Acute kidney injury (AKI) is a common complication in critically ill patients. Based on the sensitive KDIGO criteria, the incidence of AKI on ICU varies between 30-60 %. These large variations of incidence of AKI are due to different baseline characteristics of studied patients, the length of observation period, use of creatinine criteria only or use of creatinine and urine output criteria. Furthermore, back estimation of baseline creatinine instead of measured creatinine in patients with missing laboratory values may lead to overestimation of AKI severity and outcomes. Major surgery, trauma, infection, sepsis or a complication of severe illness can lead to an abrupt decrease in glomerular filtration in critically ill patients. Such episode of AKI is associated with short term adverse effects such as fluid overload, electrolyte imbalance, acid-base derangements, immune dysfunction, coagulation abnormalities and alterations in mental status. Additionally, AKI in critically ill patients leads to prolonged ICU length of stay, increase in morbidity and mortality as well as higher costs. Multiple large studies found, after correction for potential confounders, that AKI was independently associated with worse outcomes. Moderate and severe AKI stages were associated with 2.9 - 6.9 fold increased in-hospital mortality (3). Increasing AKI severity in ICU patients was not only associated with increased mortality, AKI patients had also worse renal function at the time of hospital discharge. The individual condition leading to AKI in combination with increased susceptibility to AKI may significantly influence outcome. Indeed, current data from many studies show that mortality from AKI differs in various clinical settings.

However, there are not enough data on different types of surgery and their effect on AKI yet. The aim of our epidemiological study is to investigate the occurrence and outcomes of AKI in different types of surgery in postoperative ICU patients at the Vienna General Hospital.

Inclusion Criteria:

• age > 18 years
• postoperative ICU admission
• preoperative serum creatinine within 2 weeks prior surgery

Exclusion Criteria:

• age < 18 years
• no surgery prior to ICU admission
• renal transplantation prior ICU admission
• chronic renal replacement therapy
• peritoneal dialysis
• missing preoperative serum creatinine within 2 weeks prior surgery

retrospective data analysis of postoperative ICU patients admitted to anaesthesiological and surgical ICUs of the General Hospital Vienna, Austria between January 1, 2016 and December 31, 2018.