Each Added Day of Postop Antibiotics Ups Risk of Kidney Injury, C. Diff Infection

By Marilynn Larkin

NEW YORK (Reuters Health) - Each additional day of surgical antimicrobial prophylaxis increases the risks of acute kidney injury (AKI) and Clostridium difficile infection and does not lead to reductions in surgical site infections (SSIs), researchers say.

"Clinicians are often hesitant to stop antibiotics, partially because they are concerned that patients may be harmed if they are stopped too early and partially because there is limited information about the daily risk of toxicity with these medications," Dr. Westyn Branch-Elliman of the VA Boston Healthcare System in West Roxbury, Massachusetts, told Reuters Health. "Our study adds to the literature by demonstrating that every dose really does matter and provides new insight into the tangible harms of extending antibiotic courses beyond what is necessary."

"These findings add additional support to surgical guidelines that suggest that surgical antimicrobial prophylaxis should not be continued after skin closure," she said by email. "Limiting exposure to intraoperative and pre-operative doses is a rare opportunity to simultaneously improve care and reduce medical costs. In addition, these findings can be applied in other areas of clinical medicine to encourage discontinuation of medications when they are not beneficial, and potentially harmful."

Dr. Branch-Elliman and colleagues studied close to 80,000 patients (96.3% men; mean age, 65) who underwent cardiac, orthopedic total joint replacement, colorectal, and vascular procedures in the Veterans Affairs healthcare system from 2008 to 2013. All had SSI and C. difficile outcome data, and about 90% had AKI data available.

As reported online April 24 in JAMA Surgery, after stratification by surgery type and adjustment for age, sex, race, diabetes, smoking, American Society of Anesthesiologists score greater than 2, methicillin-resistant staphylococcus aureus colonization, mupirocin, type of prophylaxis, and facility factors, SSIs were not associated with the duration of prophylaxis.

By contrast, the adjusted odds of AKI increased with each additional day of prophylaxis. For a cardiac procedure, the adjusted odds ratios were 1.03 for antimicrobial treatment given for an additional 24-<48 hours; 1.22 for 48-<72 hours, and 1.82 for 72 hours or longer.

For a noncardiac procedure, the aORs were 1.31 for an additional 24-<48 hours, 1.72 for 48-<72 hours; and 1.79 for 72 hours or longer.

A similar duration-dependent association was seen for postoperative C. difficile infection: aOR, 1.08 for 24-<48 hours, 2.43 for 48-<72 hours, and 3.65 for 72 hours or longer.

The unadjusted numbers needed to harm for AKI after 24-<48 hours, 48-<72 hours, and 72 hours or more of postoperative prophylaxis were 9, 6, and 4, respectively, and 2000, 90, and 50 for C. difficile infection.

Vancomycin use was also a significant risk factor for AKI: aOR, 1.17 for a cardiac procedure and 1.21 for a noncardiac procedure.

Dr. Mary Hawn of Stanford University, coauthor of a related editorial, told Reuters Health by email, "These data are convincing and supportive of guidelines that recommend stopping antibiotics after the surgery has ended. Hospitals and surgeons should not continue prophylactic antibiotics in the post-operative period and systems should be put in place to remind surgeons to discontinue antibiotics."

SOURCE: https://bit.ly/2vxJvSc and https://bit.ly/2vyjO3G

JAMA Surg 2019.

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