title: Identifying patients at high risk for venous thromboembolism requiring treatment after outpatient surgery.
abstract: OBJECTIVE
  To identify independent predictors of 30-day venous thromboembolism (VTE) events requiring treatment after outpatient surgery.
  
  
  BACKGROUND
  An increasing proportion of surgical procedures are performed in the outpatient setting. The incidence of VTE requiring treatment after outpatient surgery is unknown.
  
  
  METHODS
  Prospective observational cohort study using the American College of Surgeons National Surgical Quality Improvement Program (ACS-NSQIP) database from 2005 to 2009. Adult patients who had outpatient surgery or surgery with subsequent 23-hour observation were included. The main outcome measure was 30-day VTE requiring treatment. Patients were randomly assigned to derivation (N = 173,501) or validation (N = 85,730) cohorts. Logistic regression examined independent risk factors for 30-day VTE. A weighted risk index was created and applied to the validation cohort. Stratified analyses examined 30-day VTE by risk level.
  
  
  RESULTS
  Thirty-day incidence of VTE for the overall cohort was 0.15%. Independent risk factors included current pregnancy (adjusted odds ratio [OR] = 7.80, P = 0.044), active cancer (OR = 3.66, P = 0.005), age 41 to 59 years (OR = 1.72, P = 0.008), age 60 years or more (OR = 2.48, P < 0.001), body mass index 40 kg/m or higher (OR = 1.81, P = 0.015), operative time 120 minutes or more (OR = 1.69, P = 0.027), arthroscopic surgery (OR = 5.16, P < 0.001), saphenofemoral junction surgery (OR = 13.20, P < 0.001), and venous surgery not involving the great saphenous vein (OR = 15.61, P < 0.001). The weighted risk index identified a 20-fold variation in 30-day VTE between low (0.06%) and highest risk (1.18%) patients.
  
  
  CONCLUSIONS
  Thirty-day VTE risk after outpatient surgery can be quantified using a weighted risk index. The risk index identifies a high-risk subgroup of patients with 30-day VTE rates of 1.18%.
authors.affiliation: Section of Plastic Surgery, University of Michigan, Ann Arbor, MI 48105, USA. cpannucc@umich.edu
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Pannucci
authors.forename: Amy
authors.initials: A
authors.lastname: Shanks
authors.forename: Marc J
authors.initials: MJ
authors.lastname: Moote
authors.forename: Vinita
authors.initials: V
authors.lastname: Bahl
authors.forename: Paul S
authors.initials: PS
authors.lastname: Cederna
authors.forename: Norah N
authors.initials: NN
authors.lastname: Naughton
authors.forename: Thomas W
authors.initials: TW
authors.lastname: Wakefield
authors.forename: Peter K
authors.initials: PK
authors.lastname: Henke
authors.forename: Darrell A
authors.initials: DA
authors.lastname: Campbell
authors.forename: Sachin
authors.initials: S
authors.lastname: Kheterpal
mesh_terms: D000328:Adult; D000556:Ambulatory Surgical Procedures / Q000009:adverse effects*; D016208:Databases, Factual; D005260:Female; D005544:Forecasting; D006801:Humans; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D011247:Pregnancy; D011446:Prospective Studies; D011897:Random Allocation; D018570:Risk Assessment; D012307:Risk Factors; D016896:Treatment Outcome; D054556:Venous Thromboembolism / Q000209:etiology* / Q000628:therapy