Door openings in the operating room are associated with increased environmental contamination

Abstract

•Door openings are correlated with bacterial contamination in the operating room.•Vertical laminar airflow (LAF) reduces the negative effects of door openings.•Number of staff was still associated with increased contamination under LAF. Door openings in the operating room (OR) have been hypothesized to increase OR environmental contamination. This study measured average colony-forming units (CFU) in the OR as a function of door openings and other potentially important variables. Bacterial settle plates were placed inside and outside of laminar airflow (LAF) by both exit doors, on the instrument table, and on the back instrument table (if applicable) for 48 orthopedic and general surgery procedures. CFU data were paired to Staphylococcus aureus colonization status, door openings, surgery duration, time of day, OR location, number of staff, use of warming devices, temperature, and humidity. The number of door openings in the OR and surgery duration were significantly associated with increased CFU in the OR overall and outside of LAF. However, under LAF conditions, only the number of OR personnel was significantly associated with increased CFU. Door openings in the operating room (OR) have been hypothesized to increase OR environmental contamination. This study measured average colony-forming units (CFU) in the OR as a function of door openings and other potentially important variables. Bacterial settle plates were placed inside and outside of laminar airflow (LAF) by both exit doors, on the instrument table, and on the back instrument table (if applicable) for 48 orthopedic and general surgery procedures. CFU data were paired to Staphylococcus aureus colonization status, door openings, surgery duration, time of day, OR location, number of staff, use of warming devices, temperature, and humidity. The number of door openings in the OR and surgery duration were significantly associated with increased CFU in the OR overall and outside of LAF. However, under LAF conditions, only the number of OR personnel was significantly associated with increased CFU. Surgical site infections (SSIs) dramatically increase length of hospital stay, hospital costs, and patient morbidity after surgery.1Magill S.S. Edwards J.R. Bamberg W. Beldavs Z.G. Dumyati G. Kainer M.A. et al.Multistate point-prevalence survey of health care-associated infections.N Engl J Med. 2014; 370: 1198-1208Crossref PubMed Scopus (2458) Google Scholar Most SSIs originate from endogenous patient flora and are presumed to be a result of inoculation of the operative site at the time of the surgery.2Perl T.M. Cullen J.J. Wenzel R.P. Zimmerman M.B. Pfaller M.A. Sheppard D. et al.Intranasal mupirocin to prevent postoperative Staphylococcus aureus infections.N Engl J Med. 2002; 346: 1871-1877Crossref PubMed Scopus (634) Google Scholar, 3Bode L.G. Kluytmans J.A. Wertheim H.F. Bogaers D. Vandenbroucke-Grauls C. Roosendaal R. et al.Preventing surgical-site infections in nasal carriers of Staphylococcus aureus.N Engl J Med. 2010; 362: 9-17Crossref PubMed Scopus (892) Google Scholar In a minority of cases, contamination of the operating room (OR) environment has been documented as an important source of SSI, often only identified in the setting of a cluster or outbreak.4Lutz B.D. Jin J. Rinaldi M.G. Wickes B.L. Huycke M.M. Outbreak of invasive Aspergillus infection in surgical patients, associated with a contaminated air-handling system.Clin Infect Dis. 2003; 37: 786-793Crossref PubMed Scopus (87) Google Scholar Laminar airflow (LAF) has been shown to decrease bacterial colony-forming units (CFU) around the operating field5Smith E.B. Raphael I.J. Maltenfort M.G. Honsawek S. Dolan K. Younkins E.A. The effect of laminar air flow and door openings on operating room contamination.J Arthroplasty. 2013; 28: 1482-1485Abstract Full Text Full Text PDF PubMed Scopus (87) Google Scholar, 6Erichsen Andersson A. Petzold M. Bergh I. Karlsson J. Eriksson B.I. Nilsson K. Comparison between mixed and laminar airflow systems in operating rooms and the influence of human factors: experiences from a Swedish orthopedic center.Am J Infect Control. 2014; 42: 665-669Abstract Full Text Full Text PDF PubMed Scopus (61) Google Scholar and is used by some institutions to prevent SSIs, although the benefit of LAF is controversial.7Gastmeier P. Breier A.C. Brandt C. Influence of laminar airflow on prosthetic joint infections: a systematic review.J Hosp Infect. 2012; 81: 73-78Abstract Full Text Full Text PDF PubMed Scopus (120) Google Scholar Mixed results regarding the benefits of LAF may result from compromised function of the airflow system in the setting of excessive door openings and OR traffic.5Smith E.B. Raphael I.J. Maltenfort M.G. Honsawek S. Dolan K. Younkins E.A. The effect of laminar air flow and door openings on operating room contamination.J Arthroplasty. 