RS22 - Prediction Model for Safe Contrast Volume Thresholds – Preventing Postcontrast Acute Kidney Injury to Decrease Mortality after Endovascular Abdominal Aortic Aneurysm Repair

Objectives: Post-contrast acute kidney injury (PC-AKI) is a dreadful complication of Endovascular Abdominal Aortic Aneurysm Repair (EVAR) and is associated with development of CKD, prolonged hospital stay, and perioperative mortality. Iodinated contrast is a known risk factor for PC-AKI but a technical necessity for EVAR. The optimal volumes of contrast necessary to minimize risk of PC-AKI in patients undergoing elective EVAR are unknown. This study examines the incidence and significance of PC-AKI after EVAR and derives a patient-specific model to determine optimal volume of contrast the surgeon should administer to mitigate risk of PC-AKI.

Methods: The VQI database was queried for patients who underwent elective EVAR. Patients with history of dialysis, kidney transplant, intraoperative coverage of a renal artery, or open conversion were excluded. Patients were stratified by development of PC-AKI. Patient characteristics were compared using bivariate and then regression analysis to select significant variables. A prediction model was developed for PC-AKI using a split-sample approach with a model training dataset and validation dataset. Analysis was repeated for perioperative mortality, and Kaplan-Meier (KM) analysis compared survival between groups.

Results: Among 49,417 patients undergoing elective EVAR, 2.6% (n=1,300) developed PC-AKI. Patients with PC-AKI were older with higher incidence of preoperative comorbidities and developed significantly more postoperative complications including 30-day mortality (12% vs 0.5%, P< 0.001) compared to patients without PC-AKI (Table I). Patients who developed PC-AKI also had lower survival on KM analysis (2-year survival: 74.5% vs 82.8%, P< 0.001). Regression analysis accounted for all other factors and showed that PC-AKI was significantly associated with perioperative mortality (OR: 8.79).

On multivariate analysis (Table II), PC-AKI was independently associated with volume of contrast (OR per mL: 1.005) translating to a 5% increased PC-AKI risk for every 10mL of contrast administered. The prediction model (AUC: 0.732; 95%CI=0.706-0.759) allows physicians to preoperatively input values for 13 patient-specific factors to determine the safe volume of contrast to keep the risk of PC-AKI < 3%. Table II demonstrates theoretical patient examples and shows how increasing severity of risk factors corresponds to lower recommended contrast volumes.

Conclusions: PC-AKI has significant impact on patient morbidity and mortality after elective EVAR. The model provided allows physicians to input 13 simple, patient-specific variables to immediately generate a recommended contrast volume to minimize PC-AKI risk. In the absence of established guidelines for optimal volume of contrast to administer during elective EVAR, this model can serve as an important guide for surgeons prior to performing EVAR.