This patient with ALL is at high risk for tumor lysis syndrome following his initial chemotherapy treatment. Tumor lysis syndrome is characterized by hypercalcemia, hyperuricemia, and acute renal failure and is particularly common in patients with leukemia and high-grade lymphoma. Moreover, this patient presents with risk factors for severe tumor lysis syndrome, namely WBC > 100,000/ul and LDH three times the upper limit of normal. In high risk patients, it is recommended to start aggressive high-volume intravenous fluids 24-48 hours before the first chemotherapy session to protect against acute renal failure. Routine observation is not appropriate for this high-risk patient because his clinical condition can rapidly deteriorate. Three-hour checks on labs and renal function is an appropriate level of monitoring for this patient, but pretreatment intravenous fluid therapy is a more appropriate next step. Hemodialysis is indicated only in patients with tumor lysis syndrome who develop severe acute renal failure or severe refractory electrolyte imbalances.