Characterizing Early-Onset Surgical Site Infection after Lower Extremity Bypass Surgery

Abstract

Surgical site infections (SSI) are the most common complication following lower extremity bypass (LEB) surgery. SSIs contribute to significant patient morbidity and healthcare expenditure, and accurate detection of SSIs remains an important step in reduction efforts. In this study, we aimed to characterize early-onset SSIs among patients undergoing LEB surgery. Institutional medical records were retrospectively queried for all LEB operations performed across three hospitals from 2018-2022. All SSIs within a 90-day postoperative period were included, per CDC definition, and categorized as early- (within seven days of operation), standard- (8-30 days), or delayed-onset (31-90 days). The Southampton grading scale was used to stratify the severity of infection (grade 2, erythema; grade 3, erythema with serous drainage; grade 4; erythema with purulent drainage; or grade 5, severe wound necrosis). Data were analyzed using univariate tests and logistic regression analysis. A total of 517 LEB operations were performed over the five-year study period. Median follow-up period was 18.5 months. Early-, standard-, and delayed-onset SSIs were diagnosed in 2.9% (n=15), 15.1% (n=78), and 4.6% (n=24) of patients, respectively. Compared with standard- and delayed-onset groups, patients with early-onset SSIs were more frequently non-smokers (26.7% vs 3.9% vs 8.3%, p=0.03) and had lower prevalence of comorbidities. Early-onset SSIs most frequently presented as Southampton grade 2 (60.0%) or grade 5 (20.0%) infections; whereas standard- and delayed-onset SSIs were more evenly distributed among grade 2 (30.4%), grade 3 (41.2%), and grade 4 (21.6%) presentations (p=0.002). The most commonly isolated organisms among the early-onset SSI group were Gram-negative rods (20.0%). In comparison, polymicrobial infections (19.6%) and Gram-positive cocci (14.7%) were most common among standard- and delayed-onset groups (p=0.04). The early-onset SSI group experienced a longer index hospitalization (11 vs 6 vs 8 days, p=0.02) and lower 30-day readmission rates (13.3% vs 59.0% vs 45.8%, p=0.005) compared with standard- and delayed-onset groups. On multivariate analysis, active smoking (hazard ratio [HR] 0.15, 95% confidence interval [CI], 0.02-0.98, p=0.035), former smoking (HR 0.08, 95% CI, 0.01-0.71, p=0.02), coronary artery disease (HR 0.15, 95% CI, 0.03-0.83, p=0.03), and hypertension (HR 0.13, 95% CI, 0.03-0.68, p=0.02) were associated with a lower risk of early-onset infection, when compared with patients suffering standard- and delayed-onset SSIs. Early-onset SSIs after LEB surgery have a distinct clinical presentation, impact healthier patients, and are associated with more virulent organisms compared with standard- and delayed-onset SSIs.