Septic acute kidney injury: new concepts

Abstract

Acute kidney injury (AKI) is a serious condition that affects many ICU patients. The most common causes of AKI in ICU are severe sepsis and septic shock. The mortality of AKI in septic critically ill patients remains high despite of our increasing ability to support vital organs. This is partly due to our poor understanding of the pathogenesis of sepsis-induced renal dysfunction. However, new concepts are emerging to explain the pathogenesis of septic AKI, which challenge previously held dogma. Throughout the past half century, septic AKI has essentially been considered secondary to kidney ischemia. However, recent models of experimental sepsis have challenged this notion by demonstrating that, in experimental states, which simulate the hemodynamic picture most typically seen in man (e.g. hyperdynamic sepsis) renal blood flow, actually increases as renal vascular resistance decreases. These experimental observations provide proof of concept that septic AKI can occur in the setting of renal hyperemia and that ischemia is not necessary for loss of glomerular filtration rate (GFR) to occur. They also suggest that similar hemodynamic event may occur in man. In addition, preliminary studies in septic sheep show that, when ATP is measured using an implanted phosphorus coil and magnetic resonance technology, renal bioenergetics are preserved in the setting of advanced septic shock. While these findings need to be confirmed, they challenge established paradigms and offer a new conceptual framework of reference for further investigation and intervention in man.