23 Duration of surgical antibiotic prophylaxis after cardiac surgery: 24 hours is sufficient

Aim Up to 48 h post-operation prophylaxis is recommended following cardiac surgery. We analysed the surgical site infection (SSI) rates following 24- or 48-h prophylaxis to see if 24 h was inferior to 48-h duration. Method We analysed the SSI rates following adult cardiac surgery procedures from the prospective Health Quality and Safety Commission’s (HQSC) national Surgical Site Infection Improvement Programme (SSIIP)1,2. Procedures from January 2014 to June 2023 were included. One cardiac surgical unit used 24-h prophylaxis and the four other units used 48-h prophylaxis. We compared patient demographics and SSI outcome for the 24- and 48-h groups. Patients were followed for 90-days after surgery and USA CDC NHSN SSI definitions were applied. Uni- and multivariable analysis were performed. Results There were 17 227 cardiac procedures; 63% were coronary artery bypass graft (CABG) procedures and 37% other procedures (CARD), for example valve replacement. 99.6% were clean procedures and cefazolin was the prophylactic antibiotic for 97.3% of operations. There was no difference in the SSI rates for cefazolin versus other agents (P = 0.61). After multivariable analysis overall independent risk factors for SSI were female sex (odds ratio 1.6), obesity (OR for BMI 30–<35 = 2.0, 35–<40 = 3.0, BMI > 40 = 3.8), type of procedure CABG OR 2.8 versus CARD, and diabetes (OR 1.6). SSI rates were not higher following 24-h prophylaxis, Table:TableCardiac surgical site infection rates for 24- verses 48-hour post-operation prophylaxisDuration of post-op prophylaxisType of SSI*24 hN = 7,80848 hN = 9,419Odds ratio (95% c.i.)P valueAny site and type3.9%3.6%1.1 (0.9–1.3)0.35Chest only2.2%2.1%1.1 (0.9–1.3)0.54Chest: deep and organ space1.3%1.2%1.1 (0.9–1.5)0.43*After multivariable analysis for the types of SSI, diabetes (ORs 1.9–2.1) and Māori ethnicity (ORs 1.4–1.9) were the only consistent independent risk factors for each SSI group type. Conclusion There was no difference in the SSI rates following 24- or 48-h post-operation prophylaxis. This suggests that 24-h prophylaxis is sufficient following cardiac surgery.