2013; 28: 1482-1485Abstract Full Text Full Text PDF PubMed Scopus (87) Google Scholar, 8Pokrywka M. Byers K. Traffic in the operating room: a review of factors influencing air flow and surgical wound contamination.Infect Disord Drug Targets. 2013; 13: 156-161Crossref PubMed Scopus (22) Google Scholar, 9Andersson A.E. Bergh I. Karlsson J. Eriksson B.I. Nilsson K. Traffic flow in the operating room: an explorative and descriptive study on air quality during orthopedic trauma implant surgery.Am J Infect Control. 2012; 40: 750-755Abstract Full Text Full Text PDF PubMed Scopus (170) Google Scholar In a study of exclusively orthopedic procedures, the number of door openings per case ranged from 0 to 66, with an average of 17.4 door openings per case.6Erichsen Andersson A. Petzold M. Bergh I. Karlsson J. Eriksson B.I. Nilsson K. Comparison between mixed and laminar airflow systems in operating rooms and the influence of human factors: experiences from a Swedish orthopedic center.Am J Infect Control. 2014; 42: 665-669Abstract Full Text Full Text PDF PubMed Scopus (61) Google Scholar A different orthopedic group reported an average of 60 door openings per case (0.64 door openings per minute) for primary arthroplasty procedures, and an average of 135 door openings per case in revision arthroplasty (0.84 door openings per minute).10Panahi P. Stroh M. Casper D.S. Parvizi J. Austin M.S. Operating room traffic is a major concern during total joint arthroplasty.Clin Orthop Relat Res. 2012; 470: 2690-2694Crossref PubMed Scopus (121) Google Scholar In this study, we measured environmental contamination in the OR as a function of door openings, LAF, and other variables. Bacterial settle plates (Remel; Lenexa, Kansas) were placed inside and outside of LAF by exit doors, on the instrument table, and on the back instrument table (if applicable) for 48 orthopedic and general surgery procedures over a 6-week period. Different plates were used for the period of time from surgical kit opening until incision and from incision to closure. CFU were counted on each plate by trained microbiologists who were blinded to all other aspects of the study, and average CFU per plate were measured. The patient's Staphylococcus aureus colonization status, surgery duration, time of day, OR location, number of staff, use of Bair Hugger warming devices, temperature, and humidity were measured for each case from hospital databases. Number of door openings was manually counted by research personnel. In all cases, OR personnel were not blinded to participation in the study and were aware that door openings were being counted during these surgical cases. All ORs use a vertical LAF system (BioAir Systems; Greensboro, North Carolina), which uses a combination of outside and return air through HEPA filters. The HEPA filters are replaced every 3 years. These LAF units are connected to a heating, ventilation, and air conditioning (HVAC) system that is dedicated to the hospital's ORs. This HVAC system has pre-filters that are replaced quarterly and final filters that are replaced annually. ORs are maintained at 65°F and are humidity controlled. SSIs were evaluated by prospective infection control surveillance according to National Healthcare Safety Network recommendations. Binary variables were analyzed using the Wilcoxon 2-sample test. Continuous variables were analyzed using univariate linear regression; for ease of presentation, they were also divided into strata to demonstrate changes in mean and range (Table 1). Multivariable regression analysis was not performed because the variables that were significant on univariate analysis (surgery duration, number of door openings, and number of staff) demonstrated collinear coefficients ≥ 0.3. Statistical tests and figures were generated using SAS software (version 9.3; SAS, Cary, North Carolina). The hospital's institutional review board approved this study.Table 1Average colony-forming units (CFU) for studied variablesVariableTotalP-valueOutside LAFP-valueInside LAFP-valueMean CFU (range)Mean CFU (range)Mean CFU (range)Time of day Morning2.63 (0.00 – 13.6).453.81 (0.00 – 15.0).410.98 (0.00 – 12.0).52 Afternoon1.69 (0.33 – 4.38)2.56 (0.00 – 7.00)0.75 (0.00 – 1.50)Operating room location New pod3.45 (0.75 – 8.6).245.50 (1.50 – 15.0).300.81 (0.00 – 2.50).73 Old pod2.28 (0.00 -13.6)3.23 (0.00 – 9.50)0.96 (0.00 – 12.0)Number of staff*Analysis by univariate linear regression. 5-61.35 (0.00 – 4.33).091.80 (0.00 – 5.50).350.50 (0.00 – 2.00).03 7-82.17 (0.25 – 8.57)3.52 (0.00 – 15.0)0.60 (0.00 – 2.50) 9-102.19 (0.25 – 5.13)3.96 (0.50 – 9.00)0.96 (0.00 – 2.50) 11-124.26 (0.50 – 13.3)4.67 (1.00 – 9.00)2.58 (0.00 – 12.0)Time frame†Differentiation between case setup and surgery was only performed for plates inside LAF; operating room temperature and humidity were within normal range for all procedures; and warming blankets were used for all procedures. Case setup--0.54 (0.00 – 2.50).02 Surgery--0.41 (0.00 – 9.50)Duration*Analysis by univariate linear regression. <140 min2.13 (0.00 – 13.3).092.60 (0.00 – 9.00).00161.06 (0.00 – 12.0).92 >140 min2.82 (0.50 – 5.75)4.60 (1.00 – 15.0)0.81 (0.00 – 2.50)Door openings*Analysis by univariate linear regression. 