Objective:To determine if inclusion of urine output (UO) into the definition of acute renal failure (ARF) increases its incidence in long-term ICU patients. Design: Retrospective analysis of patients medical records. Setting: Department of Anaesthesiology and Intensive Care, St. Anna’s University Hospital, Brno, Czech Republic. Material and Methods: Analysis of medical records of long-term (> 3 days) ICU patients hospitalised in 2000. Urine output, urea and creatinine during ICU stay were reviewed every day, and ARF diagnosed according to criteria recently proposed [1]. Furosemide administration was also recorded. Values are given as means ± SD (range). Results: 90 out of 189 patients hospitalised in 2000 stayed in the ICU more than 3 days. Eighty four medical records were available for analysis – mean age 59 (16–85 years), APACHE II on admission 25.4 ± 7.7. Altogether 1196 ICU days were analysed. Seven patients required renal replacement therapies for 39 days (i.e. severe acute renal failure syndrome – ARFS). Out of remaining 1157 ICU days, the complete data set (i.e.UO,urea,creatinine)wasavailable in 340 cases because creatinine was not performed on daily basis. Renal metabolite levels led to ARF diagnosis in 62 ICU days (18.2%). Inclusion of UO increased the number of ARF ICU days by 14 (altogether 22.4%). In 2 ICU days more severe degree of ARF was diagnosed according to UO compared to metabolites criteria. In all but 1 patient low UO was present when no furosemide was given. When all 1157 ICU days were analysed according to UO and urea levels, UO-based ARF was found in 97 ICU days (8.4%). In 40 of these cases patients had normal urea level. When urea was the only parameter used for ARF diagnosis, 550 ICU days (47.5%) classified as ARF ICU days. Conclusion: In long term ICU patients who are not given furosemide inclusion of low urine output into ARF definition leads to increase of its incidence.

        Key words: acute renal failure – urine output – intensive care