS Prevention Algorithm

Risk Stratification First:

High-risk features in B-cell lymphoma include: 1

• Bulky disease (>10 cm)
• Elevated LDH (>2x upper limit of normal)
• High white blood cell count
• Pre-existing renal impairment
• Elevated baseline uric acid

Prevention Protocol:

For HIGH-RISK patients (most B-cell lymphomas): 1

• Aggressive IV hydration starting 48 hours before chemotherapy (target urine output ≥100 mL/hour)
• Rasburicase 0.20 mg/kg/day for 3-5 days, starting at least 4 hours before chemotherapy 4, 5
• Monitor labs every 6-12 hours for first 24-72 hours 6, 3

For LOW-RISK patients: 1

• IV hydration
• Allopurinol 300 mg/day orally (or 10 mg/kg/day in children)
• Close monitoring

Critical Management Pitfalls to Avoid

Do NOT alkalinize urine: 1, 3

• Increases calcium-phosphate precipitation risk
• Reduces xanthine solubility
• No longer recommended, especially with rasburicase availability

Do NOT give allopurinol with rasburicase concurrently: 4, 3

• Can cause xanthine accumulation
• Allopurinol should be discontinued when rasburicase is started

Do NOT treat asymptomatic hypocalcemia: 1, 3

• Risk of calcium-phosphate precipitation worsening renal injury
• Only treat if symptomatic (tetany, seizures) with calcium gluconate 50-100 mg/kg 1, 3

Monitoring Requirements for Prevention

Before chemotherapy initiation: 6, 3

• Baseline: uric acid, potassium, phosphorus, calcium, creatinine, BUN, LDH

During high-risk chemotherapy: 6, 3

• Every 6 hours for first 24 hours
• Every 12 hours for days 2-3
• Daily thereafter until stable

When Dialysis Becomes Necessary

Indications for urgent hemodialysis: 1, 3

• Persistent hyperkalemia despite medical management
• Severe hyperphosphatemia (>6 mg/dL) with progressive rise
• Oliguria/anuria unresponsive to diuretics
• Volume overload
• Symptomatic uremia (pericarditis, encephalopathy)

Hemodialysis effectively removes: 1

• Uric acid (clearance ~70-100 mL/min)
• Potassium
• Phosphate
• Reduces plasma uric acid by ~50% per 6-hour treatment

Real-World Clinical Application

In this specific case, the patient already has established TLS, so the question asks what could have prevented this presentation. The answer remains allopurinol prophylaxis initiated before chemotherapy, combined with aggressive hydration. 1 For a patient with B-cell lymphoma (typically high-risk), rasburicase would have been even more appropriate, but allopurinol is the only option listed that serves as TLS prophylaxis. 1