Prevalence, incidence and risk factors for acute renal failure in the intensive care unit

Background

Acute renal failure (ARF) is a serious complication of critical illness in the ICU. When ARF is severe enough to require renal replacement therapy, mortality approaches 50%. To evaluate interventions to prevent and treat renal failure in medical–surgical critically ill patients, a better understanding of risk factors for ARF in the ICU is needed.

Objective

To determine the independent baseline and time-dependent risk factors for ARF in a 15-bed medical–surgical closed multidisciplinary ICU in Hamilton, Canada.

Design

A prospective longitudinal cohort study.

Population

Consecutive patients admitted to the ICU during 2001 for > 72 hours. Patients were excluded if they had an admitting diagnosis of trauma, orthopedic surgery, cardiac surgery, or pregnancy, or life support withdrawal. We identified all patients requiring hemodialysis as prevalent (within 48 hours of ICU admission) or incident (after 48 hours in ICU) cases of ARF.

Methods

We recorded 49 potential risk factors for ARF on ICU admission (e.g. pre-existing comorbidities such as diabetes) and daily in the ICU (e.g. exposure to nephrotoxic antibiotics, amphotericin, contrast media, NSAIDS, diuretics and vasopressors). We also recorded strategies to prevent renal failure (e.g. N-acetyl-cysteine before contrast media exposure). We conducted Cox proportional hazard regression analysis to identify patients at risk for ARF.

Results

Among 261 admissions, 22 patients with chronic renal failure were excluded. Of 239 eligible patients, 11 had missing charts. Of 228 included patients, the mean age was 66.9 (± 15.3) and the mean APACHE II score was 25.2 (± 8.5). Dialysis was initiated within the first 48 hours of ICU admission for nine (3.9%, 95% confidence interval [CI] 1.8–7.4%) patients, and after 48 hours in the ICU for 14 (6.1%, 95% CI 3.4–10.1%) patients. The only independent risk factor for prevalent ARF was being transferred from another ICU (hazard ratio [HR] 5.6 [95% CI 1.0–30.5]). Vasopressors and/or inotropes (HR 18.2 [95% CI 1.5–220.3]) and amphotericin (HR 17.3 [95% CI 2.1–141.6]) were the independent risk factors for incident ARF.

Conclusions

In this medical–surgical critically ill population, the overall rate of ARF was 10% (prevalence 4%, incidence 6%). Patients at highest increased risk for incident ARF were those transferred from another institution; patients at highest risk for ICU-acquired ARF were those who received vasopressors and/or inotropes, or amphotericin.