Intensive Care Unit Renal Replacement Therapy: Less Is More (or Better)

CONTINUOUS KIDNEY REPLACEMENT THERAPY DOSAGE AND MORTALITY IN CRITICALLY ILL PATIENTS: A RETROSPECTIVE COHORT STUDY USING MARGINAL STRUCTURAL MODEL

ABSTRACT

Background : Continuous kidney replacement therapy (CKRT) is a crucial intervention for hemodynamically unstable patients with acute kidney injury (AKI). Despite the recommendations to offer a CKRT dose of 20 to 25 mL/kg/h, the optimal CKRT dose remains uncertain, especially whether low-dose CKRT is associated with poor outcomes. This study investigated the association between low CKRT dosage and 90-day mortality using a marginal structural model (MSM). Methods : Using the MIMIC-IV database, adult patients who received CKRT for more than 24 h were included. Data on time-fixed and time-dependent variables were collected. Patients were categorized based on CKRT dose thresholds of 13 and 20 mL/kg/h. Results : Among the 1,329 patients, the 90-day mortality rate was 49.6%. The median age of the patients was 62 years (IQR: 52-72). Changes in CKRT dosing during treatment were frequent. Patients with a reduced delivered CKRT dose (<20 and <13 mL/kg/h) generally exhibited low values during the initial days of CKRT, with an increase in the delivered CKRT dose. After adjusting only for baseline variables (traditional Cox regression model), patients receiving CKRT doses <13 mL/kg/h had significantly greater 90-day mortality (HR: 1.70, 95% CI 1.16-2.49) than those receiving CKRT doses ≥13 mL/kg/h. However, after adjusting for time-dependent variables, the CKRT dose was not significantly associated with mortality at either the 13 or 20 mL/kg/h threshold. Additionally, there were no significant associations between the delivered CKRT dose and 90-day mortality within the range of 5 to 40 mL/kg/h. Conclusion : This study highlights the impact of methodological approaches on the association between CKRT dose and mortality and that with personalized adjustments, there may not be a lower limit of the unsafe CKRT dose. However, lower CKRT doses were initially associated with higher mortality, and adjusting for time-dependent variables nullified this association.

Low-Dose Continuous Kidney Replacement Therapy and Mortality in Critically Ill Patients With Acute Kidney Injury: A Retrospective Cohort Study

RATIONALE & OBJECTIVE

Continuous kidney replacement therapy (CKRT) is preferred when available for hemodynamically unstable acute kidney injury (AKI) patients in the intensive care unit (ICU). The Kidney Disease: Improving Global Outcomes (KDIGO) guidelines recommend a delivered CKRT dose of 20-25mL/kg/h; however, in Japan the doses are typically below this recommendation due to government health insurance system restrictions. This study investigated the association between mortality and dose of CKRT.

STUDY DESIGN

Single-center retrospective cohort study.

SETTING & PARTICIPANTS

Critically ill patients with AKI treated with CKRT at a tertiary Japanese university hospital between January 1, 2012, and December 31, 2021.

EXPOSURE

Delivered CKRT doses below or above the median.

OUTCOME

90-day mortality after CKRT initiation.

ANALYTICAL APPROACH

Multivariable Cox regression analysis and Kaplan-Meier analysis.

RESULTS

The study population consisted of 494 patients. The median age was 72 years, and 309 patients (62.6%) were men. Acute tubular injury was the leading cause of AKI, accounting for 81.8%. The median delivered CKRT dose was 13.2mL/kg/h. Among the study participants, 456 (92.3%) received delivered CKRT doses below 20mL/kg/h, and 204 (41.3%) died within 90 days after CKRT initiation. Multivariable Cox regression analysis revealed increased mortality in the below-median group (HR, 1.73 [95% CI, 1.19-2.51], P=0.004). Additionally, a significant, inverse, nonlinear association between 90-day mortality and delivered CKRT dose was observed using delivered CKRT dose as a continuous variable.

LIMITATIONS

Single-center, retrospective, observational study.

CONCLUSIONS

A lower delivered CKRT dose was independently associated with higher 90-day mortality among critically ill patients who mostly received dosing below the current KDIGO recommendations.

PLAIN-LANGUAGE SUMMARY

The Kidney Disease: Improving Global Outcomes (KDIGO) guidelines recommend delivering a continuous kidney replacement therapy (CKRT) dose of 20-25mL/kg/h. However, it is not clear if it is safe to use delivered CKRT doses below this recommendation. In this study, over 90% of the patients received CKRT with a delivered dose below the KDIGO recommendation. We divided these patients into 2 groups based on the median delivered CKRT dose. Our findings show that a delivered CKRT dose below the median was associated with increased risk of death within 90 days. These findings show that a lower delivered CKRT dose was independently associated with higher 90-day mortality among critically ill patients who mostly received dosing below current KDIGO recommendations.