The decision when to initiate replacement therapy (RRT) in patients with acute kidney injury (AKI) is extremely variable and tends to be based on empiricism, depending upon the immediate and projected trajectory of the clinical situation, clinician experience and local institutional practices and resources. For example, RRT is typically initiated for oliguria, acidosis and correction of volume overload in the intensive care unit (ICU), whereas in the renal ward azotaemia and hyperkalaemia are more common triggers to initiate RRT.