title: An investigation on influential factors of patient-controlled epidural analgesic requirement over time for upper abdominal surgeries.
abstract: BACKGROUND
  Patient-controlled epidural analgesia (PCEA) is commonly used to relieve postoperative pain for upper abdominal surgeries. However, there is still a lack of studies exploring factors associated with PCEA consumption over time after upper abdominal surgery; our study intended to provide further elucidation about this issue.
  
  
  METHODS
  This study retrospectively evaluated postoperative PCEA consumption over time after upper abdominal surgery. Cumulative PCEA consumption in the first four 12-hour intervals was directly retrieved from the data recorded by infusion pumps. Potentially influential factors of PCEA requirements, including demographic variables and infusion pump settings, were also collected. A linear mixed model was applied to investigate the relationships between these factors and PCEA consumption over time. A backward elimination strategy was used to select independent factors significantly associated with PCEA consumption.
  
  
  RESULTS
  A total of 1001 patients were included in the analysis. On average, PCEA consumption after upper abdominal surgery peaked during the 2(nd) 12-hour interval and then decreased gradually over time. After the model selection processes were completed, four independent factors were identified to have significant effects on PCEA consumption. Surgery for malignant disease and background infusion rate were positively associated with PCEA consumption and did not interact with time. Additionally, female patients tended to consume less and less PCEA over time relative to males. Age had a negative effect on PCEA consumption, which peaked during the 2(nd) 12-hour interval and then decreased gradually over time. The final selected model exhibited acceptable predictive power relative to the observed data.
  
  
  CONCLUSIONS
  Our analyses provided valuable information about the factors associated with PCEA consumption over time after upper abdominal surgery. However, the mechanism of how these factors interact over the course of time awaits further investigation.
authors.affiliation: Department of Anesthesiology, Taipei Veterans General Hospital and National Yang-Ming University School of Medicine, Taipei, Taiwan, ROC.
authors.forename: Ken-Hua
authors.initials: KH
authors.lastname: Hu
authors.forename: Mei-Yung
authors.initials: MY
authors.lastname: Tsou
authors.forename: Kwok-Hon
authors.initials: KH
authors.lastname: Chan
authors.forename: Kuang-Yi
authors.initials: KY
authors.lastname: Chang
mesh_terms: D000005:Abdomen / Q000601:surgery*; D000328:Adult; D000368:Aged; D015360:Analgesia, Epidural; D016058:Analgesia, Patient-Controlled; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010149:Postoperative Pain / Q000628:therapy*; D012189:Retrospective Studies
keywords: general anesthesia; linear mixed model; patient-controlled epidural analgesia; upper abdominal surgery