Hyperkalemia is the Most Likely Cause
In a patient with Tumor Lysis Syndrome (TLS) presenting with nausea, vomiting, palpitations, and muscle aches, hyperkalemia is the most likely culprit and represents the most immediately life-threatening electrolyte abnormality requiring urgent evaluation and treatment. 1
Why Hyperkalemia is the Primary Concern
Hyperkalemia produces the exact symptom constellation described:
- Cardiac manifestations: Palpitations result from cardiac irregularities including arrhythmias, ventricular tachycardia, and potentially cardiac arrest 1, 2
- Neuromuscular effects: Muscle aches, cramps, and paresthesias are direct consequences of elevated potassium levels 1, 3
- Gastrointestinal symptoms: Nausea and vomiting are common clinical manifestations of TLS-related hyperkalemia 1
The rapid release of intracellular potassium from lysed tumor cells leads to hyperkalemia, which may be further exacerbated by concurrent renal failure 1. This represents the most hazardous acute complication of TLS and can cause sudden death from cardiac arrhythmias 4.
Why Not the Other Options
Hypocalcemia
While hypocalcemia does occur in TLS due to calcium-phosphate precipitation, it typically causes tetany and seizures rather than the symptom pattern described 1. Asymptomatic hypocalcemia does not require treatment 1. The palpitations and muscle aches in this scenario are more consistent with hyperkalemia's cardiac and neuromuscular effects.
Hyperuricemia
Hyperuricemia primarily causes renal complications through uric acid crystal deposition in renal tubules, leading to acute kidney injury 1, 5. While it contributes to the overall TLS picture, it does not directly produce palpitations, nausea, or muscle aches as presenting symptoms 6.
Hypomagnesemia
This is not a characteristic feature of TLS. The classic electrolyte abnormalities in TLS are hyperkalemia, hyperphosphatemia, hypocalcemia, and hyperuricemia 4, 7, 8. Hypomagnesemia is not part of the TLS metabolic derangement pattern.
Clinical Management Priority
Hyperkalemia should be treated quickly and aggressively as it is the most immediately dangerous complication 4. Treatment includes:
- Immediate ECG monitoring for cardiac arrhythmias 1
- For severe hyperkalemia: rapid insulin (0.1 units/kg) plus glucose (25% dextrose 2 mL/kg), calcium carbonate 100-200 mg/kg/dose to stabilize myocardial membranes, and sodium bicarbonate to correct acidosis 1
- For mild hyperkalemia (<6 mmol/L): hydration, loop diuretics, and sodium polystyrene 1 g/kg 1
The combination of palpitations (cardiac effects) and muscle aches (neuromuscular effects) with gastrointestinal symptoms in a TLS patient creates a clinical picture that demands immediate assessment and treatment of hyperkalemia before it progresses to life-threatening arrhythmias or cardiac arrest 1, 2.