Incidence and risk factors for acute kidney injury in patients with excessive anticoagulation on warfarin: a retrospective study

Anticoagulant-related nephropathy is an acute kidney injury (AKI) associated with excessive anticoagulation. The nature of the association between excessive anticoagulation with warfarin and AKI and its incidence remain unclear. To evaluate the incidence of AKI in excessively anticoagulated patients taking warfarin and examine potential risk factors. A retrospective chart review was performed in patients on chronic warfarin. The primary outcome was AKI, defined as an acute increase in creatinine of > 26.5 µmol/L within 7–14 days of an international normalized ratio (INR) ≥ 4.0. 292 patients with an INR ≥ 4.0 were included. 101 patients had CKD and 191 did not have CKD. Of the 292 patients with an INR ≥ 4.0, 38 (13%) had an AKI. In univariable analyses, CKD [odds ratio (OR) 2.1, 95% confidence interval (CI) 0.99–4.43] and use of renin–angiotensin system (RAS) blockers and/or diuretics (OR 3.85; 95% CI 1.15–20.15) were significantly associated with the risk of AKI. In a binomial logistic regression model, use of RAS blockers and/or diuretics was the only significant predictor of AKI (OR 3.4; 95% CI 1.02–11.76). Use of RAS blockers and/or diuretics significantly increased the risk of AKI in patients with warfarin-related excessive anticoagulation. Further prospective studies examining the association of high INRs and AKI are needed.