title: Volume-outcome relationships in lower extremity arterial bypass surgery.
abstract: OBJECTIVE
  We sought to investigate whether a volume-outcome relationship exists for lower extremity arterial bypass (LEAB) surgery.
  
  
  METHODS
  All LEAB procedures performed in England between 2002 and 2006 were identified from Hospital Episode Statistics data. A Charlson-type risk profile, including operating hospital annual case volume, was identified per patient. Outcome measures of revision bypass, amputation, death and a composite measure were established during the index admission and at 1 year.Quintile analysis and multilevel multivariate modeling were used to identify the existence of a volume-outcome relationship and allow adjustment of results for significant determinants of outcome.
  
  
  RESULTS
  A total of 27,660 femoropopliteal bypass and 4161 femorodistal bypass procedures were identified.As volume increased, in-hospital mortality after popliteal bypass decreased from 6.5% to 4.9% (P = 0.0045), with a corresponding odds ratio of 0.980 [95% confidence interval (CI), 0.929-0.992; P = 0.014] for every increase of 50 patients per year. Major amputation decreased from 4.1% to 3.2% (P = 0.006) in high-volume hospitals, with a reduction in risk of 0.955 (95% CI, 0.928-0.983; P = 0.002) at 1 year.For distal bypass, in-hospital mortality decreased from 9.8% to 5.5% (P = 0.004) and 1-year major amputation decreased from 25.4% to 18.2% (P < 0.001), with a corresponding odds ratio of 0.658 (95% CI, 0.517-0.838; P < 0.0001) as the volume increased.An increase in the chance of revision surgery (10.6% vs 8.2%, P < 0.001) was seen with higher volume, with an increased odds ratio of 1.031 (95% CI, 1.005-1.057; P = 0.018).
  
  
  CONCLUSIONS
  A positive volume-outcome relationship exists for LEAB procedures even after employing multilevel risk adjustment models. There are benefits in terms of mortality and limb salvage both in the short-term and at 1 year postsurgery.
authors: Department of Outcomes Research, St George's Vascular Institute, St George's Healthcare NHS Trust, London, UK. paul.moxey@nhs.net
authors: Paul W
authors: PW
authors: Moxey
authors: David
authors: D
authors: Hofman
authors: Rob J
authors: RJ
authors: Hinchliffe
authors: Jan
authors: J
authors: Poloniecki
authors: Ian M
authors: IM
authors: Loftus
authors: Matt M
authors: MM
authors: Thompson
authors: Peter J
authors: PJ
authors: Holt
mesh_terms: D000368:Aged; D005260:Female; D006801:Humans; D035002:Lower Extremity / Q000098:blood supply* / Q000601:surgery*; D008297:Male; D015999:Multivariate Analysis; D012189:Retrospective Studies; D016896:Treatment Outcome; D014656:Vascular Surgical Procedures / Q000706:statistics & numerical data*