Tumor lysis syndrome nursing: assessment, monitoring, and management

Tumor lysis syndrome (TLS) is a life-threatening oncologic emergency caused by the rapid breakdown of large numbers of malignant cells, releasing their intracellular contents into the bloodstream faster than the kidneys can clear them. It is the most common metabolic complication of cancer treatment and one of the highest-yield emergencies in NCLEX oncology content. Nurses caring for patients who have received cytotoxic chemotherapy — particularly for hematologic malignancies — must be able to recognize TLS early, monitor for its hallmark electrolyte abnormalities, and intervene quickly.

Feature	Key fact
Definition	Massive cell lysis releasing uric acid, potassium, phosphate, and nucleic acids
Highest-risk cancers	Burkitt lymphoma, ALL, AML with WBC >50,000/µL
Peak timing	First 12–72 hours after cytotoxic therapy initiation
Hallmark labs	↑ Uric acid, ↑ potassium, ↑ phosphate, ↓ calcium
Biggest nursing priority	Hyperkalemia → cardiac arrhythmia; hypocalcemia → tetany/seizure
Primary prophylaxis	Aggressive IV hydration + allopurinol or rasburicase
Cairo-Bishop classification	Lab TLS (≥2 electrolyte criteria) vs. clinical TLS (lab TLS + organ dysfunction)
Rasburicase contraindication	G6PD deficiency (causes hemolytic anemia) — check G6PD before giving

What is tumor lysis syndrome and why does it matter to nurses?

Tumor lysis syndrome occurs when cytotoxic therapy — or occasionally the tumor burden itself — destroys large numbers of malignant cells over a short period. Each cell ruptures and spills its intracellular contents into the extracellular space: potassium, phosphate, nucleic acids, and proteins flood the bloodstream simultaneously. The kidneys, which are already under stress from the malignancy, cannot excrete this load quickly enough. The result is a cascade of four dangerous electrolyte and metabolic derangements — hyperuricemia, hyperkalemia, hyperphosphatemia, and hypocalcemia — that can progress to acute kidney injury, cardiac arrhythmia, seizure, and death within hours.

For nurses, TLS matters because it is largely preventable and always time-sensitive. Risk stratification happens before chemotherapy starts, prophylaxis must be in place before the first dose, and monitoring must be continuous through the highest-risk window. Missing the early signs — a peaked T wave on telemetry, a dropping urine output, a rising creatinine — can mean the difference between a patient who completes their cancer treatment and one who does not survive the first cycle. See the oncology nursing reference for a broader framework of oncologic emergencies.

Pathophysiology: what happens when cancer cells lyse

The cascade begins with the simultaneous rupture of thousands to millions of malignant cells. Understanding what each cell contains — and what happens when that content floods the plasma — explains every clinical finding in TLS.

Nucleic acid release and uric acid production: Cancer cells have high intracellular concentrations of nucleic acids (DNA and RNA). When cells lyse, these are broken down to hypoxanthine and xanthine, then converted by xanthine oxidase to uric acid. In high-volume cell death, uric acid production outpaces renal clearance. Uric acid is poorly soluble in acidic environments — it crystallizes in the renal tubules and collecting ducts, causing obstructive nephropathy and acute kidney injury. This urate nephropathy further impairs the kidney’s ability to clear the remaining electrolyte excess, creating a downward spiral.

Potassium release: Potassium is the primary intracellular cation. Massive cell lysis delivers enormous potassium loads into the extracellular fluid rapidly. Even modest rises in serum potassium (above 5.5 mEq/L) begin to affect cardiac conduction. Severe hyperkalemia (above 6.5 mEq/L) can cause fatal ventricular fibrillation or asystole.

Phosphate release: Intracellular phosphate concentrations are three to four times higher than plasma concentrations. Rapid cell lysis floods the bloodstream with phosphate. Malignant cells — particularly lymphoblasts — have even higher phosphate loads than normal cells, making hyperphosphatemia especially severe in lymphoid malignancies. The kidneys excrete phosphate but cannot keep pace with massive acute loads. Elevated phosphate has a second dangerous consequence: it binds free calcium in the bloodstream, precipitating calcium-phosphate crystals in the renal tubules, vasculature, and soft tissues, and driving serum calcium down.

Hypocalcemia: The fall in calcium is not from reduced calcium intake but from phosphate-driven precipitation. As phosphate rises, the calcium-phosphate product increases. When this product exceeds solubility, calcium is pulled out of circulation and deposited as calcium-phosphate crystals. The result is symptomatic hypocalcemia — neuromuscular irritability, tetany, and seizure risk. Hypocalcemia also compounds the cardiac risk from hyperkalemia, since low ionized calcium impairs membrane stabilization.

The xanthine oxidase pathway is the primary mechanism linking cell lysis to uric acid accumulation. Allopurinol blocks this enzyme, preventing new uric acid formation. Rasburicase goes further — it converts existing uric acid to allantoin, which is far more soluble and rapidly excreted. This distinction determines which agent to use and when.

For renal consequences of TLS and the nursing management of acute kidney injury, see the AKI nursing guide.

Cairo-Bishop criteria: how TLS is formally classified

The Cairo-Bishop classification, published in 2004 and widely adopted, provides the standard diagnostic framework for TLS. It separates laboratory TLS from clinical TLS — an important distinction because clinical TLS requires more aggressive intervention and carries higher mortality.

