The commonly used continuous intravenous (i.v.) furosemide dosing schedule after cardiac surgery in children is largely empirical and may not be optimal. This may even be more marked in children after cardiac surgery who are haemodynamically unstable, and in whom transient renal insufficiency may occur. A study was performed to obtain an impression regarding which clinically applicable measures may be used to design a rational scheme for continuous i.v. furosemide therapy in children after cardiac surgery.