Acute kidney injury after cardiac surgery: Sustained low efficiency compared to continuous renal replacement therapy

Abstract

Study objective: Sustained low efficiency dialysis (SLED) has been introduced as a mode of renal replacement therapy (RRT) for treating severe cardiac surgery-associated acute kidney injury (CSA-AKI) at some hospitals; SLED is performed using intermittent hemodialysis (IHD) devices but differs from conventional IHD in its duration and intensity. However, there are limited data comparing SLED against more conventional continuous RRT methods. We conducted a retrospective cohort study to compare outcomes of patients with severe CSA-AKI after an institutional transition from continuous RRT to SLED.

Design: Following research ethics approval, we conducted a retrospective cohort study of patients with severe CSA-AKI requiring RRT.

Setting: Cardiac Intensive Care Unit at the Toronto General Hospital (Toronto, Ontario, Canada) from 1 January 1999 to 31 December 2011.

Patients: 351 consecutive patients with severe CSA-AKI requiring RRT after cardiac surgery.

Interventions: The RRT mode was continuous RRT before 31 March 2008, and SLED after 1 April 2008.

Measurements: The primary outcome was low-cardiac output syndrome (LCOS) and the main secondary outcome was associated costs. Propensity score matched-pairs analyses were used to compare the outcomes of patients in the continuous RRT period versus the SLED period.

Main results: There were 268 patients treated with continuous RRT and 83 patients treated with SLED. The SLED group had a higher weight, higher baseline hemoglobin concentration, and higher prevalence of obstructive lung disease. In propensity score match-pairs analysis (n = 148), the SLED group experienced similar odds of low cardiac output syndrome (odds ratio [OR] 1.06, 95% CI 0.68 to 1.67), death (OR 1.09, 0.94 to 1.28), acute stroke (OR 0.97, 0.83 to 1.13), myocardial infarction (OR 0.92, 0.84 to 1.01). The use of SLED was associated with a reduced cost compared to continuous RRT. The cost differential for 83 treated patients was CAD$130,974 (CAD$178,159.50 vs CAD$309,133.50) in favor of SLED.

Conclusions: An institutional transition from continuous RRT to SLED, was associated with a significant lower cost with the use of SLED, while maintaining comparable postoperative outcomes in CSA-AKI patients.

Keywords: Acute kidney injury; Cardiac surgery; Continuous renal replacement therapy; Sustained-low efficiency dialysis.