Mortality and Rate of Net Ultrafiltration in Critically Ill Patients

More than two-thirds of critically ill patients with acute kidney injury (AKI) experience fluid overload, a complication that is independently associated with mortality. International practice guidelines recommend net ultrafiltration (NUF) in patients with fluid overload that is resistant to treatment with diuretics. Results from previous studies have suggested that NUF could reduce the number of deaths in that patient population. However, according to Raghavan Murugan, MD, MD, FRCP, and colleagues, there are few data available regarding the optimal rate of NUF in critically ill patients.

The Randomized Evaluation of Normal vs Augmented Level (RENAL) of Renal Replacement Therapy trial included 1434 patients with AKI being treated with continuous venovenous hemodiafiltration. Patients were stratified into three groups based on net ultrafiltration rate: high (NUF rate >1.75 mL/kg/h); middle (NUF rate from 1.01 to 1.75 mL/kg/h); and low (NUF rate <1.01 mL/kg/h).

There was no association with death from day 0 to day 6 in the high-tertile group compared with the low-tertile group. However, from day 7 to day 12, death occurred in 51 patients in the high-tertile group versus 30 patients in the low-tertile group. From day 13 to day 26, there were 45 deaths in the high-tertile group versus 25 in the low-tertile group; from day 27 to 90, there were 48 deaths in the high-tertile group versus 29 in the low-tertile group.

“Among critically ill patients, NUF rates >1.75 mL/kg/h compared with NUF rates <1.01 mL/kg/h were associated with lower survival. Residual confounding may be present from unmeasured risk factors, and randomized clinical trials are required to confirm these findings,” the researchers said.