In a patient with tumor lysis syndrome presenting with nausea, palpitations, and muscle weakness, which electrolyte abnormality is most likely responsible?

Hyperkalemia is Causing These Symptoms

In a patient with tumor lysis syndrome presenting with nausea, palpitations, and muscle weakness, hyperkalemia is the electrolyte abnormality most directly responsible for this specific symptom triad. This combination demands immediate recognition and treatment before progression to life-threatening arrhythmias or cardiac arrest. 1

Why Hyperkalemia Explains This Clinical Picture

The rapid lysis of tumor cells releases massive amounts of intracellular potassium into the bloodstream, which is further exacerbated by concurrent renal failure that impairs potassium excretion. 2, 3 This pathophysiologic mechanism directly produces the patient's symptoms:

• Palpitations result from cardiac irregularities including arrhythmias, ventricular tachycardia, and fibrillation caused by elevated potassium levels 2, 3
• Muscle weakness and cramps are neuromuscular manifestations of high potassium levels 2, 3
• Nausea is part of the general clinical manifestations of TLS, but when combined with palpitations and muscle weakness, specifically points to hyperkalemia 3

Why Other Options Are Less Likely

While hypocalcemia, hyperuricemia, and hypomagnesemia can all occur in TLS, they do not produce this specific symptom constellation:

• Hypocalcemia typically causes tetany and seizures rather than palpitations and muscle weakness 2, 1
• Hyperuricemia primarily causes renal complications through crystal deposition, leading to oliguria and acute renal failure, not the cardiac and neuromuscular symptoms described 2, 4
• Hypomagnesemia is not a cardinal feature of TLS 2, 4

Critical Clinical Context

Clinical TLS with significant hyperkalemia carries an 83% mortality rate compared to 24% in patients without clinical TLS. 3 In a Burkitt's lymphoma cohort, two of four deaths were directly attributable to hyperkalemia, underscoring its life-threatening nature. 1, 3

Hyperkalemia can progress rapidly from mild symptoms (muscle cramps, palpitations) to life-threatening arrhythmias and sudden cardiac death. 4 This patient requires:

• Immediate ECG monitoring for cardiac arrhythmias 1
• Urgent potassium level measurement 4
• For severe hyperkalemia (≥6 mmol/L): rapid insulin (0.1 units/kg) plus glucose (25% dextrose 2 mL/kg) to shift potassium intracellularly, calcium carbonate (100-200 mg/kg/dose) to stabilize myocardial membranes, and continuous ECG monitoring 2, 4, 3
• Emergency hemodialysis if hyperkalemia is persistent or life-threatening and unresponsive to medical management 4, 3

Answer: A - Hyperkalemia