title: The acute surgical unit model verses the traditional "on call" model: a systematic review and meta-analysis.
abstract: BACKGROUND
  The acute surgical unit (ASU) is a novel model for the provision of emergency general surgery care. The ASU model was initially developed in New South Wales hospitals during 2005 and 2006. Several studies have analysed the effects on patient outcomes and timeliness of care for nontrauma patients presenting with acute general surgical conditions. The purpose of this study was to perform a meta-analysis to determine the efficacy of the ASU model compared with the traditional on-call model for specific conditions.
  
  
  METHODS
  A systematic search was conducted using MEDLINE, PubMed, EMBASE, Current Contents Connect, Cochrane library, Google Scholar, Science Direct, and Web of Science. Original data were extracted from each study and used to calculate a pooled odd ratio (OR) and 95 % confidence interval (CI).
  
  
  RESULTS
  The search identified 18 studies; appendectomy (n = 9), acute cholecystitis (n = 7), and small-bowel obstruction (SBO) (n = 2). In the appendectomy cohort, the proportion of appendicular perforation were similar in pre-ASU and ASU period (OR 1.02, 95 % CI 0.77-1.37, p = 0.13). The incidence of complications in the appendectomy cohort was significantly lower in the ASU group; 14.5 % pre-ASU and 10.9 % post-ASU (OR 1.649, 95 % CI 0.732-3.714, p = 0.009). The negative appendectomy rate was similar for the pre- and post-ASU groups (OR 1.07, 95 % CI 0.88-1.31, p = 0.83). Likewise the conversion rate to open surgery and total hospital stay were similar between the two groups. The proportion of night time operations reduced significantly in the ASU period (OR 1.9, 95 % CI 1.32-2.74, p = 0.001). In the acute cholecystitis cohort, the conversion rate to open surgery was significantly higher in the pre-ASU group (15.1 %) compared with the post-ASU group (7.5 %) (OR 1.879, 95 % CI 1.072-3.293, p = 0.04) The incidence of complications was higher in the pre-ASU (14 %) compared with the post-ASU (6.8 %) group (OR 2.231, 95 % CI 1.372-3.236, p = 0.03). The mean hospital stay was significantly lower in the ASU period (5.3 vs. 3.7 days, p = 0.0063). There was insufficient data available to analyse outcomes for SBO.
  
  
  CONCLUSIONS
  The ASU model provides a safe surgical environment for patients and is associated with a reduced complication rate for appendectomy and laparoscopic cholecystectomy for acute cholecystitis. There is a reduced conversion rate and a shorter length of stay for patients with acute cholecystitis. Overall, the ASU model has translated to better outcomes for patients presenting with acute general surgical conditions.
authors.affiliation: The Whiteley-Martin Research Centre, The Discipline of Surgery, Sydney Medical School, The University of Sydney, Nepean Hospital, Level 5, South Block, Penrith, NSW, 2751, Australia.
authors.forename: Vinayak
authors.initials: V
authors.lastname: Nagaraja
authors.forename: Guy D
authors.initials: GD
authors.lastname: Eslick
authors.forename: Michael R
authors.initials: MR
authors.lastname: Cox
mesh_terms: D001062:Appendectomy / Q000379:methods / Q000706:statistics & numerical data; D001064:Appendicitis / Q000175:diagnosis / Q000601:surgery*; D002763:Cholecystectomy / Q000379:methods / Q000706:statistics & numerical data; D041881:Cholecystitis, Acute / Q000175:diagnosis / Q000601:surgery*; D004636:Emergency Service, Hospital / Q000458:organization & administration*; D004638:Emergency Treatment; D005260:Female; D006801:Humans; D007902:Length of Stay; D008297:Male; D017146:Models, Organizational; D009517:New South Wales; D011183:Postoperative Complications / Q000453:epidemiology / Q000503:physiopathology; D011787:Quality of Health Care; D013503:Surgery Department, Hospital / Q000458:organization & administration*