Category	Definition	Clinical significance
Laboratory TLS	≥2 of the following within 3 days before or 7 days after chemotherapy initiation: • Uric acid ≥8 mg/dL (or 25% increase from baseline) • Potassium ≥6.0 mEq/L (or 25% increase from baseline) • Phosphate ≥4.5 mg/dL in adults (or 25% increase from baseline) • Calcium ≤7.0 mg/dL (or 25% decrease from baseline)	Metabolic derangement confirmed; clinical consequences may or may not be present
Clinical TLS	Lab TLS PLUS at least ONE of: • Serum creatinine ≥1.5× upper limit of normal (renal failure) • Cardiac arrhythmia or sudden death • Seizure	Organ dysfunction has occurred; mortality risk is significantly elevated; aggressive treatment required

The 25% change criterion is particularly important for NCLEX: a patient does not need to hit the absolute threshold values if their baseline was already low (for calcium) or high (for uric acid, potassium, phosphate). A patient with a baseline creatinine of 0.8 mg/dL whose creatinine rises to 1.2 mg/dL has not crossed the absolute threshold — but has had a 50% increase, which may signal early renal involvement.

Clinical TLS is a medical emergency. Lab TLS is a warning — it calls for intensified monitoring and treatment before organ dysfunction develops.

Risk stratification: who is most likely to develop TLS?

Not all cancer patients carry equal TLS risk. Stratification guides the aggressiveness of prophylaxis — who gets IV hydration alone, who gets allopurinol, and who gets rasburicase before treatment starts.

Risk level	Cancer types	Recommended prophylaxis
High risk	Burkitt lymphoma (all patients) ALL with high WBC or bulky disease AML with WBC >50,000/µL (blast crisis) CML in blast crisis Diffuse large B-cell lymphoma (DLBCL) with LDH >2× ULN + stage III/IV High-grade lymphoma with bulky disease	IV hydration + rasburicase before and during chemotherapy; continuous cardiac monitoring; electrolytes every 4–6 hours
Intermediate risk	DLBCL without high-risk features CLL with bulky disease or high WBC Multiple myeloma with renal impairment AML with WBC 25,000–50,000/µL Some solid tumors with large bulk and high proliferative index	IV hydration + allopurinol (started 1–2 days before chemo); electrolytes every 6–8 hours; cardiac monitoring
Low risk	Most solid tumors (breast, lung, colon, prostate) CLL with low disease burden Indolent lymphoma without bulky disease Multiple myeloma without renal impairment	IV hydration with close monitoring; no routine rasburicase or allopurinol required

Spontaneous TLS deserves special attention. TLS can occur before any chemotherapy is given, purely from the rapid natural turnover of highly proliferative malignant cells. Burkitt lymphoma is the classic example — patients may arrive in emergency with spontaneous TLS at diagnosis before treatment has started. This means any patient with a newly diagnosed high-risk hematologic malignancy should be evaluated for TLS at presentation, not just after chemotherapy begins.

For the nursing management of specific hematologic malignancies that carry the highest TLS risk, see leukemia nursing and lymphoma nursing.

The electrolyte tetrad: what happens to each lab value

The four hallmark electrolyte abnormalities of TLS each carry distinct clinical risks and require specific nursing monitoring and intervention strategies.

Electrolyte	Direction	Mechanism	Critical threshold	Clinical manifestations	Nursing priority
Uric acid	↑ Hyperuricemia	Nucleic acid breakdown via xanthine oxidase → uric acid crystals precipitate in renal tubules	≥8 mg/dL (or 25% rise)	Oliguria, flank pain, azotemia, gout-like joint pain (rare in TLS context)	Monitor urine output (target ≥100 mL/hr); check BUN/creatinine trends q4–6h; give allopurinol or rasburicase as ordered
Potassium	↑ Hyperkalemia	Massive intracellular K+ release; worsened by renal failure reducing K+ excretion	≥6.0 mEq/L (or 25% rise)	Peaked T waves, widened QRS, sine wave pattern, PVCs, ventricular fibrillation, muscle weakness, paralysis	Continuous cardiac telemetry; avoid K+ IV fluids; prepare calcium gluconate, insulin/dextrose, sodium bicarbonate, Kayexalate, dialysis as escalating options
Phosphate	↑ Hyperphosphatemia	Intracellular phosphate release; lymphoblasts have especially high phosphate content	≥4.5 mg/dL in adults (or 25% rise)	Usually asymptomatic itself; causes calcium-phosphate precipitation → worsens hypocalcemia and renal tubular injury	Administer phosphate binders (calcium carbonate, sevelamer) with meals as ordered; avoid phosphate-containing IV solutions; restrict dietary phosphate
Calcium	↓ Hypocalcemia	Phosphate binds calcium → precipitation; falling ionized calcium → neuromuscular and cardiac instability	≤7.0 mg/dL total calcium (or 25% fall); watch ionized Ca²⁺	Muscle cramps, tetany, perioral tingling, positive Chvostek/Trousseau signs, seizures, prolonged QT interval, laryngospasm	Assess Chvostek/Trousseau every 4–6h; seizure precautions; calcium gluconate IV for symptomatic hypocalcemia ONLY (do NOT give calcium routinely — worsens calcium-phosphate precipitation)

The critical NCLEX distinction for calcium: do NOT administer calcium supplements for asymptomatic hypocalcemia in TLS. Giving calcium when phosphate is still elevated increases the calcium-phosphate product and accelerates precipitation in the kidneys and vasculature. Reserve IV calcium gluconate for patients who are symptomatic — tetany, seizures, or hemodynamically significant arrhythmias from hypocalcemia.

