The impact of prophylactic antibiotic duration on postoperative outcomes post-cardiothoracic surgery: a retrospective cohort study

Surgical site infections (SSIs) are a significant complication following cardiac surgery, increasing patient morbidity and mortality. While prophylactic antibiotics reduce infection rates, the optimal duration of prophylaxis remains unclear. This study aimed to evaluate how the duration of antimicrobial prophylaxis affects the incidence of surgical site infections in patients undergoing cardiothoracic surgery. We conducted a retrospective cohort study at King Faisal Specialist Hospital and Research Center in Riyadh and Jeddah between May 2023 and August 2024. We included adult patients (≥ 18 years) who underwent Cardiothoracic Surgery and received postoperative prophylactic antibiotics for at least 24 h. We excluded patients with pre-existing infections or those treated with antibiotics within 48 h before surgery. The primary outcome was the incidence of surgical site infections within 90 days post-surgery. Secondary outcomes included infection type, mortality, antimicrobial resistance, and hospital and ICU length of stay (LOS). We included 435 patients, with 216 receiving antibiotic prophylaxis for > 48 h and 219 for ≤ 48 h. The mean age was 53.5 ± 14.5 years, and 67% were male. Surgical site infections within 90 days were significantly more frequent in the > 48-hour group (10.6% vs. 3.2%, p = 0.002). In the multivariable model ( n = 435; 30 SSI events), prophylaxis > 48 h was associated with higher odds of SSI after adjustment for age, diabetes, any CABG procedure (conventional or robotic), and operative duration (adjusted odds ratio [aOR], 3.09; 95% CI, 1.22–7.84; p = 0.017). The prolonged-prophylaxis group had a higher frequency of antibiotic resistance (7.9% vs. 3.2%; Fisher exact p = 0.037). Mortality did not differ significantly between groups ( p = 0.782). Prolonged antibiotic prophylaxis (> 48 h) after cardiothoracic surgery was associated with higher rates of surgical site infections and increased antibiotic resistance. Not applicable.