title: Prospective observational study of the non-invasive assessment of immediate postoperative pain using the analgesia/nociception index (ANI).
abstract: BACKGROUND
  The analgesia/nociception index (ANI), a 0-100 non-invasive index calculated from heart rate variability, reflects the analgesia/nociception balance during general anaesthesia. The aim of this study was to evaluate the ANI in the assessment of immediate postoperative pain in adult patients undergoing general anaesthesia.
  
  
  METHODS
  Two-hundred patients undergoing scheduled surgery or endoscopy with general anaesthesia were included in this prospective observational study. Pain intensity was assessed using a 0-10 numerical rating scale (NRS) after arousal from general anaesthesia. Receiver-operating characteristic (ROC) curves were built to assess the performance of ANI to detect patients with NRS>3 and NRS ≥ 7 on arrival in the postoperative care unit.
  
  
  RESULTS
  A negative linear relationship was observed between ANI and NRS (ANI=-5.2 × NRS+77.9, r(2)=0.41, P<0.05). At the threshold of 57, the sensitivity and specificity of ANI to detect patients with NRS>3 were 78 and 80%, respectively, with a negative predictive value of 88%, corresponding to an area under the ROC curve (AUC) of 0.86. At the threshold of 48, the sensitivity and specificity of ANI to detect NRS ≥ 7 were 92 and 82%, respectively, with a negative predictive value of 99%, corresponding to a ROC curve AUC of 0.91.
  
  
  CONCLUSIONS
  A measurement of ANI during the immediate postoperative period is significantly correlated with pain intensity. The measurement of ANI appears to be a simple and non-invasive method to assess immediate postoperative analgesia.
authors.affiliation: Department of Anaesthesiology and Intensive Care, Édouard Herriot Hospital, Hospices Civils de Lyon, Lyon, France. emmanuel.boselli@chu-lyon.fr
authors.forename: E
authors.initials: E
authors.lastname: Boselli
authors.forename: M
authors.initials: M
authors.lastname: Daniela-Ionescu
authors.forename: G
authors.initials: G
authors.lastname: Bégou
authors.forename: L
authors.initials: L
authors.lastname: Bouvet
authors.forename: R
authors.initials: R
authors.lastname: Dabouz
authors.forename: C
authors.initials: C
authors.lastname: Magnin
authors.forename: B
authors.initials: B
authors.lastname: Allaouchiche
mesh_terms: D000328:Adult; D000698:Analgesia; D000768:Anesthesia, General; D019540:Area Under Curve; D005260:Female; D006339:Heart Rate / Q000187:drug effects; D006801:Humans; D008297:Male; D059225:Nociception / Q000187:drug effects*; D010147:Pain Measurement / Q000379:methods*; D010149:Postoperative Pain / Q000175:diagnosis*; D011446:Prospective Studies; D012372:ROC Curve; D012680:Sensitivity and Specificity
keywords: analgesia/nociception index; assessment; pain; postoperative