Patients with serum creatinine levels that return to less than 1.5 x baseline within 30 days of experiencing postsurgical acute kidney injury (AKI) appear to have the best 1-year survival rates, a new study suggests. And because a universally accepted definition of AKI recovery does not exist, this finding may serve as a useful standard.

Study results were presented by Thorir E. Long, MD, PhD, of the University of Iceland, at the American Society of Nephrology's annual meeting held October 31 to November 5, 2017, in New Orleans, LA. Other investigators involved in the study included Sòlveig Helgadòtrttir, MD, of Akademiska Hospital Uppsala University, and Martin I. Sigurdsson, MD, of Duke.

The goal of this retrospective study was to examine different definitions of renal recovery with survival rates of individuals who experienced postsurgical AKI. Data on serum creatinine (SCr) levels were extracted from electronic medical records for adult patients who underwent orthopaedic, abdominal, vascular, or cardiothoracic surgery at the University Hospital in Reykjavik, Iceland, between 1998 and 2015. Patients with a baseline estimated glomerular filtration rate less than 15 mL/min/1.73 m² were excluded, as were those who died during the index admission or had recurrent AKI episodes.

A total of 2,410 patients experienced postsurgical AKI, and logistic regression was used to examine associations between 1-year survival and various degrees of renal recovery (SCr reduction to less than 1.5, 1.25, and 1.1 x baseline) and time points (10, 20, and 30 days post-AKI) in these patients.

The analyses revealed that all recovery definitions (ie, SCr < 1.5, 1.25, or 1.1 x baseline at 10, 20, or 30 days post-surgery) were significantly associated with 1-year survival. Reaching an SCr less than 1.5 x baseline within 30 days, however, had the strongest relationship with 1-year survival in a multivariable logistic model that adjusted for a host of factors including age, year of the AKI episode, stage of AKI, comorbid conditions, and others (OR, 0.37; 95% CI, 0.29-0.48; P < .001). The risk of 1-year mortality was higher in those who had persistent SCr levels of 1.5 x baseline following AKI than it was in those whose SCr returned to less than 1.1 x baseline (Table 1).

TABLE 1. Adjusted Odds Ratio for 1-Year Mortality

In patients with postoperative AKI who survived to hospital discharge, achieving SCr less than 1.5 x baseline within 30 days had the strongest association with 1-year survival, the study found. "This might, therefore, be a useful definition of renal recovery after AKI," concluded Long.

Source: Long TE, Helgadòttir S, Helgason D, et al. Defining renal recovery following postoperative AKI. Presented at: American Society of Nephrology annual meeting, Kidney Week 2017; October 31-November 5, 2017; New Orleans, LA. Oral Presentation 105.