A nurse is caring for a client admitted for non-Hodgkin's lymphoma and chemotherapy. The client reports nausea, flank pain, and muscle cramps. What action by the nurse is most important.

Choice A rationale Requesting an order for serum electrolytes and uric acid is the most crucial initial action because the client's symptoms (nausea, flank pain, muscle cramps) following chemotherapy for lymphoma are highly suggestive of tumor lysis syndrome (TLS). TLS is an oncologic emergency characterized by the rapid release of intracellular contents, leading to hyperuricemia (uric acid > 6 mg/dL), hyperkalemia (potassium > 5.0 mEq/L), hyperphosphatemia (phosphate > 4.5 mg/dL), and secondary hypocalcemia (calcium < 9.0 mg/dL). These metabolic imbalances require immediate laboratory confirmation for proper management. Choice B rationale Increasing the IV infusion rate may be a component of TLS management to help promote renal excretion of uric acid and electrolytes, but it should not be initiated without first obtaining laboratory results to confirm the diagnosis and severity of the metabolic derangements. Aggressive IV hydration is essential for maintaining a high urinary output and preventing acute kidney injury from uric acid crystal deposition, but it follows the diagnostic confirmation. Choice C rationale Instructing assistive personnel to strain all urine is primarily indicated for clients suspected of having kidney stones (nephrolithiasis), which could present with flank pain. While uric acid nephropathy is a complication of TLS, straining urine is not a key intervention for managing the life-threatening metabolic abnormalities like hyperkalemia or hyperphosphatemia associated with TLS, making Choice A a higher priority. Choice D rationale Administering an IV antiemetic would address the client's symptom of nausea, providing symptomatic relief. However, nausea is a nonspecific symptom in this context. Treating only the nausea does not address the underlying, potentially fatal, metabolic instability caused by tumor lysis syndrome, which must be immediately diagnosed and managed to prevent complications such as cardiac dysrhythmias and acute kidney injury.