'Early' and 'late' timing for renal replacement therapy in acute kidney injury after cardiac surgery: a prospective, interventional, controlled, single-centre trial.

Objectives: Acute kidney injury after cardiac surgery (CS-AKI) is strongly associated with in-hospital mortality and morbidity. We aimed to investigate whether 'early' or 'late' initiation of renal replacement therapy (RRT) in patients with CS-AKI is associated with a survival benefit or more favourable outcomes.

Methods: All patients who had undergone cardiac surgery at 'Ospedali Riuniti' of Ancona from July 2011 to February 2013 were prospectively enrolled and divided into two treatment groups: the 'early' approach was used during the first 10 months, and the 'late' approach during the next 10 months. 'Early' RRT was started after 6 h of urine output less than 0.5 ml/kg/h, whereas in the 'late' group, therapy started on the basis of persistent (>12 h) oliguria. A total of 1658 patients were enrolled in the trial. The primary outcome was operative mortality, and the secondary outcomes were length of intensive care unit and hospital stay.

Results: The total number of patients treated with RRT was 59 (3.6%): 46 (5.5%) in the 'early' group and 13 (1.6%) in the 'late' group (P < 0.0001). Although RRT was significantly less utilized in the 'late' group, no significant difference in the primary and secondary outcomes was found, but a trend towards a better outcome in the 'late' group was observed. Furthermore, we found a significant difference in mortality between the two approaches in the subgroups of patients with preoperative renal dysfunction and in patients suffering from CS-AKI with a clear advantage of the late strategy.

Conclusions: Our results do not support the use of early RRT in CS-AKI.

Clinical Trial Registration: This trial is registered in the clinicaltrial.gov registry: NCT01961999.