Who is at increased risk for acute kidney injury following noncardiac surgery?

Abelha and colleagues evaluated the incidence and determinants of postoperative acute kidney injury (AKI) after major noncardiac surgery in patients with previously normal renal function. In this retrospective study of 1,166 patients with no previous renal insufficiency, who were admitted to a postsurgical intensive care unit (ICU) over a 2-year period, the incidence of AKI was 7.5%. Multivariate analysis identified American Society of Anesthesiologists physical status, Revised Cardiac Risk Index, high-risk surgery and congestive heart disease as preoperative AKI risk factors. AKI was an independent risk factor for hospital mortality (odds ratio = 3.12, 95% confidence interval = 1.41 to 6.93; P = 0.005), and was associated with higher severity of illness scores (Simplified Acute Physiology Score II and Acute Physiology and Chronic Health Evaluation II), longer ICU length of stay, higher ICU mortality, increased hospital mortality and higher mortality at 6-month follow up. Although the study design excluded 121 patients with significant preoperative renal insufficiency by design, the relatively crude serum creatinine cut-offs used certainly permitted inclusion of numerous patients with preoperative renal impairment. Accordingly, the study design failed to quantify the impact of preoperative renal impairment on risk and outcomes of perioperative AKI in noncardiac surgery, and this should be a goal of such studies in the future. Nonetheless, the study is an important addition to the literature in an under-studied population of patients at high risk for AKI.