Adding vancomycin to cefazolin didn't reduce infections among arthroplasty patients

Adding vancomycin to cefazolin did not prevent surgical-site infections among patients without known methicillin-resistant Staphylococcus aureus (MRSA) who underwent knee, hip, or shoulder arthroplasty, new study results show.

To test the efficacy of adding vancomycin as a surgical prophylaxis, investigators carried out the Australian Surgical Antibiotic Prophylaxis trial in 11 hospitals throughout the country. Trial participants received 2 g of cefazolin within the hour preceding surgery and were randomized to either vancomycin or placebo within two hours prior to incision. Investigators chose to administer 1.5 g of vancomycin as it “aligned with the recommended weight-based dose for most trial patients,” they said. Findings were published in The New England Journal of Medicine on Oct. 19.

The primary outcome of surgical-site infection rates within 90 days of the procedures occurred in 91 (4.5%) of the 2,044 patients who received 1.5 g of vancomycin and cefazolin versus 72 (3.5%) of the 2,069 patients who received a saline placebo plus cefazolin, a relative risk (RR) of 1.28 (95% CI, 0.94 to 1.73; P=0.11). Infections occurred in 5.7% of knee surgery patients who received the intervention compared with 3.7% of controls (RR, 1.52; 95% CI, 1.04 to 2.23). Three percent of hip surgery patients who were administered vancomycin got infections compared with 3.1% of controls (RR, 0.98; 95% CI, 0.59 to 1.63). No patients undergoing shoulder surgery who received vancomycin got infections, while one patient in the control group did.

Most infections that occurred in the trial were superficial, and methicillin-susceptible S. aureus was the most commonly detected infection. Adverse events, including hypersensitivity reactions and acute kidney injury, occurred in 1.7% of both groups. “The results of subgroup analyses suggested a possible increased risk of surgical-site infection in knee arthroplasty with the addition of vancomycin on secondary analysis,” researchers wrote. “Vancomycin prophylaxis was associated with an increased risk of hypersensitivity reactions and a decreased risk of acute kidney injury,” they said.

The study authors cautioned that the results may not be generalizable to those with a known infection or colonization with MRSA but they concluded that “the addition of vancomycin to cefazolin prophylaxis was not superior to placebo for the prevention of surgical-site infections in arthroplasty among patients without known MRSA colonization.”