Original Investigation
Pathogenesis and Treatment of Kidney Disease
Acute Kidney Injury After Major Surgery: A Retrospective Analysis of Veterans Health Administration Data

https://doi.org/10.1053/j.ajkd.2015.07.022Get rights and content

Background

Few trials of acute kidney injury (AKI) prevention after surgery have been conducted, and most observational studies focus on AKI following cardiac surgery. The frequency of, risk factors for, and outcomes after AKI following other types of major surgery have not been well characterized and may present additional opportunities for trials in AKI.

Study Design

Observational cohort study.

Setting & Participants

3.6 million US veterans followed up from 2004 to 2011 for the receipt of major surgery (cardiac; general; ear, nose, and throat; thoracic; vascular; urologic; and orthopedic) and postoperative outcomes.

Factors

Demographics, health characteristics, and type of surgery.

Outcomes

Postoperative AKI defined by the KDIGO creatinine criteria, postoperative length of stay, end-stage renal disease, and mortality.

Results

Postoperative AKI occurred in 11.8% of the 161,185 major surgery hospitalizations (stage 1, 76%; stage 2, 15%, stage 3 [without dialysis], 7%; and AKI requiring dialysis, 2%). Cardiac surgery had the highest postoperative AKI risk (relative risk [RR], 1.22; 95% CI, 1.17-1.27), followed by general (reference), thoracic (RR, 0.92; 95% CI, 0.87-0.98), orthopedic (RR, 0.70; 95% CI, 0.67-0.73), vascular (RR, 0.68; 95% CI, 0.64-0.71), urologic (RR, 0.65; 95% CI, 0.61-0.69), and ear, nose, and throat (RR, 0.32; 95% CI, 0.28-0.37) surgery. Risk factors for postoperative AKI included older age, African American race, hypertension, diabetes mellitus, and, for estimated glomerular filtration rate < 90 mL/min/1.73 m2, lower estimated glomerular filtration rate. Participants with postoperative AKI had longer lengths of stay (15.8 vs 8.6 days) and higher rates of 30-day hospital readmission (21% vs 13%), 1-year end-stage renal disease (0.94% vs 0.05%), and mortality (19% vs 8%), with similar associations by type of surgery and more severe stage of AKI relating to poorer outcomes.

Limitations

Urine output was not available to classify AKI; cohort included mostly men.

Conclusions

AKI was common after major surgery, with similar risk factor and outcome associations across surgery type. These results can inform the design of clinical trials in postoperative AKI to the noncardiac surgery setting.

Section snippets

Study Population

The study population was derived from a large cohort consisting of all patients with estimated glomerular filtration rates (eGFRs) ≥ 60 mL/min/1.73 m2 (calculated by the CKD-EPI [CKD Epidemiology Collaboration] creatinine equation23) measured between October 1, 2004, and September 30, 2006, in the national Veterans Affairs (VA) Corporate Data Warehouse LabChem data files, with follow-up until September 15, 2011 (N = 3,582,478).24 For the present study, patients were included at the first instance

Baseline Characteristics

Among the 161,185 participants who underwent an eligible major surgery during the study period, mean age was 64 years, 96.3% were men, and 16.9% were African American (Table 1). Average blood pressure in the year prior to surgery was 133/76 mm Hg, and average BMI was 29 kg/m2. Mean eGFR was 80 mL/min/1.73 m2, and 12.0% of the population had eGFRs < 60 mL/min/1.73 m2. The most common type of surgery was general (27.7%), followed by orthopedic (20.8%), vascular (16.5%), and cardiac (13.8%). Persons

Discussion

In this national study of US veterans undergoing major surgery, the overall rate of postoperative AKI was 11.8%, ranging from 4.1% after ENT surgery to 13.2% after general surgery to 18.7% after cardiac surgery. Risk factors for postoperative AKI were fairly uniform by type of surgery and consistently included African American race, higher BMI, liver disease, and lower eGFR if eGFR was <90 mL/min/1.73 m2. Higher AKI stage was associated with worse outcomes. Results were robust to different

Acknowledgements

Some aspects of this study were presented as a poster at the American Society of Nephrology Annual Kidney Week on November 13, 2014, in Philadelphia, PA.

Some of the data reported here have been supplied by the US Renal Data System. The interpretation and reporting of these data are the responsibility of the authors and in no way should be seen as an official policy or interpretation of the US government.

Support: Dr Grams receives support from the National Institute of Diabetes and Digestive and

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