The Relationship Between Measured Creatinine Clearance and Acute Kidney Injury in Critically Ill Patients

With this study, the investigators want to find out how well different stages of acute kidney injury (AKI), match with the actual filtering ability of the kidneys in very sick adults in the intensive care unit (ICU). Kidney function will be measured using a urine test that estimates how much waste the kidneys can clear from the blood. The investigators will also compare two ways of diagnosing and staging AKI: one based on how much urine a person makes, and the other based on blood creatinine levels (a waste product that rises when kidney function worsens). In addition, the investigators will examine how factors that can be changed (such as treatments or medications) and factors that cannot be changed (such as age or existing health conditions) may affect this relationship. Finally, the investigators will look at whether drops in kidney function are linked to problems like high potassium levels in the blood and a buildup of acid in the body.