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. 2016 Nov;102(5):1482-1489.
doi: 10.1016/j.athoracsur.2016.04.020. Epub 2016 Jun 17.

Acute Kidney Injury Severity and Long-Term Readmission and Mortality After Cardiac Surgery

Jeremiah R Brown  1 , William M Hisey  2 , Emily J Marshall  2 , Donald S Likosky  3 , Elizabeth L Nichols  2 , Allen D Everett  4 , Sara K Pasquali  5 , Marshall L Jacobs  6 , Jeff P Jacobs  7 , Chirag R Parikh  8
Affiliations

Acute Kidney Injury Severity and Long-Term Readmission and Mortality After Cardiac Surgery

Jeremiah R Brown et al. Ann Thorac Surg. 2016 Nov.

Abstract

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.

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Figures

Figure 1
Figure 1. 5-Year Readmission
We plot time from alive cardiac surgery discharge to the first readmission to any hospital stratified by AKIN stage: No AKI (blue line), AKIN Stage 1 (red line), and AKIN Stages 2–3 (green line). Log-rank test chi2 46.43, p-value <0.001. AKI= acute kidney injury. AKIN= Acute Kidney Injury Network.
Figure 2
Figure 2. 5-Year Mortality
We plot time from alive cardiac surgery discharge to all-cause death stratified by AKIN stage: No AKI (blue line), AKIN Stage 1 (red line), and AKIN Stages 2–3 (green line). Log-rank test chi2 56.23, p-value <0.001. AKI= acute kidney injury. AKIN= Acute Kidney Injury Network.
Figure 3
Figure 3. 5-Year Readmission or Mortality
We plot time from alive cardiac surgery discharge to readmission or all-cause death stratified by AKIN stage: No AKI (blue line), AKIN Stage 1 (red line), and AKIN Stages 2–3 (green line). Log-rank test chi2 48.49, pvalue <0.001. AKI= acute kidney injury. AKIN= Acute Kidney Injury Network.
Figure 4
Figure 4. Reasons for Hospital Readmission
This Pareto chart depicts the reasons for readmission in our cohort. The category “Other” is not included in this chart accounting for 2.5% of readmissions. Blue line shows the cumulative percentage of readmissions, and the black bars indicate the number of readmissions in this cohort.
Figure 5
Figure 5. Primary Causes of Death
Pie chart illustrates the most frequent causes of death and their percentages of occurrence in the study cohort.
See this image and copyright information in PMC

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