Severity of Chronic Kidney Disease and Outcomes After Admission to the Intensive Care Unit

Importance: Individuals with chronic kidney disease (CKD) are disproportionately admitted to the intensive care unit (ICU); however, the association between CKD severity and outcomes after ICU admission remains uncertain. Objective: To evaluate the association between CKD severity and health outcomes after ICU admission. Design, Setting, and Participants: This population-based cohort study was conducted from November 1, 2008, to February 28, 2021. Participants included 531 090 consecutive adult (≥18 years) residents of Ontario, Canada, admitted to an ICU during the study period who had a baseline outpatient serum creatinine measurement within 7 to 365 days prior to admission. Statistical analyses were conducted from July 23, 2025, to April 16, 2026. Exposure: CKD severity was classified according to the baseline outpatient estimated glomerular filtration rate (eGFR) Kidney Disease Improving Global Outcomes criteria. Main Outcomes and Measures: Mortality (ICU, hospital, and 90-day mortality) and kidney replacement therapy (KRT) requirement in the ICU and dependence at 90 days. Results: The study included 531 090 adults (mean [SD] age, 67 [15] years; 57% men) admitted to the ICU. One in 4 individuals had preexisting CKD: stage 3a CKD, eGFR 45 to 59 mL/min/1.73 m2 (12% of adults); stage 3b CKD, eGFR 30 to 44 mL/min/1.73 m2 (7% of adults); stage 4 CKD, eGFR 15 to 29 mL/min/1.73 m2 (3% of adults); non-dialysis-dependent stage 5 CKD, eGFR less than 15 mL/min/1.73 m2 (1% of adults); and undergoing maintenance dialysis (2% of adults). Compared with individuals without CKD, the severity of the disease among individuals with CKD was progressively associated with increased mortality risk up to non-dialysis-dependent stage 5 CKD. However, the risk of mortality was lower for individuals receiving maintenance dialysis (odds ratio [OR], 1.92 [95% CI, 1.82-2.04]) compared with those with non-dialysis-dependent stage 5 CKD (OR, 2.32 [95% CI, 2.14-2.52]). Risk for KRT initiation in the ICU increased with CKD severity relative to individuals without CKD: stage 3a (adjusted OR [AOR], 1.79 [95% CI, 1.68-1.90]), stage 3b (AOR, 3.02 [95% CI, 2.83-3.22]), stage 4 (AOR, 6.71 [95% CI, 6.23-7.22]), and non-dialysis-dependent stage 5 (AOR, 32.00 [95% CI, 29.07-35.22]). Among those who initiated KRT in the ICU and survived to 90 days, KRT dependence at day 90 increased progressively by CKD stage: no CKD, 7.2%; stage 3a, 14.2%; stage 3b, 22.5%; stage 4, 50.3%; and previously non-dialysis-dependent stage 5, 83.8%. Conclusions and Relevance: In this cohort study of consecutive adults admitted to the ICU, the presence and severity of CKD were associated with adverse health outcomes. These findings can inform risk prognostication, discussions about goals of care, resource allocation, and health policy initiatives for this large portion of the ICU population.