Determinants of acute kidney injury duration after cardiac surgery: an externally validated tool.
BACKGROUND
Acute kidney injury (AKI) duration after cardiac surgery is associated with poor survival in a dose-dependent manner. However, it is not known what perioperative risk factors contribute to prolonged AKI and delayed recovery. We sought to identify perioperative risk factors that predict duration of AKI, a complication that effects short and long-term survival.


METHODS
We studied 4,987 consecutive cardiac surgery patients from 2002 through 2007. Acute kidney injury was defined as a 0.3 or greater (mg/dL) or 50% or greater increase in serum creatinine from baseline. Duration of AKI was defined by the number of days AKI was present. Stepwise multivariable negative binomial regression analysis was conducted using perioperative risk factors for AKI duration. The c-index was estimated by Kendall's tau.


RESULTS
Acute kidney injury developed in 39% of patients with a median duration of AKI at 3 days and ranged from 1 to 108 days. Patients without AKI had a duration of 0 days. Independent predictors of AKI duration included baseline patient and disease characteristics, and operative and postoperative factors. Prediction for mean duration of AKI was developed using coefficients from the regression model and externally validated the model on 1,219 cardiac surgery patients in a separate cardiac surgery cohort (Translational Research Investigating Biomarker Endpoints-AKI). The c-index was 0.65 (p<0.001) for the derivation cohort and 0.62 (p<0.001) for the validation cohort.


CONCLUSIONS
We identified and externally validated perioperative predictors of AKI duration. These risk factors will be useful to evaluate a patient's risk for the tempo of recovery from AKI after cardiac surgery and subsequent short and long-term survival. The levels of awareness created by working with these risk factors have implications regarding positive changes in processes of care that have the potential to decrease the incidence and mitigate AKI.
The Dartmouth Institute for Health Policy and Clinical Practice, Section of Cardiology Dartmouth-Hitchcock Medical Center, and Dartmouth Medical School, Lebanon, New Hampshire 03756, USA. jbrown@dartmouth.edu
Jeremiah R
JR
Brown
Robert S
RS
Kramer
Todd A
TA
MacKenzie
Steven G
SG
Coca
Kyaw
K
Sint
Chirag R
CR
Parikh
D058186:Acute Kidney Injury / Q000097:blood / Q000453:epidemiology* / Q000209:etiology; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D015415:Biomarkers; D006348:Cardiac Surgical Procedures; D002316:Cardiotonic Agents / Q000627:therapeutic use; D015897:Comorbidity; D001026:Coronary Artery Bypass / Q000379:methods / Q000706:statistics & numerical data; D003404:Creatinine / Q000097:blood; D004906:Erythrocyte Count; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011183:Postoperative Complications / Q000453:epidemiology* / Q000209:etiology; D012189:Retrospective Studies; D012307:Risk Factors; D013318:Stroke Volume; D013997:Time Factors
D015415:Biomarkers; D002316:Cardiotonic Agents; D003404:Creatinine