For a full reference on electrolyte imbalances, their mechanisms, and nursing management, see electrolytes nursing and electrolyte imbalances nursing.

Prophylaxis: preventing TLS before it starts

The most effective TLS intervention is prophylaxis. High-risk patients should have prophylaxis in place before the first dose of cytotoxic therapy. Three core elements form the prophylaxis strategy: hydration, allopurinol, and (for high-risk patients) rasburicase.

Intervention	Mechanism	Dosing / administration	Key nursing considerations	Contraindications / cautions
IV hydration	Maintains high urine flow → flushes uric acid and electrolytes through renal tubules before crystals form; reduces uric acid concentration in filtrate	150–200 mL/hr normal saline; target urine output ≥100 mL/hr during high-risk period	Strict I&O; daily weights; monitor for fluid overload (edema, crackles, rising CVP); if urine output falls below 100 mL/hr despite fluids, escalate immediately	Use with caution in heart failure, severe renal impairment, or hypoalbuminemia with third-spacing risk
Allopurinol	Xanthine oxidase inhibitor — blocks conversion of hypoxanthine/xanthine to uric acid; prevents new uric acid production but does NOT clear existing uric acid	100–300 mg/m² per day orally (or IV for patients who cannot take PO); start 1–2 days before chemotherapy	Must be started BEFORE chemo to be effective; check renal dosing adjustments; may cause rash (rare Stevens-Johnson syndrome with azathioprine use)	Not effective for existing uric acid burden; accumulation of xanthine can still cause renal tubular damage (xanthine nephropathy)
Rasburicase	Recombinant uricase — converts uric acid to allantoin, which is 5–10× more water-soluble and rapidly renally cleared; reduces both new and existing uric acid	0.2 mg/kg IV daily (single or multiple doses depending on risk); onset of action within hours	Check G6PD status BEFORE giving — see below; rapid onset (uric acid begins falling within 4 hours); do NOT alkalinize urine (allantoin is more soluble at neutral/acidic pH)	CONTRAINDICATED in G6PD deficiency (causes severe hemolytic anemia and methemoglobinemia); also contraindicated in pregnancy

Why urinary alkalinization is no longer standard: Earlier protocols combined IV hydration with sodium bicarbonate to alkalinize the urine, under the theory that alkaline urine increases uric acid solubility and prevents crystal formation. Current guidelines have moved away from routine alkalinization for several reasons. Alkaline urine increases the risk of calcium-phosphate precipitation in the renal tubules (worsening hyperphosphatemia complications), and rasburicase-converted allantoin is actually more soluble at neutral or acidic pH. Alkalinization remains useful only in patients not receiving rasburicase with marked hyperuricemia — and only if phosphate levels are controlled.

G6PD and rasburicase — the essential safety check: Glucose-6-phosphate dehydrogenase (G6PD) deficiency is a red blood cell enzyme disorder most common in patients of African, Mediterranean, Southeast Asian, and Middle Eastern descent. When rasburicase metabolizes uric acid, hydrogen peroxide is generated as a byproduct. In patients with G6PD deficiency, the red blood cells cannot neutralize this oxidative stress, leading to acute hemolytic anemia and methemoglobinemia — a life-threatening reaction. G6PD status must be confirmed before rasburicase is given. A rapid G6PD screen is available; do not administer rasburicase until the result is known in patients from high-prevalence populations.

Treatment: managing established TLS

When TLS develops despite prophylaxis, treatment escalates across four parallel tracks: aggressive hydration, electrolyte correction, renal protection, and preparation for dialysis if needed.

Aggressive IV hydration

Continue or escalate IV fluid rates to maintain urine output ≥100 mL/hr. Normal saline is preferred (isotonic, no added potassium). If urine output is inadequate despite adequate volume, consider loop diuretics (furosemide) to drive renal excretion — but use only if the patient is volume-adequate. A patient who is dry from inadequate oral intake will not respond to diuretics and will suffer further renal ischemia.

Hyperkalemia management (most time-critical)

Hyperkalemia is the most immediately life-threatening electrolyte abnormality in TLS. The nurse’s role is cardiac monitoring and preparation for a stepwise response:

Continuous cardiac monitoring — identify peaked T waves (earliest sign), followed by PR prolongation, widened QRS, sine wave pattern (pre-arrest). Any change from baseline warrants immediate notification.
Calcium gluconate IV — cardiac membrane stabilization. Given when K⁺ ≥6.5 mEq/L with EKG changes or when arrhythmia is present. Does not lower potassium — it protects the heart while other agents work.
Insulin + dextrose — insulin drives potassium into cells; dextrose prevents hypoglycemia. Effect begins in 20–30 minutes, lasts 4–6 hours.
Sodium bicarbonate — in metabolic acidosis, alkalinization shifts K⁺ intracellularly. Less reliable in TLS than in isolated hyperkalemia.
Sodium polystyrene sulfonate (Kayexalate) or patiromer — ion exchange resin that removes potassium in the gut. Slower onset (hours), used for sustained potassium reduction.
Hemodialysis — required for severe, refractory hyperkalemia (K⁺ ≥7 mEq/L with EKG changes), or when the above measures fail.

For cardiac arrhythmia recognition and management in the context of electrolyte emergencies, see cardiac arrhythmias nursing.

Hyperphosphatemia management

Oral phosphate binders (calcium carbonate, sevelamer, lanthanum carbonate) are given with meals to bind dietary phosphate in the gut before it is absorbed. Avoid calcium-containing binders if calcium is already high (or if calcium-phosphate product is elevated). Restrict dietary phosphate intake. Phosphate-containing IV fluids (such as lactated Ringer’s solution in some formulations) should be avoided. For refractory hyperphosphatemia, dialysis removes phosphate effectively.

