Acute kidney injury (AKI) is a frequent and important complication of cardiac surgery. Decreased perfusion is a key mechanism. This decreased perfusion may be attenuated by intravenous amino acids (AAs) through recruitment of renal functional reserve.

The study investigators performed a PubMed search of all articles published from 1980 to August 30, 2024, with combined search criteria of “renal functional reserve,” “amino acids,” “cardiac surgery,” and “cardiopulmonary bypass” by using MEDLINE (PubMed), Embase, and the Cochrane Central Register of Clinical Trials. Included were studies describing the effect of AAs on renal functional reserve and studies of adult cardiac surgery patients with information on renal function. A narrative review was developed.

Multiple experimental and human studies over >40 years have recurrently and consistently shown that the administration of an oral protein load or intravenous AAs increase renal blood flow and glomerular filtration rate by >30%. Moreover, several pilot investigations in cardiac surgery with cardiopulmonary bypass consistently showed renal benefits with intravenous AAs. Finally, a pivotal trial of 3511 cardiac surgery patients (the PROTECTION trial) recently confirmed such beneficial effects in a double-blind multicenter international setting.

Intravenous AAs consistently recruit renal functional reserve and improve kidney function in cardiac surgery patients. These findings have been confirmed by the PROTECTION (Intravenous Amino Acid Therapy for Kidney Protection in Cardiac Surgery) trial. Intravenous AA therapy is the only proven treatment to prevent and/or attenuate the severity of cardiac surgery−associated AKI.