Correlation between parameters at initiation of renal replacement therapy and outcome in patients with acute kidney injury

INTRODUCTION Renal replacement therapy (RRT) is a fully established treatment for critically ill patients with acute kidney injury (AKI) but there are no scientifically established criteria when to initiate it. Our objectives were to describe the epidemiology of critically ill patients with AKI receiving RRT and to evaluate the relationship between biochemical, physiological and comorbid factors at time of RRT and ICU mortality. METHODS Retrospective analysis of demographic and physiologic data of 1,847 patients who received RRT for AKI in 22 ICUs in UK and Germany between 1989 - 1999. RESULTS 54.1% of RRT patients died in ICU. ICU survivors were younger, had a lower APACHE II score and fewer failed organ systems on admission to ICU compared to non-survivors. Multivariate analysis showed that at time of initiation of RRT, independent risk factors for ICU mortality were mechanical ventilation [odds ratio (OR) 6.03], neurological failure (OR 2.48), liver failure (OR 2.44), gastrointestinal failure (OR 2.04), pre-existing chronic illnesses (OR 1.74), haematological failure (OR 1.74), respiratory failure (OR 1.62), oligoanuria (OR 1.6), age (OR 1.03), serum urea (OR 1.004) and cardiovascular failure (OR 1.3). A higher pH at initiation of RRT was independently associated with a better outcome. Failure to correct acidosis and development of more organ failure within 48 hours after initiation of RRT were also associated with an increased risk of dying in ICU. CONCLUSIONS Oligoanuria, acidosis and concomitant dysfunction of other organs at time of RRT were associated with poor survival. In contrast, serum creatinine and urea levels only had a weak correlation with outcome after RRT.