Acute Kidney Injury and Risk of Death After Elective Surgery: Prospective Analysis of Data From an International Cohort Study

BACKGROUND: Postoperative acute kidney injury (AKI) is associated with a high mortality rate. However, the relationship among AKI, its associations, and mortality is not well understood. METHODS: Planned analysis of data was collected during an international 7-day cohort study of adults undergoing elective in-patient surgery. AKI was defined using Kidney Disease Improving Global Outcomes criteria. Patients missing preoperative creatinine data were excluded. We used multivariable logistic regression to examine the relationships among preoperative creatinine-based estimated glomerular filtration rate (eGFR), postoperative AKI, and hospital mortality, accounting for the effects of age, major comorbid diseases, and nature and severity of surgical intervention on outcomes. We similarly modeled preoperative associations of AKI. Data are presented as n (%) or odds ratios (ORs) with 95% confidence intervals. RESULTS: A total of 36,357 patients were included, 743 (2.0%) of whom developed AKI with 73 (9.8%) deaths in hospital. AKI affected 73 of 196 (37.2%) of all patients who died. Mortality was strongly associated with the severity of AKI (stage 1: OR, 2.57 [1.3–5.0]; stage 2: OR, 8.6 [5.0–15.1]; stage 3: OR, 30.1 [18.5–49.0]). Low preoperative eGFR was strongly associated with AKI. However, in our model, lower eGFR was not associated with increasing mortality in patients who did not develop AKI. Conversely, in older patients, high preoperative eGFR (>90 mL·minute−1·1.73 m−2) was associated with an increasing risk of death, potentially reflecting poor muscle mass. CONCLUSIONS: The occurrence and severity of AKI are strongly associated with risk of death after surgery. However, the relationship between preoperative renal function as assessed by serum creatinine-based eGFR and risk of death dependent on patient age and whether AKI develops postoperatively. Accepted for publication October 3, 2018. Funding: This was an investigator-initiated study funded by Nestle Health Sciences through an unrestricted research grant, and by a National Institute for Health Research (United Kingdom) Professorship held by R.M.P. H.C. was part-supported for this research project by the John Snow Award jointly administered by the Royal College of Anaesthetics, the British Journal of Anaesthesia, and the National Institute of Academic Anaesthesia. This study was sponsored by Queen Mary University of London. Conflicts of Interest: See Disclosures at the end of the article. Supplemental digital content is available for this article. Direct URL citations appear in the printed text and are provided in the HTML and PDF versions of this article on the journal's website (https://ift.tt/KegmMq). Members of International Surgical Outcomes Study (ISOS) group are listed in Supplemental Digital Content, https://ift.tt/2DgrGfj. International Surgical Outcomes Study investigators were entirely responsible for study design, conduct, and data analysis. The authors had full data access and were solely responsible for data interpretation, drafting, and critical revision of the manuscript, and the decision to submit for publication. Reprints will not be available from the authors. Address correspondence to John R. Prowle MD, Adult Critical Care Unit, Royal London Hospital, London, E1 1BB, United Kingdom. Address e-mail to j.prowle@qmul.ac.uk. © 2018 International Anesthesia Research Society

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