SAN DIEGO, CA—Do patients weighing more than 120kg need a preoperative dose of cefazolin 3g or does 2g suffice to prevent surgical site infections? That was the question addressed by investigators in a presentation at IDWeek 2015.

“Recent clinical practice guidelines for antimicrobial surgical prophylaxis recommend a more aggressive weight-based dosing scheme for obese patients scheduled to receive cefazolin,” Mary L. Staicu, PharmD, of Rochester General Hospital in Rochester, NY, noted. “Despite the lack of robust clinical efficacy data, we adopted these practice guidelines due to cefazolin’s favorable safety profile and relatively low cost.”

To evaluate the efficacy and safety of preoperatively administered cefazolin 2g vs. cefazolin 3g in this population, they performed a pre- and post-intervention retrospective analysis of 689 patients. A total of 373 patients had received cefazolin 2g between April and December 2012; following the surgical prophylaxis guideline update in April 2013, 316 patients received cefazolin 3g between April and December 2013.

Excluded were those who “did not receive perioperative cefazolin per national guidelines,” which included indication and timing of antibiotic administration, she reported.

Primary outcome was number of surgical site infections, as defined by the Centers for Disease Control and Prevention’s National Healthcare Safety Network. “Secondary outcomes included postoperative adverse drug reactions within 72 hours and number of Clostridium difficile infections within 3 months of receiving postoperative cefazolin,” they noted.

The two groups had similar baseline characteristics; however, those in the cefazolin 2g group weighed more (137.9kg vs. 135.3kg; P=0.031), underwent more urological procedures (22.5% vs. 13.9%; P=0.004), and had fewer cardiothoracic procedures (2.1% vs. 5.7%; P=0.043).

“Although the total weight tended to be slightly higher in the cefazolin 2g group, the two populations were well matched on BMI, age, and gender distribution, as well as procedure duration and invasiveness level,” she reported.

Results showed a trend toward lower rates of surgical site infections in the cefazolin 3g group, 1 per 100 cases, compared with 7 per 100 cases (1.9%) in the cefazolin 2g arm (P=0.076). Similarly, no significant differences were observed in the number of cases of Clostridium difficile infections (0 vs. 2; P=0.210) or documented total adverse reactions (17.2% vs. 18.0%; P=0.764). The most common adverse reaction was gastrointestinal, in 11% of patients.

“Additional prospectively designed, nonrandomized clinical studies are needed to further evaluate the clinical efficacy of this intervention in larger patient groups,” she concluded.