Timing of RRT based on the presence of conventional indications

No data on the development of conventional indications for RRT (refractory acidosis, hyperkalemia, uremia, oliguria/anuria, and volume overload) related to timing of RRT exist. The prevalence of conventional indications among critically ill patients on RRT for AKI was evaluated, and patients manifesting indications versus patients without indications were compared in terms of crude and adjusted 90-day mortality.

In this substudy of the Finnish Acute Kidney Injury study conducted in 2011 and 2012 in 17 intensive care units with 2901 patients, patients were classified as pre-emptive (no conventional indications) and classic (one or more indications) RRT recipients. Patients with classic RRT were divided into classic-urgent (RRT initiated ≤ 12 hours from manifesting indications) and classic-delayed (RRT >12 hours from first indication). Additionally, 2450 patients treated without RRT were matched to patients with pre-emptive RRT.

Of 239 patients treated with RRT, 134 (56.1%; 95% confidence interval [95% CI], 49.8% to 62.4%) fulfilled at least one conventional indication before commencing RRT. Crude 90-day mortality of 134 patients with classic RRT was 48.5% (95% CI, 40.0% to 57.0%), and it was 29.5% (95% CI, 20.8% to 38.2%) for the 105 patients with pre-emptive RRT. Classic RRT was associated with a higher risk for mortality (adjusted odds ratio, 2.05; 95% CI, 1.03 to 4.09). Forty-four patients with classic-delayed RRT showed higher crude mortality (68.2%; 95% CI, 54.4% to 82.0%) compared with patients with classic-urgent RRT, and this association persisted after adjustment for known confounders (odds ratio, 3.85; 95% CI, 1.48 to 10.22). Crude 90-day mortality of 67 1:1 matched patients with pre-emptive RRT was 26.9% (95% CI, 6.3% to 37.5%), and it was 49.3% (95% CI, 37.3% to 61.2%; P=0.01) for their non-RRT matches.

Patients on RRT after one or more conventional indications had both higher crude and adjusted 90-day mortality compared with patients without conventional indications. These findings require confirmation in an adequately powered, multicenter, randomized controlled trial.