What is the most appropriate management for a patient with lymphoma receiving B-Cell Chemotherapy (B-CHOP) who develops hyperkalemia, hypocalcemia, and impaired renal function (inability to urinate)?

Management of Tumor Lysis Syndrome with Anuria

This patient requires immediate rasburicase administration in addition to hydration, with urgent preparation for hemodialysis given the inability to urinate. The constellation of hyperkalemia, hypocalcemia, and anuria in a lymphoma patient receiving chemotherapy represents clinical tumor lysis syndrome (TLS) with acute kidney injury requiring aggressive intervention to prevent life-threatening cardiac arrhythmias and death 1.

Why Rasburicase (Option C) is the Correct Answer

Rasburicase should be administered immediately to all patients with clinical TLS, which is defined by the presence of at least 2 biochemical abnormalities (this patient has hyperkalemia and hypocalcemia) plus clinical complications such as renal failure. 1, 2

• Rasburicase rapidly degrades uric acid to allantoin within 4 hours, preventing further uric acid crystal deposition in the renal tubules and allowing potential recovery of renal function 3, 4
• The drug works at the end of the purine catabolic pathway and does not cause accumulation of xanthine or hypoxanthine, unlike allopurinol 4, 5
• In clinical trials, 96% of patients achieved uric acid levels ≤2 mg/dL within 4 hours of the first dose 3

Why Loop Diuretics (Lasix/Option A) are Contraindicated

Loop diuretics are absolutely contraindicated in this patient because they cannot urinate, indicating either severe hypovolemia or established acute kidney injury. 1, 6

• The guidelines explicitly state that loop diuretics should NOT be used in patients with anuria or oliguria despite adequate hydration 1
• Diuretics are only appropriate when patients can produce urine but need assistance maintaining the target output of ≥100 mL/hour 6
• Administering diuretics to an anuric patient will not restore urine output and may worsen the clinical situation 6

Why Thiazides (Option B) are Inappropriate

Thiazide diuretics have no role in TLS management and may actually worsen hypercalcemia. 2

• Thiazides are not mentioned in any TLS treatment guidelines 1, 2
• They are weaker diuretics than loop diuretics and would be even less effective in acute kidney injury
• Thiazides can cause hypercalcemia, which is counterproductive when managing electrolyte abnormalities 7

Complete Management Algorithm for This Patient

Immediate Actions (First 30 Minutes)

• Administer rasburicase 0.2 mg/kg IV over 30 minutes immediately 1, 3
• Continue aggressive IV hydration through central venous access (≥2 L/m²/day) 1, 6
• Obtain ECG immediately and initiate continuous cardiac monitoring for hyperkalemia-induced arrhythmias 1

Hyperkalemia Management Based on Severity

For severe hyperkalemia (≥6 mmol/L or any ECG changes): 1, 2

• Calcium gluconate 50-100 mg/kg IV over 2-5 minutes to stabilize myocardial membrane (this does NOT lower potassium but prevents cardiac arrest) 1, 2, 7
• Insulin 0.1 units/kg IV plus 25% dextrose 2 mL/kg IV (onset 15-30 minutes, duration 4-6 hours) 1, 2
• Sodium bicarbonate IV to correct acidosis and shift potassium intracellularly 1

For mild hyperkalemia (<6 mmol/L) without ECG changes: 1

• Sodium polystyrene sulfonate 1 g/kg orally or by enema 1
• Continue hydration (but this patient cannot urinate, so this is insufficient)

Urgent Dialysis Preparation

Contact nephrology immediately for urgent hemodialysis given anuria despite aggressive hydration. 2

• The American Society of Nephrology recommends initiating hemodialysis urgently when oliguria or anuria develops despite aggressive hydration 2
• Hemodialysis is also indicated for severe, refractory hyperkalemia (≥6 mmol/L unresponsive to medical management) 2
• This patient meets both criteria and will likely require dialysis within hours

Hypocalcemia Management

Do NOT treat asymptomatic hypocalcemia in TLS. 1

• Asymptomatic hypocalcemia does not require treatment 1
• Only treat if patient develops tetany, seizures, or prolonged QT interval with calcium gluconate 50-100 mg/kg IV 1
• Critical pitfall: Administering calcium when hyperphosphatemia is present (common in TLS) can cause calcium-phosphate precipitation in tissues and worsen renal function 1

Monitoring Parameters

• Recheck potassium every 2-4 hours after initial treatment 2
• Obtain comprehensive metabolic panel, phosphate, calcium, uric acid, LDH every 4-6 hours 2
• Monitor urine output hourly (though currently zero) 6
• Continuous ECG monitoring for arrhythmias 1

Critical Pitfalls to Avoid

Never alkalize urine in patients receiving rasburicase - this increases calcium phosphate precipitation risk without providing benefit since rasburicase rapidly degrades uric acid to allantoin 6

Never give calcium gluconate for hypocalcemia in the presence of hyperphosphatemia unless the patient is symptomatic - this can cause metastatic calcification and worsen renal function 1

Never delay dialysis in anuric patients - waiting for medical management to work when the kidneys have shut down increases mortality risk from hyperkalemia-induced cardiac arrest 2

Rasburicase is contraindicated in G6PD deficiency - it can cause severe hemolysis and methemoglobinemia in these patients 3, 8