Oliguria, Acute Kidney Injury, and Principles of Blood Purification

Acute kidney injury (AKI), is defined by a rapid increase in serum creatinine, decrease in urine output, or both. Its incidence in intensive care has been reported in more than 50% of patients. In neurocritical patients, non-neurological complications such as AKI are independent predictors of worse clinical outcomes. Different research groups have reported an AKI incidence in neurocritical care patients of 11.6% with an incidence of Kidney Disease: Improving Global Outcomes (KDIGO) stage 3 AKI that requires dialysis ranging from 3% to 12%. Trauma-induced AKI, sepsis, sympathetic overstimulation, tubular epitheliopathy, hyperchloremia, use of nephrotoxic drugs, and renal hypoperfusion are the most common causes of AKI in neurocritical patients. AKI is the result of a sum of events, though the mechanisms underlying many of them remain uncertain. This review will focus on AKI in neurocritical care patients. Specifically, it will be discussed AKI epidemiology, causes, associated mechanisms, and physiological relationship between brain and kidney or physiological brain–kidney connection. Additionally, we will review, the principles, logistics, and risks of extracorporeal therapies for blood purification in this group of patients.