title: Time-dependent contamination of opened sterile operating-room trays.
abstract: BACKGROUND
  There are no clear guidelines for how long a sterile operating-room tray can be exposed to the open environment before the contamination risk becomes unacceptable. The purpose of this study was to determine the time until first contamination and the rate of time-dependent contamination of sterile trays that had been opened in a controlled operating-room environment. We also examined the effect of operating-room traffic on the contamination rate.
  
  
  METHODS
  Forty-five sterile trays were opened in a positive-air-flow operating room. The trays were randomly assigned to three groups. All trays were opened with use of sterile technique and were exposed for four hours. Culture specimens were obtained immediately after opening and every thirty minutes thereafter during the study period. Group 1 consisted of fifteen trays that were opened and left uncovered in a locked operating room (i.e., one with no traffic). Group 2 was identical to Group 1 with the addition of single-person traffic flowing in and out of the operating room from a nonsterile corridor every ten minutes. Group 3 included fifteen trays that were opened, immediately covered with a sterile surgical towel, and then left uncovered in a locked operating room (i.e., one with no traffic).
  
  
  RESULTS
  Three of the thirty uncovered trays (one left in the operating room with traffic and two left in the room with no traffic) were found to be contaminated immediately after opening. After those three trays were eliminated, the contamination rates recorded for the twenty-seven uncovered trays were 4% (one tray) at thirty minutes, 15% (four) at one hour, 22% (six) at two hours, 26% (seven) at three hours, and 30% (eight) at four hours. There was no difference in survival time (p = 0.47) or contamination rate (p = 0.69) between the uncovered trays in the room with traffic and those in the room without traffic. The covered trays were not contaminated during the testing period. The survival time for those trays was significantly longer (p = 0.03) and the contamination rate was significantly lower (p = 0.02) than those for the uncovered trays.
  
  
  CONCLUSIONS
  Culture positivity correlated directly with the duration of open exposure of the uncovered operating-room trays. Light traffic in the operating room appeared to have no impact on the contamination risk. Coverage of surgical trays with a sterile towel significantly reduced the contamination risk.
authors.affiliation: Orthopaedic Surgery Residency Program, Miami Valley Hospital, 128 East Apple Street, Suite 2830, Dayton, OH 45409, USA. orthodjd@yahoo.com
authors.forename: David J
authors.initials: DJ
authors.lastname: Dalstrom
authors.forename: Indresh
authors.initials: I
authors.lastname: Venkatarayappa
authors.forename: Alison L
authors.initials: AL
authors.lastname: Manternach
authors.forename: Marilyn S
authors.initials: MS
authors.lastname: Palcic
authors.forename: Beth A
authors.initials: BA
authors.lastname: Heyse
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Prayson
mesh_terms: D000391:Air Microbiology; D015169:Colony Count, Microbial; D003428:Cross Infection / Q000517:prevention & control; D004866:Equipment Contamination / Q000517:prevention & control*; D006801:Humans; D053208:Kaplan-Meier Estimate; D009873:Operating Rooms; D019637:Orthopedic Procedures; D013242:Sterilization; D013523:Surgical Equipment / Q000382:microbiology*; D013530:Surgical Wound Infection / Q000517:prevention & control*; D013997:Time Factors