Acute Renal Replacement Therapy in Intensive Care Units versus Outside Intensive Care Units: Are They Different?

Introduction: Acute renal replacement therapy (RRT) is indicated when metabolic and fluid demands exceed total kidney capacity, and demand for kidney function is determined by non-renal comorbidities, severity of acute disease and solute and fluid burden; therefore, the criteria for commencing RRT and dialysis in intensive care units (ICUs) may be different to those outside ICUs.

Objective: We investigated whether criteria for commencing acute RRT and dialysis outside ICU were different to those in ICU and whether these differences affected patient mortality in either setting.

Methods: We performed a retrospective observational study evaluating acute kidney injury (AKI), Kidney Disease Improving Global Outcome 3 (KDIGO3) in adult patients undergoing RRT "in and outside" ICU from 2012 to 2018, in a Brazilian teaching hospital.

Results: We evaluated 913 adults with AKI KDIGO3 undergoing RRT; 629 (68.9%) outside ICU and 284 (31.1%) in ICU. Infections were the main cause of hospitalisation (34.4%). Septic and ischaemic AKI were the main aetiologies of AKI (50.8% and 32.9%, respectively), metabolic and fluid demand to capacity imbalance were the main indications for dialysis (69.7%), and intermittent haemodialysis (IHD) was the primary dialysis method (59.2%). The general mortality rate after 30 days was 59%. There were no differences in gender, age and main diagnosis between groups. Both groups were different in acute tubular necrosis index specific scores (ATN-ISS), AKI aetiology, elderly population, indications for dialysis, dialysis methods and mortality rates. In ICU, patients older than 65 years old, with septic AKI were more prevalent (49.1 versus 41.4%, and 55.1 versus 37.5%, respectively), while ischaemic and nephrotoxic AKI were less frequent (24.3 versus 37 and 10.2 versus 16.3%, respectively), and ATN-ISS was higher (0.74 ± 0.31 versus 0.58 ± 0.16). Similarly, metabolic and fluid demand to capacity imbalance as an indication for acute RRT, prolonged intermittent haemodialysis (PIRRT) and continuous renal replacement therapy (CRRT) were more frequent, while peritoneal dialysis (PD) was less frequent (74.6 versus 69.7%, 31.6 versus 22.4%, and 5.3 versus 17.8%, respectively), and mortality was higher (69 versus 54.7%, respectively). Logistic regression revealed that age, septic AKI and being "in" ICU were factors associated with death.

Conclusion: The criteria for commencing RRT and dialysis in ICU were different to those outside ICU; however, they did not impact on patient outcomes.