title: Operative Start Time Does Not Affect Post-Operative Infection Risk.
abstract: BACKGROUND
  Surgical care is delivered 24 h a day at most institutions. Alarmingly, some authors have found that certain operative start times are associated with greater morbidity and mortality rates. This effect has been noted in both the public and private sector. Although some of these differences may be related to process, they may also be caused by the human circadian rhythm and corresponding changes in host defenses. We hypothesized that the time of day of an operation would impact the frequency of certain post-operative outcomes significantly.
  
  
  METHODS
  Cases at a single tertiary-care center reported to the American College of Surgeons National Surgical Quality Improvement Program over a 10-year period were identified. Operative start times were divided into six-hour blocks, with 6 am to noon serving as the reference. Standard univariable techniques were applied. Multivariable logistic regression with mixed effects modeling then was used to determine the relation between operative start times and infectious outcomes, controlling for surgeon clustering. Statistical significance was set at p < 0.01.
  
  
  RESULTS
  A total of 21,985 cases were identified, of which 2,764 (12.6%) were emergency procedures. Overall, 9.7% (n = 2,142) of patients experienced some post-operative infectious complication. Seventy percent of these infections (n = 1,506) were surgical site infections. On univariable analysis considering all cases, nighttime and evening operations had higher rates of post-operative infections than those in performed during the day (9.1% from 6 am to noon; 9.7% from noon to 6 pm; 14.8% from 6 pm to midnight; and 14.4% from midnight to 6 am; p < 0.001). On multivariable analysis, operative start time was not associated with the risk of post-operative infection, even when emergency cases were considered independently.
  
  
  CONCLUSIONS
  Our data suggest that operative start times have no correlation with post-operative infectious complications. Further work is required to identify the source of the time-dependent outcome variability observed in previous studies.
authors.affiliation: 1 Department of Surgery, The University of Virginia Health System , Charlottesville, Virginia.
authors.forename: Christopher A
authors.initials: CA
authors.lastname: Guidry
authors.affiliation: 1 Department of Surgery, The University of Virginia Health System , Charlottesville, Virginia.
authors.forename: Stephen W
authors.initials: SW
authors.lastname: Davies
authors.affiliation: 1 Department of Surgery, The University of Virginia Health System , Charlottesville, Virginia.
authors.forename: Rhett N
authors.initials: RN
authors.lastname: Willis
authors.affiliation: 1 Department of Surgery, The University of Virginia Health System , Charlottesville, Virginia.
authors.forename: Zachary C
authors.initials: ZC
authors.lastname: Dietch
authors.affiliation: 1 Department of Surgery, The University of Virginia Health System , Charlottesville, Virginia.
authors.forename: Puja M
authors.initials: PM
authors.lastname: Shah
authors.affiliation: 1 Department of Surgery, The University of Virginia Health System , Charlottesville, Virginia.|2 Division of Acute Care Surgery and Outcomes Research, The University of Virginia Health System , Charlottesville, Virginia.
authors.forename: Robert G
authors.initials: RG
authors.lastname: Sawyer
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D061646:Operative Time; D059035:Perioperative Period / Q000706:statistics & numerical data*; D057234:Preoperative Period; D012189:Retrospective Studies; D013530:Surgical Wound Infection / Q000453:epidemiology* / Q000401:mortality; D013997:Time Factors