Tumor lysis syndrome (TLS) is a life-threatening oncologic emergency caused by the rapid release of intracellular contents (potassium, phosphate, nucleic acids) from lysing tumor cells, leading to hyperkalemia, hyperphosphatemia, hyperuricemia, and hypocalcemia. [1-2] In-hospital mortality ranges from 21% to as high as 79% in certain populations. [1] The following is a comprehensive clinical summary organized for emergency medicine and primary care workflows.
The pathophysiology of TLS is illustrated in the following figure from the NEJM review by Bociek and Lunning (2025):
1. History
- Key HPI questions: Ask about known malignancy type, recent chemotherapy or targeted therapy initiation (especially within 1–7 days), and any prior episodes of TLS [4-5]
- Symptom characterization: Nausea/vomiting, muscle cramps, tetany, palpitations, decreased urine output, cloudy/dark urine, lethargy, joint discomfort [6-7]
- Timing: Most commonly occurs 12–72 hours after initiation of cytotoxic therapy, but can occur spontaneously in high-burden malignancies [2][4]
- Important negatives: Absence of seizures, syncope, chest pain, or oliguria/anuria helps stratify severity
2. Alarm Features
- Seizures (from hypocalcemia or uremia) [3]
- Cardiac arrhythmias — peaked T waves, widened QRS, torsades de pointes [1][3]
- Oliguria/anuria — suggests acute kidney injury with possible need for emergent dialysis [8-9]
- Tetany, Trousseau/Chvostek signs — symptomatic hypocalcemia [9]
- Sudden cardiac arrest — hyperkalemia is the most immediately lethal electrolyte derangement [1]
- Hypotension or altered mental status — suggests multiorgan failure [9]
3. Medications
- Prophylaxis — Uric acid lowering (risk-stratified):
- Low risk: Allopurinol 300 mg/day PO (or febuxostat if allopurinol-intolerant), started 2–3 days before chemotherapy, continued 10–14 days [3][6]
- High risk: Rasburicase 3–6 mg IV single dose (or 0.1–0.2 mg/kg, max 6 mg); one dose is frequently adequate [3][6][8][10]
- Contraindications:
- Rasburicase is contraindicated in G6PD deficiency — risk of methemoglobinemia and hemolytic anemia. G6PD testing is required prior to use [6][8-9]
- Do NOT use calcium carbonate as a phosphate binder in TLS — promotes calcium phosphate crystal deposition [8-9]
- Urine alkalinization is no longer recommended [9][11-12]
- Hyperkalemia management: IV calcium gluconate (cardioprotection), insulin + glucose, beta-agonists, sodium polystyrene sulfonate, and dialysis if refractory [8-9]
- Hyperphosphatemia: Sevelamer (phosphate binder); avoid calcium-based binders [8-9]
- Lab pearl: If rasburicase is given, uric acid samples must be placed on ice immediately to prevent ex vivo degradation and falsely low readings [8-9]
4. Diet
- Phosphorus-restricted diet during active TLS management [8-9]
- Avoid potassium-containing foods and supplements
- Aggressive IV hydration is the cornerstone — 1.5–2× maintenance fluids (or 2–3 L/m²/day in adults), without potassium [8-9][11]
- Target urine output: ≥2 mL/kg/hr (pediatric) or ≥80–100 mL/hr (adult) [9]
5. Review of Systems
- Cardiovascular: Palpitations, chest pain, syncope (arrhythmia from hyperkalemia/hypocalcemia)
- Neurologic: Seizures, paresthesias, muscle cramps, tetany, altered mental status
- Renal/GU: Decreased urine output, dark/cloudy urine, flank pain
- GI: Nausea, vomiting, diarrhea, abdominal pain
- Musculoskeletal: Joint discomfort (uric acid deposition), muscle weakness
6. Collateral History and Family History
- Oncology team contact is essential — determine tumor type, stage, recent treatment, and TLS risk stratification already performed
- G6PD deficiency history — particularly in patients of African, Mediterranean, or Southeast Asian descent (critical before rasburicase) [6][8]
