Nursing care
Tumour Lysis Syndrome nursing care: what to assess and what to do first
Written and reviewed by Dana Whitfield, RN, MSN · 5 min read · Updated September 2026
Short answer
Tumour lysis syndrome is the rapid release of intracellular contents after chemotherapy destroys a large number of malignant cells, causing high potassium, phosphate and uric acid alongside low calcium. It typically appears within 12 to 72 hours of treatment starting. Aggressive IV hydration and allopurinol or rasburicase before and during chemotherapy are the standard prevention.
Recognising it at the bedside
Watch for the cluster rather than any single symptom: muscle cramps or weakness from hyperkalaemia, nausea and lethargy from rising uric acid, and tetany or a positive Chvostek's sign from the calcium drop that accompanies high phosphate binding calcium in the blood. Decreasing urine output is one of the earliest and most useful bedside findings, since uric acid crystals precipitating in the renal tubules are what drives the kidney injury that follows.
The window to watch is 12 to 72 hours after chemotherapy begins, and risk is highest with bulky, rapidly dividing tumours such as high-grade lymphomas and leukaemias, particularly Burkitt lymphoma and acute lymphoblastic leukaemia. A patient starting induction chemotherapy for one of these should be on continuous cardiac monitoring and hourly urine output tracking from the first dose, not after symptoms appear.
Why the classic presentation misleads
The early symptoms are nonspecific and easy to attribute to the chemotherapy itself. Nausea, fatigue and muscle cramps are also standard chemotherapy side effects, so a nurse unfamiliar with the patient's risk profile can reasonably write them off as expected rather than as the first sign of a metabolic emergency. The diagnosis is frequently made on laboratory criteria before it is made on clinical grounds.
The cardiac risk is also easy to underestimate because hyperkalaemia can cause a fatal arrhythmia before the patient reports feeling unwell. A patient who looks stable on the ward can have a potassium high enough to produce peaked T waves or a widened QRS on the monitor. Treat any new ECG change in a high-risk patient as urgent regardless of how the patient otherwise presents.
Priority nursing actions
Confirm aggressive IV hydration is running before the first chemotherapy dose in any high-risk patient, typically without added potassium or calcium in the fluids, and maintain a urine output target of at least 80 to 100 mL/hour. Insert a urinary catheter for accurate hourly measurement if output cannot be reliably tracked otherwise, and escalate promptly if output falls below target.
Confirm allopurinol or rasburicase has been given as ordered, usually starting one to two days before chemotherapy in anticipated high-risk cases. Place the patient on continuous cardiac monitoring and review the most recent potassium, phosphate, calcium and uric acid results before each chemotherapy dose, not just once daily. If hyperkalaemia is confirmed, anticipate insulin with dextrose, calcium gluconate for cardiac membrane stabilisation if ECG changes are present, and possible dialysis referral for refractory cases. Avoid potassium-containing foods and IV additives entirely during the risk window.
Labs and diagnostics to expect
A basic metabolic panel including potassium, phosphate, calcium and creatinine is drawn at baseline and then repeated every 4 to 6 hours during the acute risk period, tightening or loosening depending on how abnormal the values are. Uric acid is trended alongside these and is the value that allopurinol and rasburicase are specifically targeting.
A 12-lead ECG is obtained at baseline in high-risk patients and repeated with any new symptom or lab abnormality, since it is often the fastest way to catch dangerous hyperkalaemia before the next blood draw comes back. Renal function is tracked closely through creatinine and urine output, as acute kidney injury from uric acid and calcium phosphate crystal deposition is the complication all of this monitoring exists to prevent.
Complications and their early signs
Acute kidney injury is the complication most nurses need to anticipate, driven by uric acid and calcium phosphate crystals obstructing the renal tubules. Falling urine output, rising creatinine, and oedema are the early markers, and they can progress quickly once they start, so a downward trend in output is a reason to act rather than observe.
Cardiac arrhythmia from hyperkalaemia is the most immediately dangerous complication and can occur with little warning. Peaked T waves, a widened QRS, or new ventricular ectopy on the monitor should trigger an immediate potassium check and physician notification regardless of the time since the last scheduled lab. Hypocalcaemic tetany, muscle twitching, or seizures from low calcium are less immediately life-threatening but still warrant prompt correction, since untreated hypocalcaemia can itself provoke arrhythmia.
Teaching that changes outcomes
Explain to the patient before treatment starts why hydration and allopurinol are being given even though they are not the chemotherapy itself, since patients who understand the purpose are more likely to report symptoms early rather than dismissing them as routine side effects. Tell them specifically to report muscle cramping, tingling around the mouth or fingers, or a marked drop in how much they are urinating.
Reinforce that this risk window is time-limited, usually the first few days after a chemotherapy dose, so patients know when heightened vigilance matters most and when it can reasonably ease. Encourage them to keep a rough log of fluid intake and urine output if they are managing any part of care at home, and make sure they know who to call and how urgently if output drops or cramping develops overnight.
The next step on this is the same as on everything else here: answer questions and read the rationales. Our med-surg practice questions are the closest set to what this page covers.
One question from the med-surg set
A client with chronic obstructive pulmonary disease has an oxygen saturation of 88% on 2 L/min via nasal cannula and is alert with no distress. What should the nurse do first?
Rationale
In COPD a saturation of 88–92% is the therapeutic target, not an emergency, and this client is alert with no distress. The first action is the independent nursing intervention that is least invasive and most likely to help: sit them up and reassess. Turning the oxygen up to 6 L/min risks blunting the hypoxic drive, and calling rapid response or drawing an ABG escalates ahead of an assessment you have not finished.
Answer: B
Common questions
Which chemotherapy patients are highest risk for tumour lysis syndrome?
Patients with bulky, fast-growing haematologic malignancies carry the highest risk, particularly Burkitt lymphoma, acute lymphoblastic leukaemia, and other high-grade lymphomas with a large tumour burden. Pre-existing renal impairment or dehydration at the start of treatment raises risk further.
What is the difference between allopurinol and rasburicase in prevention?
Allopurinol blocks new uric acid formation and is used for low-to-intermediate risk patients, typically started a day or two before chemotherapy. Rasburicase breaks down uric acid that is already present and acts faster, so it is reserved for higher-risk patients, and it is contraindicated in G6PD deficiency.
Why is calcium usually withheld from IV fluids in tumour lysis syndrome?
Calcium can combine with the already elevated phosphate to form calcium phosphate crystals that deposit in the kidneys and worsen renal injury. Calcium is only given when the patient has symptomatic hypocalcaemia or ECG changes from hyperkalaemia, and then only as a targeted, short-acting dose.
How soon after chemotherapy does tumour lysis syndrome usually appear?
Most cases develop within 12 to 72 hours of the first chemotherapy dose, which is why monitoring intensifies rather than relaxes in that early window. Some cases can occur even before treatment in very high-burden tumours that are lysing spontaneously.
What NCLEX priority does tumour lysis syndrome usually test?
Questions typically test recognising the electrolyte pattern of high potassium, high phosphate, high uric acid and low calcium together, and then prioritising cardiac monitoring and hydration over less urgent interventions. Expect the correct answer to involve checking the ECG or potassium level before anything else when a high-risk patient reports muscle cramping.
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