Intraoperative Particulate Matter Exposure and Surgical Site Infection Risk in Cardiac Surgery: A Prospective Feasibility Study

Authors:
Oluwaseun Adeyemi, Divya Kewalramani, Justin Benton, Gediminas Mainelis, Philip Barie, Mayur Narayan

Body of Abstract:
Despite decades of investment in operating room ventilation systems, surgical site infections (SSIs) remain a major source of morbidity in clean cardiac procedures. While bacterial contamination of surgical wounds correlates with airborne particle concentrations, the relationship between quantified intraoperative particulate matter (PM) exposure and clinical SSI development remains uncharacterized. We hypothesized that patients who develop SSI following cardiac surgery encounter higher proportions of high-risk PM thresholds compared to patients without SSI, with phase-specific exposure patterns distinguishing infected from non-infected cases.

Methods: We prospectively enrolled 31 CABG patients with continuous intraoperative PM monitoring and 30-day SSI surveillance. PM was quantified by number concentration (NC: 0.3–0.5, 0.5–1.0, 1.0–2.5 µm) and mass (PM1.0, PM2.5). Operative phases were baseline (procedure start to cardiopulmonary bypass [CPB] initiation), prolonged electrocautery (CPB period), and closure (CPB termination to procedure end). High-risk PM exposure was defined as ≥2 standard deviations above baseline mean. We calculated the proportion of each phase exceeding high-risk thresholds and compared exposure patterns between SSI and non-SSI cohorts.

Results: Among 31 enrolled patients (mean age 65.5 ± 9.7 years, 90.3% male, mean BMI 29.1 ± 5.2 kg/m²), one patient (3.2%) developed deep sternal wound SSI requiring surgical debridement and prolonged antibiotic therapy. Median operative duration was 4.2 hours (IQR 3.8–4.9), with baseline, electrocautery, and closure phases comprising 18%, 64%, and 18% of total operative time, respectively. During the closure phase, the SSI case exhibited elevated PM exposure across all size fractions compared to non-SSI patients: PM2.5 exceeded high-risk thresholds for 8.3% versus 0.3% of phase duration (27.7-fold difference), PM1.0 for 8.0% versus 0.3% (26.7-fold), NC1.0–2.5 for 1.4% versus 0.1% (14-fold), NC0.5–1.0 for 8.3% versus 0.6% (13.8-fold), and NC0.3–0.5 for 8.3% versus 0.01% (830-fold). Mass-based PM metrics demonstrated more pronounced divergence than number concentrations, with PM2.5 and PM1.0 showing the largest absolute differences. During the prolonged electrocautery phase, the SSI case exhibited elevated exposure primarily in fine particle fractions: NC0.5–1.0 exceeded thresholds for 2.9% versus 0.2% of phase duration (14.5-fold difference) and NC0.3–0.5 for 3.0% versus 0.2% (15-fold). Temporal analysis revealed that 89% of high-risk PM excursions during closure occurred within 15 minutes preceding final skin approximation

Conclusion: This preliminary evidence demonstrates phase-specific PM exposure patterns distinguishing SSI from non-SSI cases, with closure phase exhibiting the strongest divergence. These findings establish technical feasibility for continuous, size-resolved PM monitoring and justify larger prospective studies examining PM exposure thresholds as modifiable SSI risk factors.