20-391.52 (0.00 – 4.38).032.20 (0.00 – 7.00).00120.50 (0.00 – 2.00).73 40-592.62 (0.25 – 13.3)3.26 (0.50 – 9.50)1.27 (0.00 – 12.0) 60-792.86 (0.50 – 8.57)4.78 (1.00 – 15.0)0.39 (0.00 – 2.00) 80 +3.65 (0.88 – 5.88)5.93 (1.50 – 9.50)1.29 (0.50 – 2.50)Door openings/min*Analysis by univariate linear regression. 0.20-0.291.85 (0.00 – 4.38).152.85 (0.00 – 7.00).310.65 (0.00 – 2.50).20 0.30-0.391.95 (0.25 – 5.75)3.05 (0.00 – 9.50)0.66 (0.00 – 2.00) 0.40-0.493.29 (0.33 – 8.57)5.08 (0.00 – 15.0)0.92 (0.00 – 2.50) ≥ 0.503.38 (0.50 – 13.3)3.64 (1.00 – 9.00)2.14 (0.00 – 12.0)Colonization status MSSA‡MSSA: methicillin-sensitive Staphylococcus aureus. Colonization status only available for inpatient surgery. No patients were colonized with methicillin-resistant Staphylococcus aureus.2.13 (1.50 – 3.25).704.60 (3.00 – 6.50).860.80 (0.00 – 2.50).78 No MSSA1.88 (0.25 – 3.67)4.44 (0.00 – 9.50)0.94 (0.00 – 2.50)All analyses used the 2-sided Wilcoxon 2-sample test unless otherwise specified. CFU, colony-forming units; LAF, laminar airflow.* Analysis by univariate linear regression.† Differentiation between case setup and surgery was only performed for plates inside LAF; operating room temperature and humidity were within normal range for all procedures; and warming blankets were used for all procedures.‡ MSSA: methicillin-sensitive Staphylococcus aureus. Colonization status only available for inpatient surgery. No patients were colonized with methicillin-resistant Staphylococcus aureus. Open table in a new tab All analyses used the 2-sided Wilcoxon 2-sample test unless otherwise specified. CFU, colony-forming units; LAF, laminar airflow. Forty-eight procedures were observed (24 arthroplasty, 7 arthroscopy, 6 podiatry, 5 spine, 4 general surgery, and 2 arthroscopic tendon repair). An average of 54 door openings (range, 21-122) per case were observed, or 0.38 (range, 0.21-0.61) door openings per minute. Door opening times ranged from 6 to 16.5 seconds for manual doors and 18-20 seconds for automatic doors. Settle plates averaged 2.47 CFU (range, 0.00-15), with higher average CFU from plates outside of LAF (3.60 CFU [range, 0.00-15.00]) compared to plates inside of LAF (0.93 CFU [range, 0.00-12.0]) (Fig 1). Increased door openings were statistically associated with higher CFU overall (P = .03) and for the subset of cultures outside of LAF (P = .0012) but not within LAF (P = .73; Table 1). Within LAF, number of staff in the OR was the only variable associated with higher CFU (P = .03; Table 1). None of the patients developed an SSI. Multivariable regression analysis was not performed because the variables that were significant on univariate analysis (surgery duration, number of door openings, and number of staff) demonstrated collinear coefficients ≥ 0.3. Increased number of door openings and surgery duration increased CFU counts in the OR, but the relationship between these variables was only observed outside LAF. Within LAF conditions, only the number of staff was associated with higher CFU. The relationship between increased staff and increased CFU within LAF may be due to a larger amount of bacterial shedding from healthcare workers. Researchers also observed temporary displacement of the back instrument table (containing settle plates) outside of LAF when greater numbers of people were involved in the case. This observation may have contributed to the increased CFU seen with high staff numbers and may account for the relationship seen between staff number and CFU in this study but not in other studies that did not use LAF.11Mathijssen N.M. Hannink G. Sturm P.D. Pilot P. Bloem R.M. Buma P. et al.The effect of door openings on numbers of colony forming units in the operating room during hip revision surgery.Surg Infect (Larchmt). 2016; 17: 535-540Crossref PubMed Scopus (14) Google Scholar In addition, the finding that CFU counts increased with door openings is in part accounted for by increased duration. We attempted to adjust for this by looking at CFU as a function of door openings per minute (Table 1). Door openings per minute showed a positive trend in CFU overall and outside LAF but was not statistically significant. These findings suggest that surgery duration contributes to, but does not fully explain, increased CFU counts. Limitations of the study include the possibility of the Hawthorne effect, as the procedures being studied were not blinded. The results of this study support the use of LAF and the reduction in number of staff in the OR as effective methods for reducing environmental contamination near the surgical site. In ORs without LAF, reducing door openings may be an effective way to reduce environmental contamination and prevent SSI. We would like to thank the staff in the microbiology laboratory for culture interpretation and the New England Baptist Hospital Department of Research for providing statistical support.