What medication should be given to a lymphoma patient who develops oliguria after chemotherapy?

Rasburicase for Post-Chemotherapy Oliguria in Lymphoma

A lymphoma patient developing decreased urine output after chemotherapy should receive rasburicase (Option B), not thiazide diuretics or beta blockers, because this clinical presentation represents evolving tumor lysis syndrome (TLS) requiring immediate uric acid reduction to prevent acute kidney injury. 1

Clinical Recognition of Tumor Lysis Syndrome

This patient's presentation—lymphoma, recent chemotherapy exposure, and oliguria—constitutes the classic triad for evolving clinical TLS. 2, 1

• Oliguria after chemotherapy in lymphoma signals acute uric acid nephropathy until proven otherwise, particularly in high-grade lymphomas (Burkitt's, diffuse large B-cell, lymphoblastic) where massive tumor cell lysis releases purines that overwhelm renal clearance. 2, 1

• The decreased urine output reflects either uric acid crystal deposition in renal tubules or calcium-phosphate precipitation, both direct consequences of TLS. 2, 1

Why Rasburicase is the Correct Answer

Rasburicase enzymatically degrades existing uric acid into allantoin (5-10 times more soluble), achieving an 86% reduction in plasma uric acid within 4 hours—the only intervention that can reverse established hyperuricemia rapidly enough to salvage renal function. 1, 3

• In the pivotal randomized trial, rasburicase reduced uric acid by 86% at 4 hours versus only 12% with allopurinol (p<0.0001), and the mean uric acid area-under-curve was 128±70 mg·dL⁻¹·hour with rasburicase versus 329±129 mg·dL⁻¹·hour with allopurinol (p<0.001). 1, 3

• Retrospective pediatric data showed only 2.6% of rasburicase-treated patients required dialysis compared to 16% receiving allopurinol, demonstrating superior renal protection. 1

• The recommended dose is 0.20 mg/kg IV over 30 minutes daily for 3-5 days, with the first dose ideally given at least 4 hours before chemotherapy (though in this post-chemotherapy scenario, immediate administration is appropriate). 1, 4

Why the Other Options Are Wrong

Thiazide Diuretics (Option A) Are Contraindicated

• Thiazides worsen TLS by promoting volume depletion and concentrating uric acid in tubules, directly opposing the therapeutic goal of dilute, high-volume urine output. 1

• If diuresis is needed to achieve target urine output (≥100 mL/hour in adults), only loop diuretics—not thiazides—may be used, and only after confirming adequate hydration and ruling out obstructive uropathy. 1

• The correct supportive measure is aggressive IV hydration at 3 L/m²/day targeting urine output ≥100 mL/hour, not diuretic administration. 1

Beta Blockers (Option C) Have No Role

• Beta blockers address neither hyperuricemia nor the metabolic derangements of TLS (hyperkalemia, hyperphosphatemia, hypocalcemia). 2, 1

• While TLS can cause cardiac arrhythmias from hyperkalemia, the primary treatment is correcting the electrolyte abnormality—not rate control with beta blockers. 2

Critical Management Algorithm

Immediate Actions (Within 1 Hour)

1. Administer rasburicase 0.20 mg/kg IV over 30 minutes after confirming the patient is not G6PD-deficient, pregnant, or lactating. 1, 4

2. Initiate aggressive IV hydration at 3 L/m²/day (quarter-normal saline/5% dextrose without potassium, calcium, or phosphate) targeting urine output ≥100 mL/hour. 1

3. Draw baseline labs immediately: uric acid, creatinine, potassium, phosphorus, calcium, LDH—and place uric acid samples on ice to prevent ex vivo enzymatic degradation. 1

Monitoring and Redosing

• Recheck uric acid at 12-24 hours post-dose; redose rasburicase only if uric acid remains >4 mg/dL. 1

• Most patients require only 1-2 doses rather than the full 5-day course when uric acid is monitored appropriately. 1, 5

• After uric acid control, transition to oral allopurinol 100 mg/m² every 8 hours (maximum 800 mg/day) for 3-7 days—never give allopurinol concurrently with rasburicase due to xanthine accumulation risk. 1

Renal Replacement Therapy Threshold

• Prepare for urgent hemodialysis if oliguria persists despite rasburicase and hydration, or if hyperkalemia (>6.5 mEq/L), severe hyperphosphatemia (>10 mg/dL), or symptomatic hypocalcemia develops. 2, 1

Common Pitfalls to Avoid

• Do not give allopurinol instead of rasburicase when uric acid is already elevated—allopurinol only prevents new uric acid formation and cannot lower existing levels, leaving the patient at continued risk during the critical first 24-48 hours. 1, 6

• Do not alkalinize urine with sodium bicarbonate; this practice is no longer recommended because it promotes calcium-phosphate precipitation without clear benefit. 1

• Do not correct mild hypocalcemia with calcium gluconate unless the patient is symptomatic (tetany, seizures), as exogenous calcium accelerates calcium-phosphate crystal deposition in kidneys and soft tissues. 1

• Do not use thiazide diuretics in any TLS scenario—they concentrate urine and worsen crystal deposition. 1