title: Analysis of risk factors associated with microvascular free flap failure using a multi-institutional database.
abstract: BACKGROUND
  There are numerous factors that may contribute to microvascular free flap failure. Although technical issues are dominant factors, patient and clinical characteristics are also contributory. The aim of this study was to investigate non-technical variables associated with microsurgical free flap failure using a multi-institutional dataset.
  
  
  METHODS
  Utilizing the American College of Surgeons' National Surgical Quality Improvement Program (NSQIP) database, we identified all patients who underwent microvascular free tissue transfer from 2005 through 2009. Univariate analysis was performed to determine the association of flap failure with the following factors: age, gender, ethnicity, body mass index, intraoperative transfusion, diabetes, smoking, alcohol, American Society of Anesthesiologists classification, year of operation, operative time, number of flaps, and type of reconstruction. Factors with a significance of P < 0.2 in the univariate analysis were included in the multivariate logistic regression model to identify independent risk factors.
  
  
  RESULTS
  A total of 639 patients underwent microsurgical free flap reconstruction with 778 flaps over the 4-year study period; 139 patients had two free flaps during the same operation. The overall incidence of flap failure was 4.4% (34/778) (95% confidence interval [CI]: 3.0%, 6.2%). Operative time was identified as an independent risk factor for free flap failure. After adjusting for other factors, those whose operative time was equal to or greater than the 75th percentile (625.5 min) were twice as likely to experience flap failure (AOR 2.09; 95% CI: 1.01-4.31; P = 0.045). None of the other risk factors studied were significant contributors.
  
  
  CONCLUSIONS
  In this series, the overall flap loss rate of was 4.4%. Operative time was a significant independent risk factor for flap failure.
authors.affiliation: Division of Plastic and Reconstructive Surgery, Keck School of Medicine of USC, Los Angeles, CA.
authors.forename: Alex K
authors.initials: AK
authors.lastname: Wong
authors.forename: T
authors.initials: T
authors.lastname: Joanna Nguyen
authors.forename: Mirna
authors.initials: M
authors.lastname: Peric
authors.forename: Ahva
authors.initials: A
authors.lastname: Shahabi
authors.forename: Evan N
authors.initials: EN
authors.lastname: Vidar
authors.forename: Brian H
authors.initials: BH
authors.lastname: Hwang
authors.forename: Solmaz
authors.initials: S
authors.lastname: Niknam Leilabadi
authors.forename: Linda S
authors.initials: LS
authors.lastname: Chan
authors.forename: Mark M
authors.initials: MM
authors.lastname: Urata
mesh_terms: D000328:Adult; D000368:Aged; D002140:California; D016208:Databases, Factual; D017707:Erythrocyte Transfusion; D005260:Female; D058752:Free Tissue Flaps / Q000601:surgery*; D006085:Graft Survival; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D016017:Odds Ratio; D061646:Operative Time; D011183:Postoperative Complications / Q000453:epidemiology / Q000209:etiology*; D019651:Plastic Surgery Procedures; D012044:Regression Analysis; D012307:Risk Factors