What are the characteristic electrolyte disturbances in Tumor Lysis Syndrome (TLS)?

Characteristic Electrolyte Disturbances in Tumor Lysis Syndrome

The characteristic electrolyte disturbances in Tumor Lysis Syndrome (TLS) are hyperkalemia, hyperphosphatemia, and hypocalcemia, along with hyperuricemia. 1

Pathophysiology of Electrolyte Abnormalities in TLS

Tumor Lysis Syndrome occurs when large numbers of malignant cells are rapidly destroyed, releasing their intracellular contents into the bloodstream. This overwhelming release exceeds the body's homeostatic mechanisms, resulting in specific metabolic derangements:

1. Hyperkalemia

   • Caused by massive release of intracellular potassium from lysed tumor cells
   • Can lead to cardiac arrhythmias and potentially death
   • Management includes hydration, loop diuretics, sodium polystyrene, and in severe cases, insulin with glucose, calcium carbonate, and sodium bicarbonate 1

2. Hyperphosphatemia

   • Results from release of intracellular phosphate
   • Can lead to calcium phosphate deposition in tissues and renal tubules
   • Can be treated with aluminum hydroxide when levels are >1.62 mmol/L 1

3. Hypocalcemia

   • Secondary to hyperphosphatemia (phosphate binds calcium)
   • Can cause tetany, seizures, and cardiac dysfunction
   • Symptomatic hypocalcemia requires calcium gluconate administration 1

4. Hyperuricemia

   • Results from breakdown of nucleic acids
   • Can lead to uric acid nephropathy and acute kidney injury
   • Managed with hydration and rasburicase or allopurinol 1, 2

Risk Factors and Prevention

High-risk patients include those with:

• Highly proliferative malignancies (e.g., acute lymphoblastic leukemia, Burkitt's lymphoma)
• Large tumor burden (≥500 g or ≥300 g/m² in children) 2
• High sensitivity to cytotoxic therapy

Management Approach

1. Preventive measures:

   • Aggressive hydration (starting 48 hours before chemotherapy when possible)
   • Maintain urine output of at least 100 mL/hour (3 mL/kg/hour in children <10 kg)
   • Rasburicase administration in high-risk patients 1

2. Treatment of established TLS:

   • Hydration through central venous access
   • Rasburicase for all patients with clinical TLS
   • Electrolyte-specific interventions as needed
   • Renal replacement therapy when indicated 1

Important Caveats

• Asymptomatic hypocalcemia does not require treatment, but symptomatic cases need prompt calcium gluconate administration
• ECG monitoring is essential in patients with hyperkalemia
• Xanthine can accumulate when using allopurinol, potentially causing additional complications 2
• TLS can rarely occur in solid tumors, not just hematologic malignancies 3

The correct answer to the multiple-choice question is A. Hyperkalemia, hyperphosphatasemia, & hypocalcemia, which accurately reflects the characteristic electrolyte disturbances in tumor lysis syndrome as documented in the consensus guidelines 1.