- Medication reconciliation — identify nephrotoxic agents (NSAIDs, contrast, aminoglycosides) that compound renal injury [3]
7. Risk Factors
- Highest-risk malignancies: Burkitt lymphoma, lymphoblastic lymphoma, ALL with high WBC (>100 × 10⁹/L) [4][9]
- High-risk features across malignancies:
- Bulky disease (>10 cm or >5 cm in CLL) [6][13]
- Elevated LDH (>2× ULN) [8-9]
- Bone marrow involvement (OR 13.78 in NHL) [14]
- Pre-existing elevated uric acid [6-7]
- Preexisting renal impairment or oliguria [8-9]
- Dehydration [8-9]
- Drug-specific risk: Venetoclax (BCL2 inhibitor) carries significant TLS risk requiring dose ramp-up protocol [13]
- Chemo-naïve patients are at higher risk than previously treated patients (prior chemo is protective, OR 0.44) [14]
8. Differential Diagnosis
- Acute kidney injury from other causes (contrast nephropathy, sepsis, obstruction)
- Sepsis — overlapping features of hypotension, AKI, and electrolyte derangements
- Rhabdomyolysis — similar electrolyte pattern (hyperkalemia, hyperphosphatemia, hypocalcemia, AKI); check CK
- Adrenal crisis — hyperkalemia, hypotension
- DKA — metabolic acidosis, electrolyte abnormalities
- Primary hyperkalemia from medications (ACE inhibitors, K-sparing diuretics, succinylcholine)
- Acute phosphate nephropathy (e.g., from phosphate-containing bowel preps)
9. Past Medical History
- Known malignancy type, stage, and treatment history
- Prior episodes of TLS
- Chronic kidney disease (lowers threshold for TLS complications)
- G6PD deficiency status
- Gout or baseline hyperuricemia
- Cardiac history (arrhythmia risk amplified by electrolyte shifts)
10. Physical Exam
- Vitals: Hypotension, tachycardia, tachypnea (Kussmaul breathing if acidotic)
- Cardiovascular: Irregular rhythm, signs of heart failure
- Neurologic: Hyperreflexia, Trousseau sign (carpal spasm with BP cuff inflation), Chvostek sign (facial twitching with tapping), seizure activity, altered sensorium
- Musculoskeletal: Muscle fasciculations, weakness, cramping
- Renal: Assess volume status (JVP, edema, skin turgor), bladder distension
- Abdominal: Hepatosplenomegaly, lymphadenopathy (tumor burden assessment)
11. Lab Studies
- Core TLS panel (q4–6h during active risk):
- Additional labs:
- LDH (tumor burden marker and TLS hallmark) [13]
- CBC with differential (WBC count for risk stratification)
- Magnesium
- ABG/VBG (metabolic acidosis assessment)
- Urinalysis (uric acid crystals, calcium phosphate crystals)
- CK (to exclude rhabdomyolysis)
- G6PD level (before rasburicase) [6]
- Cairo-Bishop laboratory TLS criteria (≥2 within 3 days before or 7 days after treatment): [3][15]
- Uric acid ≥8.0 mg/dL (adults) or >ULN (children), or 25% increase from baseline
- Phosphorus ≥4.5 mg/dL (adults) or ≥6.5 mg/dL (children), or 25% increase
- Potassium ≥6.0 mmol/L
- Corrected calcium <7.0 mg/dL or ionized calcium <4.5 mg/dL
12. Imaging
- Renal ultrasound — assess for hydronephrosis, renal parenchymal disease, or uric acid/calcium phosphate crystal deposition
- Chest X-ray — evaluate for pulmonary edema (fluid overload from aggressive hydration) or mediastinal mass
- CT chest/abdomen/pelvis — may be needed to assess tumor burden if not recently performed
- Imaging is generally secondary to laboratory monitoring in acute TLS management
13. Special Tests
- Cairo-Bishop Classification — the standard diagnostic and grading system for TLS: [1][3][15]
- Laboratory TLS: ≥2 metabolic abnormalities within 24 hours
- Clinical TLS: Laboratory TLS + ≥1 of: creatinine ≥1.5× ULN, cardiac arrhythmia/sudden death, or seizure
- Calcium-phosphate product: If >60 mg²/dL², high risk for calcium phosphate crystal deposition — avoid calcium supplementation [8-9]
