title: Prediction of post-operative pain following arthroscopic subacromial decompression surgery: an observational study.
abstract: BACKGROUND
  Arthroscopic shoulder surgery is increasingly performed as a day case procedure. Optimal post-operative pain relief remains a challenge due to considerable variations in the level of pain experienced between individuals. Our aim was to examine whether the preoperative electrical pain threshold was a strong predictor of elevated postoperative pain levels following arthroscopic subacromial decompression (ASD) surgery.
  
  
  METHODS
  Forty consenting patients with American Society of Anesthesiologists (ASA) grade 1-2 presenting for elective ASD surgery were recruited. Patients' electrical pain thresholds were measured preoperatively using a PainMatcher® (Cefar Medical AB, Lund, Sweden) device. Following surgery under general anaesthesia, the maximum pain experienced at rest and movement was recorded using a visual analogue scale until the end of postoperative day four.
  
  
  RESULTS
  In univariate analyses (t-test), the postoperative pain experienced (Area Under Curve) was significantly greater in patients with a low pain threshold as compared with a high pain threshold at both rest (mean 12.5, S.E. 1.7 v mean 6.5, S.E.1.2. P=0.008) and on movement (mean 18.7, S.E. 1.5 v mean 14.1, S.E.1.4. P=0.031). In multivariate analyses, adjusting for additional extra analgesia, the pain experienced postoperatively was significantly greater in the low pain threshold group both at rest (mean difference 4.9, 95% CI 1.5 to 8.4, P=0.007) and on movement (mean difference 4.1, 95%CI 0.03 to 8.2, P=0.049).
  
  
  CONCLUSIONS
  Preoperative pain threshold can predict postoperative pain level following ASD of the shoulder.
  
  
  BACKGROUND
  Clinicaltrials.gov identifier: NCT01351363 LEVEL OF EVIDENCE: II.
authors.affiliation: Anesthesiology Department, NHS Fife, Victoria Hospital, Kirkcaldy, Fife, KY2 5AH, UK.
authors.forename: Anthony
authors.initials: A
authors.lastname: Davis
authors.affiliation: Research and Development, NHS Fife, Lynebank Hospital, Dunfermline, Fife, KY11 4UW, UK.
authors.forename: David J
authors.initials: DJ
authors.lastname: Chinn
authors.affiliation: Orthopaedics, NHS Fife, Victoria Hospital, Kirkcaldy, Fife, KY2 5AH, UK.
authors.forename: Sunil
authors.initials: S
authors.lastname: Sharma