This is a single center, randomized, single-blind, placebo-controlled study to evaluate the safety and biochemical effects of niacinamide on metabolic parameters of the kidney in patients undergoing cardiac surgery.

Inclusion criteria

1. All patients undergoing cardiac surgery with the use of cardiopulmonary bypass at high risk for acute kidney injury. A Cleveland score of 6 or more is used to define patients at high risk for acute kidney injury
2. Age ≥ 18
3. Signed informed consent

Exclusion criteria

1. Pre-existing acute kidney injury
2. Kidney transplantation
3. Off-pump heart surgery
4. Pregnancy
5. End stage renal disease
6. Pregnancy (female subjects of childbearing potential must have a negative serum pregnancy test)
7. Subjects with any kind of dependency on the investigator (e.g. any subject who is under direct supervision of the investigator/co-investigators or employed by the investigator/co-investigators) 8 Subjects held in an institution by legal or official order (e.g. subjects in jail, prison, juvenile offender facility, or treatment facility including those who are in hospitals, alcohol, and drug treatment facilities under court order, and individuals with psychiatric illnesses who have been committed involuntarily to an institution)