Initial continuous renal replacement therapy after stage 3 acute kidney injury without urgent dialysis indications in critically ill adults

Whether continuous renal replacement therapy (CRRT) should be routinely initiated soon after severe acute kidney injury (AKI) in critically ill adults without urgent dialysis indications remains uncertain. We emulated a target trial using MIMIC-IV among adults in their first ICU stay who newly reached KDIGO stage 3 AKI by creatinine or urine-output criteria, had no prespecified urgent dialysis indication at time zero, and remained alive and in the ICU at 24 h. We compared CRRT initiation within 24 h with initial observation during that window, allowing delayed or rescue CRRT after the landmark. Among 4,538 eligible patients, 275 (6.1%) initiated CRRT within 24 h; among the 4,263 who did not, 419 (9.8%) subsequently received delayed/rescue CRRT. After multiple imputation and overlap weighting, CRRT initiation within 24 h was associated with higher 28-day post-landmark mortality (risk difference, 0.079; 95% CI, 0.014 to 0.145) and shorter restricted mean survival time (difference, -1.666 days; 95% CI, -3.247 to -0.179). The 12-hour analysis was directionally consistent but less precise. These findings do not support a default CRRT strategy based on stage 3 AKI alone, although residual confounding remains possible.