Acute Kidney Injury Severity and Long-Term Readmission and Mortality After Cardiac Surgery.
BACKGROUND
Acute kidney injury (AKI) is a common complication after cardiac surgery. While AKI severity is known to be associated with increased risk of short-term outcomes, its long-term impact is less well understood.


METHODS
Adult patients undergoing isolated coronary artery bypass graft surgery at eight centers were enrolled into the Northern New England biomarker registry (n = 1,610). Patients were excluded if they had renal failure (n = 15) or died during index admission (n = 38). Severity of AKI was defined using the Acute Kidney Injury Network (AKIN). We linked our cohort to national Medicare and state all-payer claims to ascertain readmissions and to the National Death Index to ascertain survival. Kaplan-Meier and multivariate Cox proportional hazards modeling was conducted for time to readmission and death over 5 years.


RESULTS
Within 5 years, 513 patients (33.8%) had AKI with AKIN stage 1 (29.9%) and stage 2 to 3 (3.9%). There were 620 readmissions (39.9%) and 370 deaths (23.8%). After adjustment, stage 1 AKI patients had a 31% increased risk of readmission (95% confidence interval [CI]: 1.10 to 1.57), whereas stage 2 or 3 patients had a 98% increased risk (95% CI: 1.41 to 2.78) compared with patients having no AKI. Relative to patients without AKI, stage 1 patients had a 56% increased risk of mortality (95% CI: 1.14 to 2.13), whereas stage 2 or 3 patients had a 3.5 times higher risk (95% CI: 2.16 to 5.60).


CONCLUSIONS
Severity of AKI using the AKIN stage criteria is associated with a significantly increased risk of 5-year readmission and mortality. Our findings suggest that efforts to reduce AKI in the perioperative period may have a significant long-term impact on patients and payers in reducing mortality and health care utilization.
Dartmouth Institute for Health Policy and Clinical Practice, Geisel School of Medicine, Lebanon, New Hampshire; Department of Medicine, Geisel School of Medicine, Lebanon, New Hampshire. Electronic address: jbrown@dartmouth.edu.
Jeremiah R
JR
Brown
Dartmouth Institute for Health Policy and Clinical Practice, Geisel School of Medicine, Lebanon, New Hampshire.
William M
WM
Hisey
Dartmouth Institute for Health Policy and Clinical Practice, Geisel School of Medicine, Lebanon, New Hampshire.
Emily J
EJ
Marshall
Department of Cardiac Surgery, University of Michigan, Ann Arbor, Michigan.
Donald S
DS
Likosky
Dartmouth Institute for Health Policy and Clinical Practice, Geisel School of Medicine, Lebanon, New Hampshire.
Elizabeth L
EL
Nichols
Department of Pediatrics, Johns Hopkins School of Medicine, Baltimore, Maryland.
Allen D
AD
Everett
Department of Pediatrics and Communicable Diseases, University of Michigan C. S. Mott Children's Hospital, Ann Arbor, Michigan.
Sara K
SK
Pasquali
Division of Cardiac Surgery, Department of Surgery, Johns Hopkins University, Baltimore, Maryland.
Marshall L
ML
Jacobs
Johns Hopkins All Children's Heart Institute, All Children's Hospital and Florida Hospital for Children, Saint Petersburg, Florida.
Jeff P
JP
Jacobs
Department of Internal Medicine and Program of Applied Translational Research, Yale University School of Medicine, Temple Medical Center, New Haven, Connecticut.
Chirag R
CR
Parikh
D058186:Acute Kidney Injury / Q000097:blood / Q000453:epidemiology* / Q000209:etiology / Q000401:mortality; D000368:Aged; D002423:Cause of Death; D001026:Coronary Artery Bypass; D003404:Creatinine / Q000097:blood; D016208:Databases, Factual; D005260:Female; D006801:Humans; D053208:Kaplan-Meier Estimate; D008297:Male; D008875:Middle Aged; D009511:New England / Q000453:epidemiology; D010359:Patient Readmission / Q000706:statistics & numerical data*; D011183:Postoperative Complications / Q000453:epidemiology* / Q000209:etiology / Q000401:mortality; D016016:Proportional Hazards Models; D012189:Retrospective Studies; D012306:Risk; D012307:Risk Factors; D012720:Severity of Illness Index
D003404:Creatinine