This clinical trial focuses on children with cancer who face infections after receiving chemotherapy. Chemotherapy affects the bone marrow, leading to a decrease in the production of certain white blood cells, particularly those that defend against bacterial infections (neutrophils). One significant concern is febrile neutropenia, where children experience a fever during a period of low white blood cell count. This condition often results from bacterial infections, necessitating prompt wide-spectrum antibiotic treatment. However, some children eliminate antibiotics in the urine too quickly during febrile neutropenia. Their kidneys function more than they normally do (renal hyperfiltration). This can lead to insufficient exposure to antibiotics to control the infection. The current standard antibiotic regimens do not account for this variable elimination rate. In this study we focus on two antibiotics used in this context: piperacillin-tazobactam and meropenem. The main questions this study aims to answer are, in these children: * Would higher doses of antibiotics result in better blood levels of antibiotics? * Would they have more sides effects with higher antibiotics dosages? * Would they recover more quickly with higher antibiotic doses? All patients will undergo a blood test upon hospital arrival, including an assessment of renal function. If renal function is normal or diminished, the patient will receive the standard antibiotic dose. Children with increased renal function will be randomly assigned to two groups during each episode of febrile neutropenia. One group will receive standard antibiotic dosages, while the other will receive higher doses to compensate for renal hyperfiltration. Throughout the study, antibiotic levels in the blood will be monitored for all patients. This monitoring will determine if target concentrations can be achieved more quickly with experimental dosages and will allow doctors to readjust the doses if needed.