Long-term mortality of critically ill patients with acute renal failure requiring renal replacement therapy: a 5-year population-based cohort study

Background

Despite evidence of a notoriously high short-term mortality of critically ill patients with acute renal failure (ARF), requiring renal replacement therapy (RRT), limited data exist on medium-term and long-term mortality of these patients.

Objective

To examine 90-day and 5-year mortality of critically ill patients with ARF, requiring RRT, compared with critically ill patients without ARF, requiring RRT.

Design

A population-based cohort study.

Methods

Aarhus University Intensive Care Study Cohort enabled us to identify all patients, aged 15 years or more, with first-time admission to three multidisciplinary ICUs within Aarhus University Hospital from 1999 to 2003. We obtained information on the presence of ARF requiring RRT through the study cohort. Complete follow-up on mortality was obtained from the Danish Civil Registration System. We constructed Kaplan-Meier survival curves, based on the date of ICU admission, for the main study variables (RRT: yes/no and age groups: 15–59, 60+ years) and computed contingency tables for 90-day and 5-year mortality. We computed 90-day mortality rate ratios (MRR) and 5-year MRR for patients surviving 90 days, stratified on age group.

Results

We identified 16,038 patients with a first-time ICU admission; 685 (4.3%) of those had ARF requiring RRT. The median age was 66.2 years (range 17.7–89.7) among patients with ARF requiring RRT, and 63.8 years (range 15.1–101.7) among those without ARF. Ninety-day and 5-year mortality among patients with ARF requiring RRT, aged 60+ years, was 60% and 79%, compared with 39% and 53% among those younger than 60 years (see Fig. 1). The 90-day MRR for patients with ARF requiring RRT aged 15–59 and 60+ years was 6.8 (95% CI: 5.5–8.5) and 6.2 (95% CI: 5.4–7.1) when compared with patients without ARF requiring RRT. In comparison, the corresponding 5-year MRR for patients surviving the first 90 days after ICU admission was 1.3 (95% CI: 0.8–2.0) and 1.6 (95% CI: 1.2–2.1), respectively.

Figure 1

Conclusion

ARF requiring RRT in critically ill patients is associated with a substantial increase in medium-term mortality, most markedly among elderly patients. However, among critically ill patients with ARF requiring RRT who survive the first 90 days after ICU admission, the 5-year mortality seems to be only slightly increased.