PEEP-induced Changed in RRI as Physiological Background of Ventilator-induced Kidney Injury

The renal Doppler resistive index (RRI) is a noninvasive tool that has been used to assess renal perfusion in the intensive care unit (ICU) setting. Many parameters have been described as influential on the values of renal RI. Mechanical ventilation is associated with significant increases in the risk of acute kidney injury (AKI). Ventilator-induced kidney injury (VIKI) is believed to occur due to changes in hemodynamics that impair renal perfusion. The investigators hypothesized that patients who need mechanical ventilation should have a different response in RRI when different levels of Positive end expiratory pressure (PEEP) are applied. Investigators wish to describe changing in RRI due to changes in PEEP and to verify whether these changes could partially explain the occurrence of VIKI