Hypocalcemia management

Symptomatic hypocalcemia (tetany, seizures, laryngospasm, hemodynamic instability) requires IV calcium gluconate 10% (not calcium chloride, which causes tissue necrosis if extravasated). Asymptomatic hypocalcemia should be monitored closely but not treated with calcium supplementation until phosphate is controlled — giving calcium into a high-phosphate environment worsens precipitation.

Hemodialysis indications in TLS

Dialysis is the definitive rescue therapy when the kidneys can no longer maintain electrolyte and fluid balance. Indications include:

Oliguria or anuria unresponsive to IV fluids and diuretics
Severe azotemia (BUN >80–100 mg/dL) or creatinine rising rapidly
Potassium ≥7 mEq/L with EKG changes
Refractory hyperphosphatemia causing symptomatic hypocalcemia
Fluid overload causing pulmonary edema in a patient with inadequate urine output
Uric acid ≥15 mg/dL with deteriorating renal function despite rasburicase

Nurses must anticipate dialysis needs early — notify nephrology at the first signs of oliguric renal failure, before the patient is in crisis.

Nursing monitoring: the surveillance framework

The first 72 hours of cytotoxic therapy in a high-risk patient require structured, proactive monitoring. Waiting for clinical deterioration to be obvious means TLS has already progressed further than it should.

Cardiac monitoring

All high-risk TLS patients should be on continuous cardiac telemetry. The nurse must recognize the EKG progression of hyperkalemia:

Peaked T waves: earliest sign; narrow, tall, symmetric T waves — most visible in precordial leads
Prolonged PR interval: impulse conduction slowing
Widened QRS: more severe hyperkalemia; conduction delay worsening
Sine wave pattern: fusion of widened QRS and T wave — immediately pre-arrest
Ventricular fibrillation or asystole: cardiac arrest

Any new EKG change in a patient receiving chemotherapy for a high-risk malignancy should trigger immediate potassium and calcium levels.

Hypocalcemia contributes to QTc prolongation, which increases the risk of torsades de pointes — a potentially fatal ventricular arrhythmia. Monitor QTc at every 12-lead EKG check.

Intake and output

Strict hourly I&O is mandatory. Urine output should be maintained at ≥100 mL/hr during the high-risk period (first 72 hours). A urine output below 100 mL/hr for two consecutive hours, despite adequate IV fluid rates, must be escalated immediately — this is early oliguric renal failure until proven otherwise. Daily weights detect fluid retention that may not yet be visible on exam.

Laboratory monitoring

Lab	Frequency in high-risk period	Critical values to report immediately
Serum potassium	Every 4–6 hours	≥6.0 mEq/L; any upward trend above 5.5 mEq/L
Serum phosphate	Every 4–6 hours	≥4.5 mg/dL; rapid rise
Serum calcium (total and ionized)	Every 4–6 hours	≤7.0 mg/dL total; symptomatic hypocalcemia at any level
Uric acid	Every 6–8 hours initially	≥8 mg/dL; rising despite rasburicase
Serum creatinine and BUN	Every 6–8 hours	Creatinine ≥1.5× baseline; oliguria with rising creatinine
Serum LDH	Daily	Rising LDH indicates ongoing tumor lysis
CBC with differential	Daily	WBC rise suggesting ongoing blast expansion

For critical lab value thresholds and nursing response protocols, see critical lab values nursing.

Neurological assessment

Hypocalcemia causes neuromuscular excitability. The nurse should assess every 4–6 hours:

Chvostek sign: Tap the facial nerve just anterior to the ear. A positive sign is ipsilateral facial muscle twitching — indicates latent tetany from hypocalcemia.
Trousseau sign: Inflate a blood pressure cuff above systolic for 3 minutes. Carpopedal spasm (wrist and fingers flexing into a characteristic posture) is a positive sign — more specific than Chvostek for hypocalcemia.
Perioral tingling and numbness: Often an early patient-reported symptom of falling ionized calcium.
Seizure precautions: Padded side rails, oxygen and suction at bedside, IV access confirmed, benzodiazepines available.

Vital signs and general assessment

Hourly or every-two-hour vital signs during the high-risk window. Blood pressure trends can reflect fluid status (hypovolemia from poor oral intake vs. fluid overload from aggressive hydration). Temperature monitoring for signs of infection (neutropenic patients receiving chemotherapy are at high infection risk concurrent with TLS risk). Respiratory assessment for pulmonary edema developing from fluid accumulation.

Timing: when is TLS most likely to occur?

Understanding the temporal pattern of TLS helps nurses prioritize vigilance appropriately:

Highest risk window: 12–72 hours after initiating cytotoxic therapy, as the first wave of tumor cell death peaks
Spontaneous TLS: May occur at diagnosis or presentation, before any treatment is given — particularly in Burkitt lymphoma and blast-phase leukemia
Sustained risk: In patients receiving prolonged induction chemotherapy (e.g., ALL induction over 28 days), the risk may extend beyond 72 hours whenever dose-dense cytotoxic therapy is given
Second peak: TLS can recur with subsequent chemotherapy cycles, though typically less severe if the initial tumor burden has been reduced
Delayed presentation: Occasionally, TLS peaks slightly later (day 3–5) in patients with slower tumor kinetics or compromised renal clearance — do not discontinue monitoring at 72 hours in patients with ongoing electrolyte derangements

Nursing diagnoses

The following nursing diagnoses are most relevant to TLS management:

Excess fluid volume related to aggressive IV hydration, oliguria, and renal tubular injury — evidenced by weight gain, edema, decreased urine output, and crackles on auscultation.

