Surgical site infection: Prophylaxis

Perioperative antibiotics aimed at preventing surgical site infection should be administered intravenously within 60 minutes before incision; studies have shown that this is the interval in which the risk of surgical site infection is lowest. For antibiotics that require slower/longer infusions, such as fluoroquinolones or vancomycin, 120 minutes is appropriate. Some studies indicate that antibiotic prophylaxis within 30 minutes of incision is even more effective at lowering the risk of surgical site infection. Giving antibiotics after incision does not allow time for the antibiotic to reach minimum inhibitory concentration in the patient’s circulation and has been shown to result in a significantly higher rate of surgical site infection. However there is no strong evidence that antibiotics given within 15 minutes is associated with a higher risk of infection due to the design of studies that are published in the literature. Surgical site infection prophylaxis should last no longer than 24 hours in duration, for noncardiac cases.

Cefazolin covers most gram-positive organisms and is the therapy of choice for procedures that do not infiltrate contaminated organs. If the patient has a low-risk allergy to penicillin, a trial of cephalosporin may be appropriate. Note that patients with true IgE-mediated allergy to penicillin have a higher risk of being allergic to other drugs. In the case that cephalosporin is high risk or contraindicated, most experts agree that using vancomycin and clindamycin is an appropriate substitute.

Patients with obesity or morbid obesity have been found to have lower concentrations of drug as compared to patients receiving the same dose of antibiotic who are not obese. This is thought to be due to increased fat content affecting metabolism and clearance related to drug lipophilicity. This is also why some institutions have adopted the practice to give all adult patients a minimum dose of 2 g cefazolin in lieu of 1 g for patients under 80 kg. Pediatric patients should receive weight-based dosing.