Background The risk of developing a persistent reduction in renal function after postoperative acute kidney injury (pAKI) is not well-established.

Objective Perform a multi-center retrospective propensity matched study evaluating whether patients that develop pAKI have a greater decline in long-term renal function than patients that did not develop postoperative AKI.

Design Multi-center retrospective propensity matched study.

Setting Anesthesia data warehouses at three tertiary care hospitals were queried.

Patients Adult patients undergoing surgery with available preoperative and postoperative creatinine results and without baseline hemodialysis requirements.

Measurements The primary outcome was a decline in follow-up glomerular filtration rate (GFR) of 40% relative to baseline, based on follow-up outpatient visits from 0-36 months after hospital discharge. A propensity score matched sample was used in Kaplan-Meier analysis and in a piecewise Cox model to compare time to first 40% decline in GFR for patients with and without pAKI.

Results A total of 95,208 patients were included. The rate of pAKI ranged from 9.9% to 13.7%. In the piecewise Cox model, pAKI significantly increased the hazard of a 40% decline in GFR. The common effect hazard ratio was 13.35 (95% CI: 10.79 to 16.51, p<0.001) for 0-6 months, 7.07 (5.52 to 9.05, p<0.001) for 6-12 months, 6.02 (4.69 to 7.74, p<0.001) for 12-24 months, and 4.32 (2.65 to 7.05, p<0.001) for 24-36 months.

Limitations Retrospective; Patients undergoing ambulatory surgery without postoperative lab tests drawn before discharge were not captured; certain variables like postoperative urine output were not reliably available.

Conclusion Postoperative AKI significantly increases the risk of a 40% decline in GFR up to 36 months after the index surgery across three institutions.

Dr. Hofer is the founder and President of Extrico health a company that helps hospitals leverage data from their electronic health record for decision making purposes. The Extrico platform was used to obtain data for this study from all sites. Dr. Hofer receives research support and serves as a consultant for Merck. This work was funded by NIH grant 1K01HL150318. Dr. Gabel has equity in Extrico Health. The Extrico platform was used to obtain data for this study from all sites.

This work was funded by NIH grant 1K01HL150318.

I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained.

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The details of the IRB/oversight body that provided approval or exemption for the research described are given below:

Data were collected from departmental anesthesia data warehouses at Mount Sinai Hospital (MSH), the University of Miami (UM), and the University of California Los Angeles (UCLA). Institutional Review Board approval was obtained at each respective institution with waiver of informed consent (MSH: 19-01166-CR003; UM: 15-000518).

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All data produced in the present study are available upon reasonable request to the authors