title: Changes in a surgical stress index in response to standardized pain stimuli during propofol-remifentanil infusion.
abstract: BACKGROUND
  The surgical stress index (SSI) is based on a sum of the normalized pulse beat interval (PBI) and the pulse wave amplitude (PPGA) time series of the photoplethysmography. As a measure of the nociception-anti-nociception balance in response to a standardized pain stimulus, SSI was compared with EEG changes in state and response entropy (SE and RE), PPGA, and heart rate (HR) during various targeted pseudo-steady-state concentrations of propofol and remifentanil.
  
  
  METHODS
  Forty ASA I patients were allocated to one of the four groups to receive a remifentanil step-up/-down effect-compartment target-controlled infusion (Ce(remi)) of 0, 2, 6, 2, 0 ng ml(-1), or 6, 2, 0, 2, 6 ng ml(-1), and an effect-compartment target-controlled propofol infusion (Ce(prop)) to keep the SE between 30 and 50 or 15 and 30, respectively. At each steady-state Ce(remi), maximum change in SSI, SE, RE, PPGA, and HR after a noxious stimulus was compared with the baseline value. A correlation and prediction probability (P(K)) with Ce(prop) and Ce(remi) was measured.
  
  
  RESULTS
  Static and dynamic values of SSI correlated to Ce(remi) better than SE, RE, HR, and PPGA. SSI was independent of Ce(prop), in contrast to SE and RE. The P(K) for Ce(remi) both before and during a noxious stimulus was better with SSI.
  
  
  CONCLUSIONS
  SSI appeared to be a better measure of nociception-anti-nociception balance than SE, RE, HR, or PPGA.
authors.affiliation: Department of Anaesthesia, Ghent University Hospital, De Pintelaan 185, B-9000 Ghent, Belgium. michel.struys@ugent.be
authors.forename: M M R F
authors.initials: MM
authors.lastname: Struys
authors.forename: C
authors.initials: C
authors.lastname: Vanpeteghem
authors.forename: M
authors.initials: M
authors.lastname: Huiku
authors.forename: K
authors.initials: K
authors.lastname: Uutela
authors.forename: N B K
authors.initials: NB
authors.lastname: Blyaert
authors.forename: E P
authors.initials: EP
authors.lastname: Mortier
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000701:Analgesics, Opioid / Q000008:administration & dosage / Q000494:pharmacology*; D004334:Drug Administration Schedule; D004569:Electroencephalography / Q000187:drug effects; D019277:Entropy; D005260:Female; D006339:Heart Rate / Q000187:drug effects; D006801:Humans; D008297:Male; D008875:Middle Aged; D016343:Monitoring, Intraoperative / Q000379:methods*; D010147:Pain Measurement / Q000379:methods; D017156:Photoplethysmography; D010880:Piperidines / Q000008:administration & dosage / Q000494:pharmacology*; D015742:Propofol / Q000008:administration & dosage / Q000494:pharmacology*; D000077208:Remifentanil; D012815:Signal Processing, Computer-Assisted; D013312:Stress, Physiological / Q000209:etiology / Q000503:physiopathology* / Q000517:prevention & control
chemical_list: D000701:Analgesics, Opioid; D010880:Piperidines; D000077208:Remifentanil; D015742:Propofol