Renal Medullary Hypoxia: A New Therapeutic Target for Septic Acute Kidney Injury?

Renal tissue hypoxia has been implicated as a critical mediatory factor in multiple forms of acute kidney injury (AKI), including in sepsis. In sepsis, whole-kidney measures of macrocirculatory flow and oxygen delivery appear to be poor predictors of microcirculatory abnormalities. Studies in experimental hyperdynamic septic AKI have shown that the renal medulla is particularly susceptible to hypoxia early in sepsis, even in the presence of increased global renal blood flow and oxygen delivery. It has been proposed that an early onset of progressive renal medullary hypoxia, leading to oxidative stress and inflammation, can initiate a downward spiral of cellular injury culminating in AKI. Recent experimental studies have shown that clinical therapies for septic AKI, including, fluids, vasopressors, and diuretics, have distinct effects on renal macrocirculation and microcirculation. Herein, we review the clinical and experimental evidence of alterations in global and regional kidney perfusion and oxygenation during septic AKI and associated therapies. We justify the need for investigation of the effects of therapies on renal microcirculatory perfusion and oxygenation. We propose that interventions that do not worsen the underlying renal pathophysiologic and reparative processes in sepsis will reduce the development and/or progression of AKI more effectively.