title: Effect of patient load on trauma outcomes in a Level I trauma center.
abstract: OBJECTIVE
  Increased medical staff workload has been associated with worse outcomes in several studies. Inappropriate staffing has also been implicated in the increased risk of mortality for medical patients admitted on weekends. A theoretical threshold patient load may exist, beyond which the resources are strained and patient outcomes suffer. The goal of the study was to see whether trauma patients admitted during 'high' patient-load periods, at night, or on weekends had worse outcomes.
  
  
  METHODS
  Trauma patients admitted to a high-volume Level I trauma center from 1994 to 2002 were analyzed. Patient load was defined as a combination of the number of patients admitted and the severity of their illness. On the basis of a multivariate regression model, a probability of fatal outcome was calculated for each patient as a marker for the severity of illness. For each patient, two new variables were calculated, the number of admissions (#ad) and the average probability of fatal outcome (PFO) for the 24-hour period in which the patient was admitted (excluding the patient him- or herself). The above variables, night/d, and weekend/d were placed in a multivariate regression model.
  
  
  RESULTS
  There were 30,686 patients. Age, mechanism of injury, Injury Severity Score, maximum head Abbreviated Injury Scale score, admission Glasgow Coma Scale score, systolic blood pressure, and intubation status were the independent predictors of mortality. This model had an outstanding predictive power, with an area under the receiver operating characteristic curve of 0.96. The mean #ad was 11 +/- 4 and PFO was 0.08 +/- 0.07. Values above the 90th percentile were considered 'high' for #ad > 17 or PFO > 0.18. There was no difference in mortality for patients admitted during high #ad (odds ratio [OR], 0.95; p = 0.7) or high PFO (OR, 0.99; p = 0.9) versus low. There was no difference in mortality if a patient was admitted on weekends versus weekdays (OR, 0.9; p = 0.2) or at night versus day (OR, 0.9; p = 0.2). There was no difference in hospital length of stay for high #ad, high PFO, nights, or weekends.
  
  
  CONCLUSIONS
  At this Level I trauma center that is part of an established statewide trauma system, patient outcomes were not compromised during high-patient-load periods, at night, or on weekends.
authors.affiliation: Department of Surgery, University of Michigan, Ann Arbor, USA. sarbabi@med.umich.edu
authors.forename: Saman
authors.initials: S
authors.lastname: Arbabi
authors.forename: Gregory J
authors.initials: GJ
authors.lastname: Jurkovich
authors.forename: Wendy L
authors.initials: WL
authors.lastname: Wahl
authors.forename: Hyungjin Myra
authors.initials: HM
authors.lastname: Kim
authors.forename: Ronald V
authors.initials: RV
authors.lastname: Maier
mesh_terms: D000328:Adult; D001794:Blood Pressure; D005260:Female; D015600:Glasgow Coma Scale; D006801:Humans; D015601:Injury Severity Score; D007902:Length of Stay; D008297:Male; D011237:Predictive Value of Tests; D012372:ROC Curve; D013997:Time Factors; D014193:Trauma Centers / Q000706:statistics & numerical data*; D016526:Workload / Q000706:statistics & numerical data*; D014947:Wounds and Injuries / Q000145:classification* / Q000401:mortality