A RIFLE score-based trigger for renal replacement therapy and survival after cardiac surgery

Introduction

It is controversial whether all critically ill patients with RIFLE-F class acute kidney injury (AKI) should receive renal replacement therapy (RRT). We reviewed the outcome of open-heart surgery patients with severe AKI who did not receive RRT.

Methods

We identified all patients who developed AKI after cardiac surgery during a 4-year period, and obtained baseline characteristics, intraoperative details and in-hospital outcomes. We analyzed physiological and biochemical features at the time of RRT initiation or at peak creatinine if no RRT was provided.

Results

We reviewed 1,504 patients. Of these, 137 (9.1%) developed postoperative AKI with 71 meeting RIFLE-F criteria and 23 (32.4% of RIFLE-F cases) not receiving RRT. Compared with RRT-treated RIFLE-F patients, no-RRT patients had lower APACHE III scores, less intraaortic balloon pump requirements, shorter intensive care stay and a trend toward lower mortality. At peak creatinine, their urinary output, arterial pH and PaO₂/FIO₂ ratio were all significantly higher. Their serum creatinine was also higher (304 vs. 262 μmol/l, P = 0.02). Only three died in-hospital. Detailed review of cause and mode of death was consistent with non-RRT-preventable deaths. In contrast, 27 patients with RIFLE-R or RIFLE-I class received RRT. Compared with RRT-treated RIFLE-F patients, they had a trend towards a more severe presentation and a higher mortality (51.8% vs. 29.2%, P = 0.02). See Figure 1.

Figure 1

Flow chart. ASCTS, Australian Society of Cardio Thoracic Sugery.

Conclusion

After cardiac surgery, RRT is typically applied to patients with the most severe clinical presentation irrespective of creatinine levels. A RIFLE score-based trigger for RRT is unlikely to improve patient survival.