Mild AKI is associated with mortality of patients who underwent cardiopulmonary bypass surgery

Acute kidney injury (AKI) stage I is the most common stage of AKI observed among patients who underwent cardiac surgery with cardiopulmonary bypass (CPB). The relationship between AKI stage I and mortality requires further investigation. Patients aged 18 years or older who underwent cardiac surgery with CPB between July 1, 2013 and May 31, 2014, were reviewed in the present study. Patients were dichotomized into: i) The AKI stage I group, and ii) the non-AKI group. The primary measured characteristic in the present study was the relationship between AKI and mortality. Kaplan-Meier survival analyses were taken to obtain survival curves. A total of 1,846 patients were included in this present study. The mean age was 51.76±13.56 years. A total of 1,508 patients did not develop AKI and 338 developed AKI stage I. The mean follow-up period among survivors was 9.95±3.45 months. Kaplan-Meier survival analyses showed that patients with AKI stage I were at an increased mortality risk (P<0.0001). In multivariate Cox regression analysis, AKI stage I remained independently associated with a reduced survival. Using a subgroup analysis, patients with non-recovery AKI (defined as non-recovery AKI if the serum level does not return before surgery) had a higher mortality rate than patients with recovery AKI (P<0.0001). AKI stage I is the most common form of AKI and it is independently related to all-cause mortality in patients who underwent cardiovascular surgery with cardiopulmonary bypass.