A -year-old man with recently diagnosed Burkitt lymphoma is evaluated in the hospital on the second day of his induction chemotherapy regimen. He reports new-onset nausea, generalized weakness, and severe muscle cramps. Over the past hours, his urine output has decreased to approximately mL. His temperature is (), blood pressure is mmHg, pulse is /min, and respirations are /min. Physical examination reveals muscle fasciculations and diffuse weakness. Laboratory studies show the following:
| Laboratory Test | Result |
|---|---|
| Sodium | mEq/L |
| Potassium | mEq/L |
| Chloride | mEq/L |
| Bicarbonate | mEq/L |
| Blood urea nitrogen | mg/dL |
| Creatinine | mg/dL |
| Calcium | mg/dL |
| Phosphorus | mg/dL |
| Uric acid | mg/dL |
An electrocardiogram is obtained and demonstrates peaked T waves, flattened P waves, and a widened QRS complex. Which of the following is the most appropriate initial step in the management of this patient?
- Administration of intravenous calcium gluconateAnswer
- BAdministration of intravenous regular insulin and dextrose
- CAdministration of intravenous rasburicase
- DInitiation of urgent hemodialysis
- EContinuous intravenous infusion of normal saline
Answer
The most appropriate initial step is the administration of intravenous calcium gluconate to stabilize the cardiac membrane.
The correct answer is the administration of intravenous calcium gluconate. This patient is experiencing tumor lysis syndrome (TLS), an oncologic emergency caused by the massive release of intracellular contents following the initiation of cytotoxic chemotherapy, particularly in high-grade tumors like Burkitt lymphoma. TLS is characterized by hyperkalemia, hyperphosphatemia, hyperuricemia, and hypocalcemia, which can lead to acute kidney injury and fatal arrhythmias. The most immediate threat to this patient's life is severe hyperkalemia ( mEq/L) with progressive electrocardiographic (ECG) changes (peaked T waves, flattened P waves, and a widened QRS complex), which can rapidly degenerate into ventricular fibrillation or asystole. The most appropriate initial step in any patient with hyperkalemia and significant ECG changes is to administer intravenous calcium (gluconate or chloride). Calcium does not lower serum potassium levels; rather, it directly antagonizes the membrane actions of hyperkalemia, thereby raising the threshold potential and stabilizing the cardiac myocardium. This effect is almost immediate, buying time to administer definitive potassium-lowering therapies.
Step-by-Step Solution
Key Concept
In patients with tumor lysis syndrome, severe hyperkalemia with electrocardiographic changes is a medical emergency that requires immediate cardiac membrane stabilization with intravenous calcium before administering therapies to lower serum potassium.
Estimated Time:1m 30s