Breaking the Silence: Study highlights Hidden Burden of Surgical Site Infections in Cardiac Surgery

In the operating room (OR), key contributors to microbial contamination include inadequate microbial sterilization, airflow issues, and surface contamination. Specifically, in cardiac surgeries, it has been identified that air is the primary source of bacterial contamination, with approximately one-third of bacteria potentially entering the surgical incision directly from the air. To assess the microbial air quality in cardiac ORs, recently published study compared two methodologies: conventional settle plate techniques and an air sampling device. Airborne microbial contamination was measured using a 9 cm diameter Petri dish containing Muller Hinton's Agar, exposing it to air for one hour to assess total viable count (TVC) expressed in colony-forming units per cubic meter (CFU/m³). Passive sampling involved placing the Petri dish at specific distances from walls and floors, while active sampling utilized a Surface Air System (SAS) air sampler with a constant flow rate.

Results of Air Quality Assessment

Results indicated notable differences in CFU counts, with microbiological air pollution levels ranging between 50 to 500 CFU/m³ in conventional ventilation systems, compared to fewer than 20 CFU/m³ in ultra-clean air settings. The permissible bioload in an empty conventional OR should be below 10 CFU/m³, and the count during surgical procedures should not exceed 180 CFU/m³. Data analysis suggested strong correlations between the two sampling techniques during certain surgical time frames, highlighting that adult cardiac ORs had a significantly higher bioload than pediatric ORs, potentially due to longer operation times and higher staff presence.

Importance of Continuous Microbiological Surveillance

The findings underscore the importance of continuous microbiological surveillance in cardiac ORs to maintain air quality and minimize SSI risks. Although settle plate methods are cost-effective and straightforward, their limitations include a tendency to capture only larger particles influenced by gravity. On the other hand, air sampling devices can actively collect a broader range of particles, thus providing a more comprehensive assessment of airborne contamination.

Challenges and Future Directions in Air Quality Monitoring

Despite the advantages, challenges remain, including the lack of standardized guidelines for air sampling techniques and thresholds for permissible contaminant levels in ORs. The implementation of air sampling devices may enhance monitoring of air quality, which could reduce postoperative infection complications. Further research is necessary to establish reliable protocols and standards, underscoring the critical need for effective infection control practices in cardiac surgical settings.

Key Points

- Surgical site infections (SSIs) in cardiac surgery have incidence rates between 0.25% to 4% and can lead to a mortality rate as high as 30%, significantly affecting patient health and increasing healthcare costs along with hospitalization duration risks that can elevate mortality rates up to 11 times compared to other surgical procedures.

- Risk factors for SSIs are categorized into three groups: preoperative (e.g., diabetes, obesity), perioperative (e.g., surgical environment and practices), and postoperative (e.g., wound care and recovery processes), indicating a multi-faceted nature of infection risks.

- Inadequate microbial sterilization, airflow issues, and surface contamination are highlighted as primary contributors to microbial contamination in the operating room, with air identified as a major source of bacterial contamination that can directly enter surgical incisions.

- A study comparing settle plate techniques and air sampling devices for measuring airborne microbial contamination found that conventional ventilation systems averaged between 50 to 500 CFU/m³, while ultra-clean air settings recorded fewer than 20 CFU/m³, emphasizing the need for certain bioload thresholds in surgical environments.

- Continuous microbiological surveillance in cardiac operating rooms is crucial to maintaining air quality and minimizing SSI risks. Settle plate methods, while cost-effective, have limitations, whereas air sampling devices provide a more comprehensive analysis of airborne contamination.

- There are ongoing challenges in establishing standardized guidelines and thresholds for permissible contaminant levels in operating rooms. Adoption of air sampling devices could improve air quality monitoring, but further research is required to develop reliable protocols and enhance infection control measures in cardiac surgery settings.

Reference –

Alok Kumar et al. (2025). Microbiological Surveillance Of Air Quality In Cardiac Operation Theatres: Comparison Of The Conventional Settle Plate Technique Vs Use Of An Air Sampling Device. *Annals Of Cardiac Anaesthesia*, 28, 156 - 160. https://doi.org/10.4103/aca.aca_200_24.