he tumor lysis syndrome is the most common disease-related emergency encountered by physicians caring for children or adults with hematologic cancers. Although it develops most often in patients with non-Hodgkin's lymphoma or acute leukemia, its frequency is increasing among patients who have tumors that used to be only rarely associated with this complication. The tumor lysis syndrome occurs when tumor cells release their contents into the bloodstream, either spontaneously or in response to therapy, leading to the characteristic findings of hyperuricemia, hyperkalemia, hyperphosphatemia, and hypocalcemia. These electrolyte and metabolic disturbances can progress to clinical toxic effects, including renal insufficiency, cardiac arrhythmias, seizures, and death due to multiorgan failure.Although optimal methods of risk classification and treatment have been difficult to define, uniform standards for management of the tumor lysis syndrome are beginning to evolve. Indeed, several groups have advocated guidelines for risk stratification and made recommendations for evaluating risk and for prophylactic therapy for the tumor lysis syndrome. This review of the tumor lysis syndrome summarizes current strategies for risk assessment, prophylaxis, and therapy. The following case illustrates the clinical challenges.
C a se r eport
An 8-year-old boy was referred to an otolaryngologist for tonsillectomy after several months of increased snoring, fatigue, sore throat, enlarged tonsils, and gradually increasing painless and nontender cervical lymphadenopathy. Two days before the scheduled procedure, his parents took him to the local emergency department after he had been unable to sleep because of congestion, sore throat, and difficulty breathing. The physician in the emergency department documented nasal congestion, enlarged tonsils that touched in the midline, and significant anterior and posterior cervical adenopathy. Dexamethasone (4 mg) was administered intramuscularly, and loratadine was prescribed. During the next 36 hours, the patient's congestion and breathing improved somewhat, but malaise developed and he vomited repeatedly. He returned to the emergency department, where he appeared ill and was found to be moderately dehydrated. Evaluation showed a white-cell count of 84,600 per cubic millimeter, with circulating lymphoblasts; a sodium level of 133 mmol per liter; potassium, 5.9 mmol per liter; bicarbonate, 16 mmol per liter; creatinine, 1.0 mg per deciliter (88.4 ฮผmol per liter); phosphorus, 8.5 mg per deciliter (2.7 mmol per liter); calcium, 6.7 mg per deciliter (1.7 mmol per liter); uric acid, 12.3 mg per deciliter (732 ฮผmol per liter); and lactate dehydrogenase, 4233 IU per liter. Chest radiography revealed a small mediastinal mass, and an electrocardiogram was normal. The pa-