What’s New in the Patient Safety World

May 2019

Focus on Prophylactic Antibiotic Duration



Prophylactic antibiotics are important for reducing the risk of surgical site infections (SSI’s) for many surgical procedures. We know from previous studies that benefits of antimicrobial prophylaxis are limited to the first 24 hours postoperatively. Hence, guidelines and patient safety initiatives have been focused not only on the timing of administration of prophylactic antibiotics, but also on ensuring that such are promptly discontinued following surgical procedures.


Most national guidelines and quality measures state that surgical antimicrobial prophylaxis be initiated <1 hour prior to surgery and discontinued <24 hours post-operatively, and <48 hours for cardiac surgery. Notably, several surgical societies have noted lack of evidence that continuing prophylactic antibiotics after wound closure reduces SSI’s and thus recommend cessation of prophylactic antibiotics at the time the wound has been closed, with certain exceptions (Ban 2017).


A new study focused on the harms of longer duration of exposure to such prophylactic antibiotics (Branch-Elliman 2019). The study looked at patients who underwent cardiac, orthopedic total joint replacement, colorectal, and vascular procedures within the national Veterans Affairs health care system. The researchers separated duration of postoperative antimicrobial prophylaxis into the following categories: <24 hours, 24-<48 hours, 48-<72 hours, and ≥72 hours. They found that increasing duration of antimicrobial prophylaxis was associated with higher odds of acute kidney injury (AKI) and C difficile infection in a duration-dependent fashion. Extended duration did not lead to additional SSI reduction.


Number needed to harm (NNH) is a concept that puts the issue in a perspective that often emphasizes the size effect of an intervention. The researchers found that the NNH for AKI after 24 to less than 48 hours, 48 to less than 72 hours, and 72 hours or more of postoperative prophylaxis were 9, 6, and 4, respectively. For C difficile infection the NNH were 2000, 90, and 50, respectively.


These results reinforce that stewardship efforts to limit duration of prophylaxis have the potential to reduce adverse events without increasing SSI.






Ban KA, Minei JP, Laronga C, et al. American College of Surgeons and Surgical Infection Society: Surgical Site Infection Guidelines, 2016 Update. J Amer Coll Surg 2017; 224(1): 59-74




Branch-Elliman W, O’Brien W, Strymish J, et al. Association of Duration and Type of Surgical Prophylaxis With Antimicrobial-Associated Adverse Events. JAMA Surg 2019; Published online April 24, 201






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