- Point-of-care potassium (iSTAT/blood gas) — faster than serum in emergencies; also avoids pseudohyperkalemia from high WBC counts [13]
- Continuous cardiac monitoring — mandatory during active TLS [8-9]
14. ECG
- Hyperkalemia findings (most immediately dangerous):
- Hypocalcemia findings:
- Obtain ECG immediately in any patient with suspected TLS, and repeat with any significant potassium or calcium change
- Continuous telemetry is required for all patients with clinical TLS [8-9]
15. Assessment
TLS is a clinical and laboratory diagnosis based on the Cairo-Bishop criteria. [1][3] It most commonly occurs in hematologic malignancies with high tumor burden following initiation of effective therapy, but can occur spontaneously. [2][4] Severity ranges from asymptomatic laboratory abnormalities to multiorgan failure and death. The key complications are acute kidney injury (from uric acid and calcium phosphate crystal deposition), fatal cardiac arrhythmias (from hyperkalemia), and seizures (from hypocalcemia). [1][3][16]
16. Treatment Plan
Initial stabilization:
- IV hydration: Aggressive isotonic saline at 2–3 L/m²/day (adults) or 1.5–2× maintenance (pediatric), without potassium [8-9][11]
- Continuous cardiac monitoring and frequent electrolyte checks (q4–6h) [8-9]
Hyperuricemia management (risk-stratified):
The purine metabolism pathway and sites of drug action are illustrated below:
Electrolyte-specific management:
- Hyperkalemia: Remove exogenous K sources → IV calcium gluconate (cardioprotection) → insulin + dextrose → beta-agonists → kayexalate → dialysis if refractory [8-9]
- Hyperphosphatemia: Phosphorus-restricted diet + sevelamer. Do NOT use calcium carbonate (risk of calcium phosphate precipitation, especially if Ca × Phos product >60) [8-9]
- Hypocalcemia: Do NOT supplement calcium unless symptomatic (tetany, seizures, Trousseau/Chvostek signs) — asymptomatic correction can worsen calcium phosphate deposition [8-9]
Renal replacement therapy:
- hemodialysis or CRRTNCCN + 1[8-9]
A real-world propensity-matched study found rasburicase-treated patients had significantly lower TLS-associated mortality compared to allopurinol (2.1% vs. 7.1%, p = 0.047). [17]
17. Disposition
- Admit (ICU): Clinical TLS (lab TLS + AKI, arrhythmia, or seizure), symptomatic hyperkalemia, need for dialysis, hemodynamic instability [5]
- Admit (monitored bed): Laboratory TLS, high-risk patients initiating chemotherapy (e.g., Burkitt lymphoma, ALL with WBC >100K, venetoclax ramp-up) [9][13]
- Observation: Intermediate-risk patients with borderline labs after chemotherapy initiation
- Specialist consultation triggers:
- Nephrology: AKI, refractory electrolytes, dialysis consideration
- Oncology: All cases — coordinate treatment timing and TLS prophylaxis
- Cardiology: Significant arrhythmias
- ICU/Critical care: Hemodynamic instability, multiorgan failure, seizures
18. Follow Up / Return Precautions
- Inpatient monitoring: Continue electrolyte panels q4–6h until tumor burden is substantially decreased and labs are trending toward normal [9]
- Post-discharge: Recheck BMP, uric acid, LDH, and renal function within 24–48 hours of discharge
- Return precautions for patients/families:
- Decreased urine output, dark or bloody urine
- Muscle cramps, twitching, or weakness
- Palpitations, chest pain, or irregular heartbeat
- Confusion, seizures, or loss of consciousness
- Nausea/vomiting preventing oral hydration
- Expected course: Laboratory abnormalities typically peak 24–72 hours after treatment initiation and resolve within 5–7 days with appropriate management [2][4]
- Prevention for subsequent cycles: Risk-stratify before each cycle; patients who developed TLS should receive rasburicase prophylaxis for future treatments [6]
References
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