Risk for injury related to electrolyte imbalances — specifically hyperkalemia (cardiac arrhythmia risk), hyperphosphatemia (calcium-phosphate precipitation and worsening renal injury), and hypocalcemia (tetany, seizure, laryngospasm).

Impaired renal perfusion related to uric acid crystal deposition in renal tubules, calcium-phosphate precipitation, and decreased effective circulating volume — evidenced by rising creatinine, BUN, and decreasing GFR.

Activity intolerance related to electrolyte imbalances causing muscle weakness, fatigue, and arrhythmia risk — evidenced by weakness, inability to perform ADLs, and symptomatic hypotension on exertion.

Anxiety related to new diagnosis, intensive monitoring environment, and fear of life-threatening complications — evidenced by patient-reported worry, difficulty sleeping, and frequent questions about prognosis.

Patient and family education

Patients receiving cytotoxic chemotherapy for high-risk malignancies — and their families — need specific education about TLS before treatment begins, while they still have the cognitive and emotional capacity to absorb it. Timing education at the pre-treatment visit improves compliance with follow-up monitoring and early symptom reporting.

What to report immediately:

Decreased urine output — urinating less than usual, dark-colored urine, or no urine for several hours
Muscle cramps or spasms — especially in the hands, feet, or around the mouth (signs of hypocalcemia)
Palpitations or irregular heartbeat — any sense that the heart is racing, skipping, or fluttering (sign of hyperkalemia)
Numbness or tingling — especially around the lips or in the fingers (early hypocalcemia symptom)
Confusion, difficulty thinking, or seizures — neurological symptoms requiring immediate emergency response
Shortness of breath — may indicate fluid overload from IV hydration

Fluid intake guidance: Patients being treated with prophylactic IV hydration in an inpatient setting should understand why they are receiving large volumes of IV fluids and why fluid intake is being monitored so closely. For outpatient settings, patients should be advised to maintain high oral fluid intake and avoid NSAIDs and dehydration.

Follow-up monitoring: Emphasize that frequent blood draws and EKG checks during the first 72 hours are essential, not optional. Missing labs during this window can mean missing early warning signs when intervention is still straightforward.

Dietary guidance during treatment: Avoid foods high in potassium (bananas, oranges, potatoes, tomatoes) and phosphate (dairy, nuts, cola drinks) during the highest-risk period. Avoid alcohol and caffeine, which promote dehydration.

For a comprehensive framework of blood product and cytotoxic treatment monitoring, see blood transfusion nursing and multiple myeloma nursing.

20 NCLEX high-yield tips for tumor lysis syndrome

#	High-yield tip
1	TLS is most common after treatment of Burkitt lymphoma and ALL — these are the highest-risk cancers.
2	The four hallmark electrolyte abnormalities are: ↑ uric acid, ↑ potassium, ↑ phosphate, ↓ calcium. Remember: three go UP, one goes DOWN.
3	Cairo-Bishop lab TLS requires ≥2 electrolyte criteria within 3 days before or 7 days after chemotherapy. Clinical TLS = lab TLS + organ dysfunction (renal failure, arrhythmia, or seizure).
4	Peaked T waves are the earliest EKG sign of hyperkalemia — report immediately in any TLS patient.
5	The target urine output in TLS prophylaxis and treatment is ≥100 mL/hr. Falling below this threshold for two consecutive hours requires escalation.
6	Rasburicase is CONTRAINDICATED in G6PD deficiency — always check G6PD status before administering.
7	Rasburicase reduces EXISTING uric acid; allopurinol only prevents NEW uric acid formation. For high-risk patients, rasburicase is preferred.
8	Do NOT give calcium supplements for asymptomatic hypocalcemia in TLS — it worsens calcium-phosphate precipitation in the kidneys and vasculature.
9	Calcium gluconate IV is given for cardiac membrane stabilization in severe hyperkalemia — it does not lower the serum potassium level.
10	Allopurinol must be started 1–2 days BEFORE chemotherapy begins to be effective — it cannot work retroactively once uric acid has already accumulated.
11	Chvostek sign (facial twitch on tapping the facial nerve) and Trousseau sign (carpopedal spasm with BP cuff inflation) indicate latent tetany from hypocalcemia.
12	Urinary alkalinization with sodium bicarbonate is no longer routinely recommended in TLS — it increases calcium-phosphate precipitation risk and is unnecessary when rasburicase is used.
13	Spontaneous TLS can occur BEFORE chemotherapy in highly proliferative tumors like Burkitt lymphoma — check labs at diagnosis, not just after treatment starts.
14	Hypocalcemia prolongs the QTc interval, increasing torsades de pointes risk — monitor both potassium AND calcium on every EKG in TLS.
15	The sine wave EKG pattern (fusion of widened QRS and T wave) in hyperkalemia is immediately pre-arrest — prepare for emergency intervention.
16	Phosphate binders should be given WITH meals — not separately — to bind dietary phosphate in the gut before it is absorbed.
17	Normal saline (0.9% NaCl) is the preferred IV fluid in TLS — it contains no potassium, phosphate, or calcium. Avoid lactated Ringer's (contains potassium).
18	Dialysis is indicated for refractory hyperkalemia, severe azotemia, fluid overload with oliguria, or uric acid ≥15 mg/dL with worsening renal function.
19	The insulin/dextrose combination for hyperkalemia drives K⁺ into cells within 20–30 minutes — dextrose is given to prevent insulin-induced hypoglycemia, not to treat diabetes.
20	LDH (lactate dehydrogenase) is a marker of cell lysis — rising LDH in a cancer patient suggests active tumor breakdown and increasing TLS risk.

