What is the likely cause of nausea, vomiting, palpitations, and muscle aches in a patient with Tumor Lysis Syndrome (TLS)?

Hyperkalemia (Answer A)

The most likely cause of nausea, vomiting, palpitations, and muscle aches in this TLS patient is hyperkalemia, which produces this exact symptom constellation and represents an immediately life-threatening emergency requiring urgent ECG monitoring and treatment. 1, 2

Why Hyperkalemia is the Answer

Hyperkalemia produces the precise clinical picture described:

• Cardiac manifestations: Elevated potassium causes arrhythmias, ventricular tachycardia, and fibrillation that manifest as palpitations—the most dangerous acute complication that can cause sudden death 2, 3

• Neuromuscular effects: High potassium levels directly cause muscle cramps and paresthesias, explaining the muscle aches 2

• Gastrointestinal symptoms: Nausea and vomiting occur with hyperkalemia as part of the general TLS presentation, but when combined with palpitations and muscle aches, they specifically point to hyperkalemia 2

Pathophysiology and Mortality Risk

• Rapid tumor cell lysis releases massive amounts of intracellular potassium into the bloodstream, particularly in the 12-72 hour window after chemotherapy initiation 1

• This is further exacerbated by concurrent renal failure, which impairs the kidney's ability to excrete the excess potassium load 1, 2

• Clinical TLS with significant hyperkalemia carries 83% mortality versus 24% in patients without clinical TLS 1

• In Burkitt's lymphoma cohorts, two of four deaths were directly attributable to hyperkalemia 1

Why Not the Other Options

Hypocalcemia (Option B):

• Hypocalcemia typically causes tetany and seizures rather than the symptom pattern described here 1
• Asymptomatic hypocalcemia does not require treatment; only symptomatic cases with tetany and seizures warrant calcium gluconate 4

Hyperuricemia (Option C):

• Hyperuricemia primarily causes acute uric acid nephropathy and renal failure, not the cardiac and neuromuscular symptoms described 4

Hypomagnesemia (Option D):

• Not a characteristic electrolyte abnormality of TLS 5, 6, 7

Immediate Management Required

This patient needs urgent intervention:

• Immediate ECG monitoring for cardiac arrhythmias is mandatory 1

• For severe hyperkalemia (>6 mmol/L):

  • Rapid insulin (0.1 units/kg) plus glucose (25% dextrose 2 mL/kg) to shift potassium intracellularly 4, 2
  • Calcium carbonate 100-200 mg/kg/dose to stabilize myocardial cell membranes and prevent life-threatening arrhythmias 4, 2
  • Sodium bicarbonate to correct acidosis 4
  • Emergency hemodialysis if persistent or life-threatening 4, 2

• For mild hyperkalemia (<6 mmol/L):

  • Aggressive hydration with loop diuretics 4
  • Sodium polystyrene sulfonate 1 g/kg orally or by enema 4

Critical Clinical Pitfall

Hyperkalemia should be treated quickly and aggressively as its presence is the most hazardous acute complication in TLS 3. The combination of palpitations (cardiac) and muscle aches (neuromuscular) demands immediate assessment before progression to cardiac arrest 1.