A 48-year-old man is hospitalized for the initiation of induction chemotherapy for recentl… — USMLE Step 2 CK

A 48-year-old man is hospitalized for the initiation of induction chemotherapy for recently diagnosed Burkitt lymphoma. Twenty-four hours after starting the multi-agent regimen, he develops diffuse muscle cramps, generalized weakness, and nausea. His temperature is $37.2^\circ\text{C}$ ( $99.0^\circ\text{F}$ ), blood pressure is $115/75\text{ mmHg}$ , pulse is $112/\text{min}$ , and respirations are $18/\text{min}$ . Physical examination reveals hyperactive deep tendon reflexes and occasional muscle twitching. Laboratory results are as follows:

* Sodium: $138\text{ mEq/L}$
* Potassium: $7.1\text{ mEq/L}$
* Bicarbonate: $18\text{ mEq/L}$
* Blood urea nitrogen (BUN): $48\text{ mg/dL}$
* Creatinine: $3.2\text{ mg/dL}$ (Baseline: $0.9\text{ mg/dL}$ )
* Calcium: $6.2\text{ mg/dL}$
* Phosphorus: $9.0\text{ mg/dL}$
* Uric acid: $15.5\text{ mg/dL}$

An electrocardiogram reveals peaked T waves and a shortened QT interval. Which of the following is the most appropriate immediate next step in management?

Administer intravenous calcium gluconateAnswer
B
Administer intravenous rasburicase
C
Administer intravenous sodium bicarbonate
D
Administer regular insulin and dextrose
E
Initiate urgent hemodialysis

Answer

Administer intravenous calcium gluconate

This patient presents with classic features of tumor lysis syndrome (TLS) following chemotherapy for Burkitt lymphoma. The rapid lysis of tumor cells releases massive amounts of intracellular contents, leading to hyperkalemia, hyperphosphatemia, and hyperuricemia. The hyperphosphatemia subsequently binds serum calcium, causing hypocalcemia. The most immediate life-threatening derangement in this scenario is severe hyperkalemia (

7.1\text{ mEq/L}

) accompanied by characteristic ECG changes (peaked T waves). The first and most critical step in managing hyperkalemia with ECG changes is cardiac membrane stabilization using intravenous calcium (e.g., calcium gluconate). This prevents fatal arrhythmias while other measures (like insulin/dextrose or hemodialysis) are prepared to definitively lower the total body serum potassium.

Step-by-Step Solution

Identify the primary diagnosis based on the clinical context and laboratory data.

The patient has Tumor Lysis Syndrome (TLS) characterized by hyperkalemia, hyperuricemia, hyperphosphatemia, and secondary hypocalcemia with acute kidney injury.

Initiation of chemotherapy for a rapidly proliferating tumor (Burkitt lymphoma) causes massive cell destruction and release of intracellular contents.

Recognize the most immediate life-threatening complication among the abnormal results.

The patient has severe hyperkalemia (

7.1\text{ mEq/L}

) with corresponding electrocardiographic changes (peaked T waves).

Severe hyperkalemia with ECG changes indicates an imminent high risk for fatal ventricular arrhythmias and cardiac arrest.

Determine the optimal first step in pharmacological management.

Intravenous calcium gluconate must be administered immediately.

Calcium directly antagonizes the membrane actions of hyperkalemia and stabilizes the cardiac myocyte membrane, securing the patient's airway and circulation while waiting for definitive potassium-lowering therapies.

Key Concept

The immediate priority in tumor lysis syndrome complicated by severe hyperkalemia and electrocardiographic changes is cardiac membrane stabilization with intravenous calcium.

Question

Answer

Step-by-Step Solution

Key Concept

Common Mistakes

Topics

More questions from this topic