Frailty and Outcomes in Critically Ill Patients Receiving Continuous Renal Replacement Therapy: A Nationwide Swedish Cohort Study

This is a nationwide, registry-based observational cohort study of critically ill patients treated in intensive care units in Sweden. The study will use data from the Swedish Intensive Care Registry (SIR), which collects information from intensive care units across Sweden.

The primary focus is on critically ill patients receiving continuous renal replacement therapy (CRRT), with particular emphasis on older patients and the prognostic role of frailty. The study will investigate whether the Clinical Frailty Scale (CFS) and measures of comorbidity and illness severity provide prognostic information beyond chronological age.

The cohort will include eligible adult ICU patients receiving CRRT during their ICU stay. Baseline characteristics, including age and sex, will be assessed at ICU admission. Illness severity will be described using the Simplified Acute Physiology Score 3 (SAPS3), including estimated mortality risk. Additional variables will include comorbidities, ICU admission characteristics, discharge diagnosis, and CRRT-related treatment information available in the registry.

Mortality follow-up will be conducted through available registry data and linkage to the Swedish Cause of Death Register. Outcomes will be assessed at predefined time points, including 30, 60, 90, and 365 days following ICU admission.

The study is observational and registry-based. Investigators will not assign CRRT treatment or perform research procedures on patients. Statistical analyses will include descriptive methods, survival analyses, and multivariable regression to evaluate associations between frailty, age, illness severity, and clinical outcomes.

Inclusion criteria

Patients aged 18 years or older. Patients treated in an intensive care unit in Sweden. Patients receiving continuous renal replacement therapy (CRRT) during the ICU stay.

ICU admissions occurring between January 1, 2012, and August 15, 2024, subject to confirmation of the final study period.

Exclusion criteria

Age below 18 years. No treatment with CRRT during the ICU stay. Concealed or temporary personal identity number. Invalid registration date of death. Emigration within 30 days after ICU admission. Missing SAPS3 score.