Duration of prophylaxis

Because of the long duration of many cardiac procedures, repeat intraoperative doses are often necessary. Administer a repeat dose if:

• after prophylaxis is given, there is a significant delay in starting the operation
• cefazolin is used and more than 3 to 4 hours (ie more than two cefazolin half-lives) have elapsed since the previous dose
• there is excessive blood loss during the procedure (eg in adults, 1.5 litres or more).

Data from low-quality studies suggest that postoperative doses of prophylaxis reduce the risk of postoperative infections following cardiac procedures. While postoperative doses may be considered, prophylaxis should not continue beyond 24 hours, even in the presence of chest drains. Extended prophylaxis is associated with an increased risk of adverse effects, including subsequent infection with resistant pathogens and Clostridioides difficile.

The optimal duration of prophylaxis for cardiac transplant procedures in which the chest is not primarily closed or the patient has a chronically infected ventricular assist device is unclear—seek expert advice.

When measuring the time to a repeat intraoperative or postoperative dose, measure the interval from the time of the previous dose rather than the beginning of the operation. See Suggested intraoperative redosing intervals for antibiotics commonly used for surgical antibiotic prophylaxis for redosing intervals for the antimicrobials recommended above.