The Society for Vascular Surgery Vascular Quality Initiative Underestimates the Risk Associated with Mild Postoperative Acute Kidney Injury.

Objective: Recently the American College of Surgeons National Surgical Quality Improvement Program (ACS NSQIP) lowered the thresholds for acute kidney injury (AKI) to align with the Kidney Disease: Improving Global Outcomes (KDIGO) definition (>0.3 mg/dL change from the reference serum creatinine (sCr) within 48 hours of surgery or initiation of dialysis). The Vascular Quality Initiative (VQI) defines postoperative renal dysfunction as a rise in serum creatinine >0.5mg/dL from baseline or new postoperative temporary or permanent dialysis throughout the postoperative course. This definition does not align with guidelines outside of VQI and may not capture subtle changes in perioperative renal function that can impact patient outcomes.

Methods: Single institution retrospective review of adult patients with no previous history of preoperative hemodialysis undergoing elective or nonelective major vascular surgery that were registered with the VQI. Patients undergoing endovascular abdominal or thoracic aortic repair, open abdominal aortic aneurysm repair, and suprainguinal or infrainguinal bypasses were included.

Results: A total of 932 patients were included. AKI occurred in 6% of patients using the VQI definition (VQI-AKI), as compared to 18% of patients using a modified KDIGO definition (>0.3 mg/dL change from the reference serum creatinine (sCr) within 48 hours of surgery or initiation of dialysis (mKDIGO-AKI). Regardless of the definition used, patients with AKI had longer postoperative length of stay and higher morbidity and mortality. One-year survival was lower for VQI-AKI patients versus mKDIGO-AKI patients, 57% vs. 77%, respectively (log-rank p<.001). In a multivariable cox regression model adjusting for age, nonelective admission status, and history of congestive heart failure, patients with mKDIGO-AKI had 2.5x higher odds of postoperative mortality compared to patients without AKI.

Conclusions: The current VQI definition underestimates the rate of clinically significant AKI when compared to mKDIGO, as patients with newly identified AKI using the mKDIGO definition are associated with increased postoperative complications and decreased survival as compared to those without AKI. Given the importance of AKI on short and long-term outcomes, the inclusion of preoperative and highest postoperative creatinine within 7 days of surgery among patients at high risk for postoperative AKI (open AAA, supra/infrainguinal bypass, TEVAR, and EVAR) may be warranted to facilitate appropriate benchmarking and quality improvement efforts.