Impact of Intra-Operative Adverse Events on the Risk of Surgical Site Infection in Abdominal Surgery

BACKGROUND: Intra-operative adverse events (iAEs) recently were shown to correlate independently with an increased risk of post-operative death, morbidity, re-admissions, and length of hospital stay. We sought to understand further the impact of iAEs on surgical site infections (SSIs) in abdominal surgical procedures and delineate which patient populations are most affected. We hypothesized that all patients with iAEs have an increased risk for SSI, especially those with pre-existing risk factors for SSI. PATIENTS AND METHODS: To identify iAEs, a well-described three-step methodology was used: (1) the 2007-2012 American College of Surgeons-National Surgical Quality Improvement Program database was merged with the administrative database of our tertiary academic center, (2) the merged database was screened for iAEs in abdominal surgical procedures using the International Classification of Diseases, Ninth Revision, Clinical Modification-based Patient Safety Indicator "Accidental Puncture/Laceration," and (3) each flagged record was systematically reviewed to confirm iAE occurrence. Uni-variable and backward stepwise multi-variable analyses (adjusting for demographics, co-morbidities, type and complexity of operation) were performed to study the independent correlation between iAEs and SSIs (superficial, deep incisional, and organ-space). The correlation between iAEs and SSIs was investigated especially in patients deemed a priori at high risk for SSIs, specifically those older than age 60 and those with diabetes mellitus, obesity, cigarette smoking, steroid use, or American Society of Anesthesiologists class ≥III. RESULTS: A total of 9,288 operations were included, and iAEs were detected in 183 (2.0%). Most iAEs consisted of bowel (44%) or vessel (29%) injuries and were addressed intra-operatively (92%). SSI occurred in 686 (7.4%) cases and included 331 (3.5%) superficial, 32 (0.34%) deep incisional, and 333 (3.6%) organ/space infections. iAEs were correlated independently with SSI (odds ratio [OR] = 1.67; 95% confidence interval [CI], 1.11-2.52, p = 0.013), and more severe iAEs were associated with a higher risk of infection. Analysis by SSI type revealed a significant association with organ/space SSI (OR = 1.81, 95% CI 1.07-3.05; p = 0.027), but not incisional infections. Most interestingly, the occurrence of an iAE was correlated with increased SSI rate in the low-risk but not the high-risk patient populations. Specifically, iAEs increased SSI in patients younger than 60 (OR = 2.69, 95% CI 1.55-4.67, p < 0.001), non-diabetic patients (OR = 1.64, 95% CI 1.04-2.58, p = 0.034), non-obese patients (OR = 2.9, 95% CI 1.81-4.66, p < 0.001), non-smokers (OR = 1.67, 95% CI 1.08-2.6, p = 0.022), with no steroid use (OR = 1.73, 95% CI 1.15-2.6, p < 0.008), and with ASA class <III (OR = 2.26, 95% CI 1.31-3.87, p = 0.003). CONCLUSIONS: The iAEs are associated independently with increased SSIs, particularly in patients with less pre-existing risk factors for SSI. Preventing iAEs or mitigating their impact, once they occur, may help decrease the rate of SSIs.