Children with congenital heart defects often need cardiac surgery with cardiopulmonary bypass (the "heart-lung machine"). Approximately 35 to 50% of these children will have "acute kidney injury," or damage to the kidneys, after the procedure. We currently have few medications to prevent this kidney injury. The hypothesis of this study is that giving aminophylline after heart surgery can decrease the acute kidney injury.

Patients are randomized to receive aminophylline or placebo for 72 hours, in a blinded fashion. Serum theophylline levels monitor for safety of aminophylline dose. Goal theophylline levels is 5-7 mcg/ml. Laboratory results will be faxed directly to the pharmacy who will adjust subsequent aminophylline dosing to maintain appropriate theophylline levels. Urine output and serum creatinine levels will be monitored to assess acute kidney injury. Serum Neutrophil Gelatinase Associated Lipocalin (NGAL) levels will also be monitored.

Inclusion Criteria:

• Less than 18 years old, undergoing cardiac surgery with bypass
• neonates must be at least 36 weeks gestational age

Exclusion Criteria:

• History of arrythmia or seizure, on extracorporeal membrane oxygenation (ECMO) support, already taking aminophylline/theophylline, liver failure, sepsis, on renal replacement therapy

Data were collected over the first five postoperative hospital days.

Systematic Assessment: each patient was evaluated daily for an adverse event.