What lab parameters should be monitored in tumor lysis syndrome (TLS)?

Laboratory Parameters to Monitor in Tumor Lysis Syndrome (TLS)

In patients with tumor lysis syndrome, comprehensive laboratory monitoring should include uric acid, potassium, phosphorus, calcium, creatinine, BUN, and LDH, with monitoring frequency of every 6 hours for the first 24 hours and daily thereafter. 1

Definition of Laboratory TLS Parameters

Laboratory TLS is defined by abnormalities in the following parameters:

• Uric acid: Increase by >25% from baseline or values ≥476 mmol/L (8 mg/dL) 1
• Potassium: Increase by >25% from baseline or values ≥6.0 mmol/L (6 mEq/L) 1
• Phosphorus: Increase by >25% from baseline or values ≥1.45 mmol/L (4.5 mg/dL) in adults and ≥2.1 mmol/L (6.5 mg/dL) in children 1
• Calcium: Decrease by >25% from baseline or values ≤1.75 mmol/L (7 mg/dL) 1

Monitoring Protocol

For High-Risk Patients (Pre-TLS)

• Monitor the following parameters every 12 hours for the first three days, then every 24 hours subsequently 1:
  • LDH
  • Uric acid
  • Sodium
  • Potassium
  • Creatinine
  • BUN
  • Phosphorus
  • Calcium 1

For Patients with Established TLS

• Monitor the following parameters every 6 hours for the first 24 hours and daily thereafter 1:

  • Vital parameters (heart rate, blood pressure, urine output, respiratory rate)
  • Serum uric acid level
  • Serum electrolytes (phosphate, calcium, potassium)
  • Renal function (serum creatinine, BUN, urine pH and osmolality, urine specific gravity) 1

• Monitor the following parameters every 24 hours 1:

  • Complete blood count
  • Serum LDH
  • Albumin
  • Serum osmolality
  • Blood gases and acid-base equilibrium
  • Electrocardiogram
  • Body weight 1

Renal Function Assessment

• Reliable measurement of renal excretion function is essential 1
• While serum creatinine is widely used, it is a poor biomarker for acute kidney damage 1
• Creatinine clearance (requiring 24-hour urine collection) is an acceptable surrogate 1
• Estimated glomerular filtration rate (eGFR) can be calculated using:
  • MDRD formula: eGFR (mL/min/1.73 m²) = 175 × (serum creatinine (mmol/L) × 0.0113)^-1.154 × age (years)^-0.203 × (0.742 if female) 1
  • Cockroft-Gault equation: (140-age) × weight × 1.2 × (0.85 if female) / Serum creatinine 1

Clinical Significance of Laboratory Parameters

• Clinical TLS is defined by laboratory TLS plus at least one of: renal failure (eGFR ≤60 mL/min), cardiac arrhythmia, or seizure 1
• Hyperuricemia can lead to acute kidney injury due to crystal precipitation in renal tubules 2
• Hyperkalemia may cause cardiac arrhythmias and requires urgent intervention 2
• Hyperphosphatemia with secondary hypocalcemia can lead to tetany, seizures, and cardiac dysfunction 2

Pitfalls and Caveats

• Calcium gluconate should not be used to correct mild hypocalcemia as it may lead to increased tissue and renal precipitation of calcium phosphate 1
• Urine alkalinization is not recommended in patients receiving rasburicase therapy 1
• When using rasburicase, avoid concurrent administration of allopurinol to prevent xanthine accumulation 1
• Patients with G6PD deficiency should not receive rasburicase due to risk of hemolytic anemia 1
• Failure to monitor laboratory parameters frequently enough may result in missed opportunities for early intervention 1

By closely monitoring these laboratory parameters at the recommended intervals, clinicians can detect and address metabolic derangements early, potentially preventing progression to clinical TLS and improving patient outcomes.