Multicenter Evaluation of Predictors for Pseudomonas aeruginosa Surgical Site Infections after Head/Neck Cancer Microvascular Free-Flap Reconstruction

Background: Surgical site infections (SSI) in head/neck cancer patients who undergo microvascular free-flap reconstruction (FFR) are associated with poor outcomes. Post-operative antibiotic prophylaxis (POABP) varies across institutions and specific patient populations. The role of Pseudomonas aeruginosa (PSA) SSI in this population has not been well established, but perceived PSA risk factors are extrapolated from traditional variables found in other disease states (e.g. immunosuppression, diabetes). Therefore, some clinicians prefer to use antipseudomonal POABP in this setting. The objective of this study was to characterize SSI microbiology and identify PSA risk factors in FFR among seven American institutions.

Methods: Multicenter case-case-control study included hospitalized patients who underwent head/neck cancer FFR from 1/08-12/14. Cases were defined as those with PSA SSI; controls were defined as patients with non-PSA SSI and those without SSI. Unique patients with PSA SSI were compared to those with non-PSA SSI and to un-infected controls.

Results: 679 patients included: 11 PSA SSI, 86 non-PSA SSI, 582 uninfected controls. 82% of patients were ASA class III or higher (82%). POABP spectrum: Gram-positives with enteric Gram-negatives (60%), Gram-positives with anti-pseudomonal agent (26%), Gram-positive only (13%). Median duration of any POABP was 6 days (IQR: 3-8). 107 organisms were obtained from 54 (56%) of all patients SSI, 34 (29%) were polymicrobial. Among non-PSA SSI, cultured organisms were: Gram-positives 49 (46%), other enteric Gram-negatives 23 (21%), anaerobes 2 (2%), other 22 (21%). Patients with PSA SSI were more likely to require emergent operating room return (P=0.042). Bivariate predictors for developing PSA SSI were reconstruction of external facial skin defect and use of latissimus dorsi as a free-flap (Table 1).

Conclusion: PSA was an uncommon SSI organism following FFR. POABP spectrum and other traditional risk factors were not associated with PSA SSI. More systematic approaches to SSI prevention should be explored in this high-risk population.