20 NCLEX scenario questions with answers and rationales

Summary

Tumor lysis syndrome is one of the most preventable oncologic emergencies nurses manage — but only when it is anticipated, stratified, and monitored proactively. The risk is highest in the first 12–72 hours after cytotoxic therapy for Burkitt lymphoma, ALL, and AML with hyperleukocytosis. The four hallmark abnormalities — hyperuricemia, hyperkalemia, hyperphosphatemia, and hypocalcemia — each carry specific nursing monitoring and intervention priorities. Aggressive IV hydration targeting ≥100 mL/hr of urine output is the cornerstone of management. Rasburicase, when G6PD status is confirmed safe, is the most effective uric acid-reducing agent available. Hyperkalemia with EKG changes requires immediate response; hypocalcemia with symptoms requires calcium gluconate — but never in a patient with uncontrolled hyperphosphatemia unless symptoms are present. Dialysis must be anticipated early, not considered only as a last resort.

Nurses who understand the mechanism behind each electrolyte derangement, know the Cairo-Bishop criteria, and can recognize EKG changes of hyperkalemia early will identify TLS at a stage where intervention remains straightforward and effective.

For related oncology nursing topics, see leukemia nursing, lymphoma nursing, electrolytes nursing, and AKI nursing.

#	Question	Answer	Rationale
1	A patient with Burkitt lymphoma is 18 hours into induction chemotherapy. Labs show K⁺ 6.2 mEq/L, phosphate 5.1 mg/dL, uric acid 9.4 mg/dL, and calcium 6.8 mg/dL. Which complication requires the MOST immediate nursing intervention? A) Hyperphosphatemia B) Hyperkalemia C) Hyperuricemia D) Hypocalcemia	B) Hyperkalemia	Hyperkalemia at 6.2 mEq/L with EKG monitoring required is the most immediately life-threatening abnormality — cardiac arrhythmias can develop rapidly. While all four are present (meeting lab TLS criteria), potassium elevation poses the most acute cardiac risk and requires the fastest response.
2	The nurse is caring for a patient receiving rasburicase for TLS prophylaxis. Which assessment finding should the nurse report to the provider IMMEDIATELY? A) Uric acid level 3.2 mg/dL (down from 9.1 mg/dL) B) Urine output 140 mL/hr C) New onset of jaundice and dark-colored urine D) Mild perioral tingling	C) New onset of jaundice and dark-colored urine	Jaundice and dark urine in a patient receiving rasburicase suggest hemolytic anemia — a life-threatening reaction that occurs in patients with undetected G6PD deficiency. Rasburicase generates hydrogen peroxide during uric acid metabolism; G6PD-deficient RBCs cannot neutralize this oxidative stress and lyse. This is a medical emergency.
3	A patient with AML (WBC 68,000/µL) is starting induction chemotherapy. Allopurinol was ordered. When should the nurse administer the first dose? A) Immediately after the first chemotherapy dose B) 1–2 days before chemotherapy begins C) At the first sign of rising uric acid D) Only if uric acid exceeds 8 mg/dL	B) 1–2 days before chemotherapy begins	Allopurinol works by blocking xanthine oxidase, preventing new uric acid formation. It has no effect on uric acid already in circulation. To be effective in preventing TLS-related uric acid accumulation, it must be started before the chemotherapy-induced cell lysis begins. Starting after chemotherapy provides insufficient protection.
4	The telemetry nurse observes the following EKG changes in a TLS patient: narrow, symmetrically peaked T waves in V3–V5. Which action should the nurse take FIRST? A) Administer oral potassium supplement B) Obtain a STAT serum potassium level C) Prepare to administer a defibrillation shock D) Increase the IV fluid infusion rate	B) Obtain a STAT serum potassium level	Peaked T waves are the earliest EKG sign of hyperkalemia. The priority is to confirm the diagnosis with a STAT potassium level so treatment can be appropriately targeted. Defibrillation is for ventricular fibrillation, not peaked T waves. Oral potassium is contraindicated. IV fluids alone will not correct hyperkalemia.
5	A patient in TLS has a serum calcium of 6.4 mg/dL (low) and a serum phosphate of 6.8 mg/dL (high). The nurse receives an order to administer calcium gluconate IV. What is the nurse's BEST response? A) Administer the calcium gluconate as ordered B) Clarify whether the patient is symptomatic before administering C) Refuse the order and document the refusal D) Administer calcium carbonate orally instead	B) Clarify whether the patient is symptomatic before administering	Calcium supplementation in TLS should be reserved for symptomatic hypocalcemia. When phosphate remains elevated, giving calcium increases the calcium-phosphate product, worsening precipitation in the kidneys and vasculature. The nurse should clarify the patient's symptoms (tetany, seizures, cardiac instability) before administering — an appropriate safety clarification, not a refusal.
6	A nurse is assessing a patient with TLS-related hypocalcemia. Which finding would the nurse expect? A) Hypertension and bradycardia B) Flaccid muscle paralysis C) Positive Trousseau sign D) Hyperreflexia and flushing	C) Positive Trousseau sign	Trousseau sign — carpopedal spasm elicited by inflating a blood pressure cuff above systolic for 3 minutes — is a classic indicator of latent tetany from hypocalcemia. Hypocalcemia causes neuromuscular excitability (not flaccid paralysis, which occurs with hyperkalemia-related weakness). Flushing is not associated with hypocalcemia.
