Conference Coverage

Does warfarin cause acute kidney injury?



– Patients with chronic kidney disease (CKD) and those on renin angiotensin system inhibitors and/or diuretics should have their renal function monitored during periods of overanticoagulation, results from a large retrospective study suggest.

“Unfortunately, warfarin-related nephropathy is quite hard to study,” Hugh Traquair, MD, the study’s lead author, said in an interview at the biennial summit of the Thrombosis & Hemostasis Societies of North America. “The best way to establish diagnosis is with a kidney biopsy. No one is very keen to stick a needle into a kidney when someone’s overanticoagulated. It’s been observed previously that acute kidney injury related to over-anticoagulation is more common in people with CKD, but we don’t know more about risk factors.”

Dr. Hugh Traquair of McMaster University, Hamilton, Ont Doug Brunk/MDedge News

Dr. Hugh Traquair

In an effort to better understand the association between excessive anticoagulation with warfarin and acute kidney injury (AKI) and its incidence, Dr. Traquair and his coauthors Siavash Piran, MD, Noel Chan, MD, Sam Schulman, MD, and Marlene Robinson, RN, conducted a retrospective chart review of 292 patients with an INR of 4.0 or greater who were treated at the anticoagulant clinic at McMaster University, Hamilton, Ont., between 2007 and 2017.

The primary outcome was AKI, defined as an acute increase in creatinine of greater than 26.5 micromol/L within 7-14 days of an INR 4 or greater. The secondary outcome was creatinine level within 3 months of the abnormal INR. The researchers excluded patients with AKI due to another cause, and those who lacked a creatinine level at baseline, within 7-14 days of an INR of 4 or greater, and/or at 3 months.

The median age of the 292 patients was 79 years, 55% were male, 30% were taking aspirin, and 77% were taking renin angiotensin inhibitors and/or diuretics. The control group consisted of 93 patients with a 12-month time in therapeutic range of 100%. The median age of controls was 68 years, 67% were male, and 9% had CKD. None of the controls had an AKI, said Dr. Traquair, a second-year internal medicine resident in the department of medicine at McMaster University.

Of the 292 patients with an INR of 4 or greater, 13% had an AKI, and the incidence of AKI was significantly higher in the CKD patients, compared with those who had a normal baseline creatinine level (19% vs. 10%; odds ratio, 2.1; P less than .05).

In a binomial logistic regression model, diuretic use was the only significant predictor of AKI (OR 3.4; P less than .05). The researchers also found that of the 52 patients with an INR of 4 or greater who did not use renin angiotensin system inhibitors and/or diuretics and did not have CKD, only 1 had an AKI (2%).


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