title: Increased anaesthesia duration increases venous thromboembolism risk in plastic surgery: A 6-year analysis of over 19,000 cases using the NSQIP dataset.
abstract: BACKGROUND
  Venous thromboembolism (VTE) is a significant cause of morbidity and mortality, particularly in the postoperative setting. Various risk stratification schema exist in the plastic surgery literature, but do not take into account variations in procedure length. The putative risk of VTE conferred by increased length of time under anaesthesia has never been rigorously explored.
  
  
  OBJECTIVE
  The goal of this study is to assess this relationship and to benchmark VTE rates in plastic surgery.
  
  
  METHODS
  A large, multi-institutional quality-improvement database was queried for plastic and reconstructive surgery procedures performed under general anaesthesia between 2005-2011. In total, 19,276 cases were abstracted from the database. Z-scores were calculated based on procedure-specific mean surgical durations, to assess each case's length in comparison to the mean for that procedure. A total of 70 patients (0.36%) experienced a post-operative VTE. Patients with and without post-operative VTE were compared with respect to a variety of demographics, comorbidities, and intraoperative characteristics. Potential confounders for VTE were included in a regression model, along with the Z-scores.
  
  
  RESULTS
  VTE occurred in both cosmetic and reconstructive procedures. Longer surgery time, relative to procedural means, was associated with increased VTE rates. Further, regression analysis showed increase in Z-score to be an independent risk factor for post-operative VTE (Odds Ratio of 1.772 per unit, p-value < 0.001). Subgroup analyses corroborated these findings.
  
  
  CONCLUSIONS
  This study validates the long-held view that increased surgical duration confers risk of VTE, as well as benchmarks VTE rates in plastic surgery procedures. While this in itself does not suggest an intervention, surgical time under general anaesthesia would be a useful addition to existing risk models in plastic surgery.
authors.affiliation: Division of Plastic and Reconstructive Surgery, Northwestern University, Feinberg School of Medicine , Chicago, IL , USA.
authors.forename: Alexei S
authors.initials: AS
authors.lastname: Mlodinow
authors.forename: Nima
authors.initials: N
authors.lastname: Khavanin
authors.forename: Jon P
authors.initials: JP
authors.lastname: Ver Halen
authors.forename: Aksharananda
authors.initials: A
authors.lastname: Rambachan
authors.forename: Karol A
authors.initials: KA
authors.lastname: Gutowski
authors.forename: John Y S
authors.initials: JY
authors.lastname: Kim
mesh_terms: D000328:Adult; D000768:Anesthesia, General / Q000009:adverse effects*; D003357:Cosmetic Techniques; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D061646:Operative Time; D011183:Postoperative Complications / Q000453:epidemiology*; D019651:Plastic Surgery Procedures; D012042:Registries; D012044:Regression Analysis; D012307:Risk Factors; D014481:United States / Q000453:epidemiology; D054556:Venous Thromboembolism / Q000453:epidemiology*
keywords: Complication; breast; flaps; plastic surgery