12 hours after induction chemotherapy for acute leukemia, which finding requires the nurse's immediate action?

Rapid tumor breakdown can release intracellular potassium and cause lethal dysrhythmias. Potassium 6.2 mEq/L with peaked T waves is an active cardiac emergency requiring immediate notification, monitoring, and prescribed treatment.

Quick answer
Treat hyperkalemia with electrocardiographic changes as the immediate tumor lysis emergency.

Why this is correct
Induction therapy can destroy many malignant cells at once, releasing potassium, phosphate, and nucleic acids. Peaked T waves show that the elevated potassium is already affecting cardiac conduction, so stabilization cannot wait for routine follow-up.

Easy analogy or mental picture
Tumor lysis is like many storage cells breaking open at once and flooding the electrical system. The analogy highlights the sudden electrolyte load but does not replace measurement of potassium, phosphate, calcium, uric acid, and kidney function.

Memory hook
After chemotherapy, high potassium plus ECG change means act now.

NCLEX decision rule
Prioritize a laboratory abnormality when it is paired with present organ dysfunction. In suspected tumor lysis syndrome, dysrhythmia risk outranks stable anemia, noncritical thrombocytopenia, or leukopenia without fever.

Why the other choices are wrong
The anemia and thrombocytopenia need follow-up but show no immediate instability. Leukopenia raises infection risk, yet the listed temperature does not indicate fever.