The Metabolic Avalanche
Massive release of intracellular contents (, , Uric Acid) due to rapid tumour cell death.
high-risk populations
- Malignancies: Burkitt Lymphoma, Acute Lymphoblastic Leukaemia (ALL), high-grade lymphomas with bulky disease/high LDH.
- Trigger: Spontaneous or immediately following chemotherapy initiation.
prevention (prophylaxis)
- Hydration: Aggressive IV fluids aiming for 3 L//day (maintain high urine output). Avoid Ringer’s Lactate (contains potassium).
- Xanthine Oxidase Inhibitor: Allopurinol 300 mg PO daily (150 mg if renal failure). Prevents new uric acid formation.
active management
1. Urate Lowering (Rasburicase)
- Mechanism: Recombinant urate oxidase; degrades existing uric acid to soluble allantoin.
- Indication: High-risk prophylaxis or established TLS (elevated uric acid).
- Dosing (Centre Specific): 4.5 mg IV x 1 dose (Fixed dose, NOT weight-based). Repeat only if uric acid levels rebound.
critical lab trap
Blood samples for Uric Acid in patients who received Rasburicase must be placed on ICE immediately. Rasburicase continues to degrade uric acid ex vivo in the test tube at room temperature, causing a falsely low result.
2. Electrolyte Management
- Hyperkalaemia:
- Stabilise: Calcium Gluconate (cardioprotection).
- Shift: Insulin/Dextrose + Salbutamol (Ventolin).
- Eliminate: Loop diuretics (if volume replete) or Dialysis.
- Hyperphosphataemia: Phosphate binders (e.g., Sevelamer). Dialysis often needed.
- Hypocalcaemia:
- Treat only if symptomatic (tetany, seizures, arrhythmias). Calcium replacement promotes Ca-PO4 precipitation in kidneys (nephrocalcinosis).
monitoring
- Labs: Electrolytes, Creatinine, Calcium, Phosphate, Uric Acid q6-12h during induction.
- Strict fluid balance monitoring.