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Study: Contamination increases with longer duration for procedures done with laminar airflow
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In this prospective observational study, there were 37% fewer colony forming units in operating rooms where laminar airflow was used during 81 orthopedic procedures than in the same operating room outside of the laminar airflow area.
The findings were based on bacteria collected from special surface testing plates placed inside the operating room (OR), one each per room within the laminar air flow area and outside of that area. Investigators also factored in data for the number of OR door openings per case. They used samples taken from testing plates placed in sterile ORs with no door openings as controls.
Eric B. Smith, MD, and colleagues, who conducted the study during 2 months in 2011, noted that case duration was a variable, with 72% of the cases being completed within 90 minutes; 28 cases and 24 cases lasted 60 minutes and 90 minutes, respectively. They used a specific statistical model, which is required for colony forming unit (CFU) counts. The team also developed a full model to assess all the cumulative variables, including which of three ORs included in the study was used, the duration of surgery, the number of people in the OR, door openings, and the presence of laminar airflow.
"The contamination rate is consistently lower inside than outside the laminar airflow," Smith and colleagues wrote in the study. "The plot of contamination rate vs. time suggests that laminar airflow is protective against microbial contamination for surgeries lasting 90 minutes or less."
Based on an analysis of 30-minute intervals during the surgeries, the average cumulative number of times door openings occurred in the OR increased the longer the procedure lasted. This ranged from 17 openings at 30 minutes to 106 opening at 180 minutes. The bulk of the contamination risk came with the first opening of the OR door, Smith and colleagues reported.
"Protocols need to be developed and implemented to reduce OR door openings within the first 90 minutes of surgery," they wrote in the study.
Disclosure: This study was funded by a grant from the Sharpe-Strumia Foundation.
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