Fluid Overload and Mortality in Patients with Severe Acute Kidney Injury and Extracorporeal Membrane Oxygenation

Volume overload is increasingly being understood as an independent risk factor for increased mortality in the setting of AKI and critical illness, but little is known about its effect in the setting of extracorporeal membrane oxygenation (ECMO). We sought to evaluate the incidence of AKI and volume overload and their effect on all-cause mortality in adults after ECMO cannulation.

We identified all adult patients who underwent ECMO cannulation at the University of Chicago between January 2015 and March 2017. We evaluated the incidence of KDIGO-defined AKI, RRT, and volume overload. Volume overload was defined as achieving a positive fluid balance of 10% above admission weight over the first 72 hours after ECMO cannulation. The primary outcome collected was 90 day all-cause mortality. Secondary outcomes included 30-day mortality, duration of ECMO and RRT therapy, length of stay, and dialysis independence at 90 days.

There were 98 eligible patients, 83 of whom developed AKI (85%); 48 (49%) required RRT and 19 (19%) developed volume overload at 72 hours. Patients with volume overload had increased risk of death at 90 days compared with those without volume overload (HR, 2.3; 95% CI, 1.3 to 4.2; P=0.004). Patients with AKI-D had increased risk of death at 90 days compared with those without AKI-D (HR, 2.2; 95% CI, 1.3 to 3.8; P=0.004). Volume overload remained an independent predictor of 90-day mortality when adjusting for RRT, APACHE score, weight (kg), diabetes, and heart failure (HR, 2.9; 95% CI, 1.4 to 6.0; P=0.003).

Volume overload and AKI are common and have significant prognostic value in patients treated with ECMO. Initiating RRT may help to control the deleterious effects of volume overload and improve mortality.