Delayed sternal closure (DSC) is a strategy used in cardiac surgery when immediate closure would compromise postoperative cardiovascular or respiratory stability, being performed in a second stage. However, DSC is associated with longer mechanical ventilation, prolonged ICU stay, and increased risk of healthcare-associated infections (HAIs) and surgical site infections (SSI), raising morbidity and mortality. Currently, no consolidated data or guidelines define the ideal antibiotic prophylaxis regimen and duration for these patients, resulting in wide variability in practice. This study aimed to evaluate monotherapy with cefuroxime until 24 hours after delayed sternal closure.

A retrospective before-and-after cohort study was conducted in a tertiary hospital in São Paulo. Pediatric patients undergoing DSC were included and divided into two groups: pre-intervention (n = 18; Jan/2022–Jun/2023) and post-intervention (n = 19; Jul/2023–Dec/2024). In the post-intervention group, antibiotic prophylaxis with cefuroxime was standardized until 24 hours post-DSC. Clinical and microbiological data were collected from medical records and the Hospital Infection Control Service (HICS). The primary outcome was SSI occurrence within 30 days (per ANVISA definition). Secondary outcomes included HAIs, hospital mortality, need for broad-spectrum antibiotic therapy, total antibiotic duration, and ICU stay length. Categorical variables were compared using Fisher’s exact test, and continuous variables using the Mann-Whitney U test (significance p < 0.05).

Cohorts were similar in age (7 [2–397] vs. 6 [2–190] days of life), female sex (33% vs. 31%), and complexity (STAT 4–5: 94% vs. 89%). No SSI cases were observed. HAIs occurred in 33% (6/18) of the pre-intervention group and 42% (8/19) of the post-intervention group (p = 1.0). Hospital mortality was 44% (8/18) vs. 47% (9/19) (p = 1.0). Cefuroxime duration was 4.0 [1–12] vs. 5.5 [1–13] days (p = 0.11), while empirical use of broad-spectrum antibiotics decreased (4 vs. 1 patient).

Maintaining cefuroxime until DSC proved safe, showing a similar profile to previously variable regimens and suggesting reduced need for broad-spectrum antibiotics. However, the small sample size and absence of SSI limit statistical analysis.