The following is a summary of “Proenkephalin A 119–159 predicts early and successful liberation from renal replacement therapy in critically ill patients with acute kidney injury: a post hoc analysis of the ELAIN trial” published in the October 2022 issue of Critical Care by Groote et al.

For patients in critical care who have suffered severe acute kidney injury (AKI), renal replacement therapy (RRT) is still the primary form of rescue treatment. However, no methods exist at this time to accurately foretell whether or not RRT will be successfully evaded. The use of biomarkers can potentially facilitate risk classification and the customization of therapeutic approaches. RRT liberation in critically ill patients with AKI has not yet been tested, although proenkephalin A 119-159 (penKid) has been proposed as a prospective marker of kidney function in the setting of AKI. The blood levels of penKid were analyzed in this post hoc study, which comprised 210 participants from the randomized clinical ELAIN trial. Both a landmark analysis on day 3 post-RRT initiation and a time-to-event risk analysis performed on pre-RRT penKid revealed conflicting results. Success in overcoming RRT and mortality without RRT victory were competing for risk endpoints.

Patients with low pre-RRT penKid levels (penKid 89 pmol/l) at RRT initiation were more likely to be successfully liberated from RRT than those with high pre-RRT penKid levels (subdistribution hazard ratio (sHR) 1.83, 95% CI 1.26–2.67, P=0.002, estimated 28d-cumulative incidence function (28d-CIF) of successful liberation from RRT 61% vs. 45%, P=0.022).  The landmark analysis performed on day 3 of RRT confirmed this connection (sHR 1.78, 95% CI 1.17-2.71, P=0.007; 28-day CIF of effective escape from RRT, 67% vs. 47%, P=0.018). There was no discernible change in the mortality rate between the 2 periods.

Plasma penKid seems to be a valuable biomarker for the prediction of shorter duration and successful liberation from RRT in critically ill patients with RRT-dependent AKI, and it may allow for a customized strategy to guide strategies of RRT liberation.