7	A patient with CLL (bulky lymphadenopathy) is due to start chemotherapy tomorrow. The nurse notes the pre-treatment uric acid is 9.8 mg/dL. Which intervention would the nurse anticipate? A) Hold chemotherapy and recheck labs in 1 week B) Administer allopurinol after the first chemotherapy dose C) Administer rasburicase IV prior to chemotherapy and check G6PD status D) Restrict IV fluids to prevent fluid overload	C) Administer rasburicase IV prior to chemotherapy and check G6PD status	A pre-treatment uric acid of 9.8 mg/dL already meets lab TLS criteria for uric acid (≥8 mg/dL). In this high-burden situation, rasburicase is preferred over allopurinol because it can reduce existing uric acid rapidly (rasburicase converts uric acid to allantoin; allopurinol only prevents new uric acid formation). G6PD status must be confirmed before rasburicase is given.
8	A patient receiving TLS prophylaxis has a urine output of 70 mL over the past hour despite receiving IV normal saline at 175 mL/hr. What is the nurse's priority action? A) Increase the IV fluid rate to 250 mL/hr without notifying the provider B) Document the finding and recheck in one hour C) Notify the provider of oliguria and assess for signs of renal failure D) Administer furosemide without an order to promote urine flow	C) Notify the provider of oliguria and assess for signs of renal failure	Urine output below 100 mL/hr in a TLS patient indicates that renal clearance is inadequate. This is a critical threshold — falling below it suggests early oliguric renal failure from uric acid or calcium-phosphate crystal deposition. Notifying the provider and assessing for renal failure (rising creatinine, BUN) is the appropriate priority. Independently adjusting fluids or diuretics without an order is outside nursing scope.
9	The nurse is preparing to administer insulin and dextrose IV for hyperkalemia in a TLS patient. What is the PRIMARY rationale for including dextrose in this regimen? A) Dextrose provides energy to the weakened myocardium B) Dextrose prevents hypoglycemia caused by the insulin dose C) Dextrose helps shift potassium into the renal tubules for excretion D) Dextrose alkalinizes the urine to enhance potassium clearance	B) Dextrose prevents hypoglycemia caused by the insulin dose	Insulin drives potassium into cells by stimulating the Na⁺/K⁺-ATPase pump — this is the mechanism of action. The dextrose is given solely to prevent insulin-induced hypoglycemia, not as a therapeutic agent for hyperkalemia itself. Blood glucose should be monitored after the regimen.
10	Which patient requires the MOST urgent TLS monitoring at hospital admission, before any treatment has been given? A) A 65-year-old with stage I CLL presenting for a routine oncology follow-up B) A 22-year-old with newly diagnosed Burkitt lymphoma presenting with a WBC of 95,000/µL C) A 70-year-old with colon cancer receiving first-cycle FOLFOX D) A 55-year-old with breast cancer receiving adjuvant taxane therapy	B) A 22-year-old with newly diagnosed Burkitt lymphoma with WBC 95,000/µL	Burkitt lymphoma is the highest-risk cancer for spontaneous TLS — the rapidly proliferating cells lyse spontaneously without any treatment trigger. A WBC of 95,000/µL indicates massive tumor burden. This patient may already have lab TLS at presentation. Immediate electrolyte and uric acid labs are essential before any treatment decision is made.
11	The nurse assesses a patient with TLS and notes positive Chvostek sign. Which medication should the nurse prepare to administer if symptoms progress? A) IV potassium chloride B) IV calcium gluconate C) IV sodium bicarbonate D) IV magnesium sulfate	B) IV calcium gluconate	Positive Chvostek sign indicates latent tetany from hypocalcemia. If the patient progresses to symptomatic hypocalcemia (overt tetany, carpopedal spasm, laryngospasm, or seizures), IV calcium gluconate is the treatment of choice. Calcium chloride is avoided peripherally due to tissue necrosis risk if extravasated. Calcium gluconate is the safer peripheral preparation.
12	A patient with TLS has a potassium of 7.1 mEq/L and the EKG shows a sine wave pattern. Which intervention has the HIGHEST priority? A) Administer sodium polystyrene sulfonate (Kayexalate) orally B) Administer IV calcium gluconate immediately C) Place the patient on telemetry monitoring D) Increase IV fluids to 200 mL/hr	B) Administer IV calcium gluconate immediately	The sine wave pattern represents a pre-arrest EKG — this is a cardiac emergency. Immediate IV calcium gluconate stabilizes the cardiac membrane and buys time for definitive potassium-lowering measures. The patient should already be on telemetry. Kayexalate works over hours and is not an emergency intervention. IV fluids do not address cardiac conduction instability.
13	A patient is receiving IV normal saline at 175 mL/hr for TLS prophylaxis. After 12 hours, the nurse notes 3+ bilateral pitting edema and crackles in the lung bases bilaterally. Urine output has been 130 mL/hr. What is the nurse's BEST action? A) Continue fluids at the same rate and recheck in 4 hours B) Stop the IV fluids immediately C) Notify the provider and assess for early pulmonary edema D) Reduce IV fluids to 75 mL/hr without notifying the provider	C) Notify the provider and assess for early pulmonary edema	Bilateral crackles and pitting edema in a patient receiving aggressive IV hydration suggest fluid overload and possible early pulmonary edema — a serious complication of TLS hydration therapy. The nurse cannot independently modify IV fluid rates significantly without a provider order. Notifying the provider with full assessment data is the correct priority action.
14	Which IV solution is MOST appropriate for a patient receiving aggressive hydration for TLS? A) 0.45% sodium chloride with 20 mEq/L potassium B) Lactated Ringer's solution C) 0.9% sodium chloride (normal saline) D) 5% dextrose in water (D5W)	C) 0.9% sodium chloride (normal saline)	Normal saline (0.9% NaCl) is the preferred fluid in TLS because it contains no potassium, phosphate, or calcium — avoiding any addition to the already-elevated electrolyte burden. Lactated Ringer's contains potassium and lactate. D5W is hypotonic after glucose metabolism and provides inadequate volume expansion. Potassium-containing solutions are specifically contraindicated in hyperkalemia.
15	When should the nurse administer phosphate binder medications to a TLS patient? A) At bedtime to allow overnight absorption B) With meals, to bind dietary phosphate in the gut C) Between meals to maximize systemic availability D) Immediately after dialysis	B) With meals, to bind dietary phosphate in the gut	Phosphate binders (calcium carbonate, sevelamer, lanthanum carbonate) work by binding phosphate in the gastrointestinal tract before it can be absorbed into the bloodstream. To be effective, they must be present in the gut at the same time as dietary phosphate — which means administering with meals. Taking them between meals provides no phosphate-binding benefit.
16	A TLS patient develops a serum potassium of 6.8 mEq/L. The provider orders sodium bicarbonate IV. Under which condition is this intervention MOST effective? A) When the patient has concurrent respiratory alkalosis B) When the patient has concurrent metabolic acidosis C) When the patient is receiving calcium supplementation D) When urine output exceeds 150 mL/hr	B) When the patient has concurrent metabolic acidosis	Sodium bicarbonate shifts potassium into cells by correcting acidosis — in acidosis, K⁺ shifts out of cells in exchange for H⁺. Correcting the acidosis reverses this. If pH is already normal or alkalotic, sodium bicarbonate provides limited benefit for hyperkalemia and risks causing metabolic alkalosis, which worsens calcium ionization and hypocalcemia symptoms.
17	A nurse is explaining TLS monitoring to a patient with newly diagnosed ALL who will start chemotherapy in 2 days. Which patient statement indicates a NEED for further teaching? A) "I should tell you right away if I notice my urine output decreasing." B) "Muscle cramps in my hands could be a sign of low calcium." C) "I can eat bananas and drink orange juice to keep my potassium up." D) "I'll need frequent blood draws in the first few days after starting chemo."	C) "I can eat bananas and drink orange juice to keep my potassium up."	Bananas and orange juice are high-potassium foods — exactly what a high-risk TLS patient should avoid during the highest-risk period. The patient's potassium will rise, not fall, in TLS. Additional potassium from dietary sources worsens hyperkalemia and cardiac risk. The other statements reflect accurate understanding of TLS monitoring and symptoms.
18	A patient with TLS has the following labs: creatinine 2.8 mg/dL (baseline 0.9 mg/dL), K⁺ 7.2 mEq/L, phosphate 7.1 mg/dL, urine output 20 mL/hr for the past 3 hours. Which intervention should the nurse prioritize? A) Prepare for hemodialysis consultation B) Administer oral sodium polystyrene sulfonate (Kayexalate) C) Increase IV fluid rate to 300 mL/hr D) Place the patient in a supine position	A) Prepare for hemodialysis consultation	This patient has clinical TLS with severe oliguric renal failure (creatinine >3× baseline), life-threatening hyperkalemia, and severe hyperphosphatemia — all uncontrolled and with markedly reduced urine output. These meet multiple dialysis indications. While other interventions (calcium gluconate for cardiac protection, positioning for hemodynamics) are also appropriate, the priority action is escalating to nephrology for emergent dialysis.
19	The provider asks the nurse to check a G6PD level before rasburicase administration. Which patient characteristic MOST increases the need for this safety check? A) Age over 65 years B) Female sex C) West African ancestry D) History of diabetes mellitus	C) West African ancestry	G6PD deficiency is an X-linked recessive disorder with highest prevalence in populations of African, Mediterranean, Middle Eastern, and Southeast Asian descent. West African ancestry represents one of the highest-prevalence populations globally (affecting approximately 10–20% of males). G6PD deficiency must be confirmed before rasburicase is given in patients from these groups. Age and diabetes are not risk factors for G6PD deficiency.
20	A nurse reviews the morning labs on a patient who started AML induction chemotherapy 36 hours ago: uric acid 8.3 mg/dL, K⁺ 6.1 mEq/L, phosphate 4.6 mg/dL, calcium 7.2 mg/dL, creatinine 1.1 mg/dL (baseline 0.9 mg/dL). How should the nurse classify this patient? A) Clinical TLS — requires dialysis B) Lab TLS — requires intensified monitoring and electrolyte management C) No TLS — labs are within acceptable range D) Clinical TLS — arrhythmia treatment required	B) Lab TLS — requires intensified monitoring and electrolyte management	All four electrolyte criteria are met or exceeded (uric acid ≥8, K⁺ ≥6.0, phosphate ≥4.5, calcium ≤7.0), meeting lab TLS. However, creatinine is 1.22× baseline (not yet 1.5×), and no arrhythmia or seizure is documented — so clinical TLS criteria are not met. This is lab TLS, which requires immediate escalation of monitoring and management before organ dysfunction develops.