title: Xenon does not reduce opioid requirement for orthopedic surgery.
abstract: OBJECTIVE
  Is to test the hypothesis that 70% xenon has a relevant opioid sparing effect compared to a minimum alveolar concentration (MAC)-equivalent combination of N(2)O and desflurane.
  
  
  METHODS
  In this randomized, controlled study of 30 patients undergoing major orthopedic surgery, we determined the plasma alfentanil concentration required to suppress response to skin incision in 50% of patients (Cp(50)) anesthetized with xenon (70%) or a combination of N(2)O (70%) and desflurane (2%). A response was defined as movement, pressor response > 15 mmHg, heart rate > 90 beats x min(-1), autonomic reactions or a combination of these. At skin incision, alfentanil was administered at a randomly selected target plasma concentration thereafter the concentration was increased or decreased according to the patient's response. After skin incision, desflurane was adjusted to maintain the bispectral index below 60 and prevent responsiveness in both groups.
  
  
  RESULTS
  The Cp(50) (+/- standard error) of alfentanil was 83 +/- 48ng x mL(-1) with xenon and 49 +/- 26 ng x mL(-1) with N(2)O/desflurane (P =0.451). During surgery five xenon and 15 N(2)O/desflurane patients were given desflurane at 1.0 +/- 0.5 volume % and 2.5 +/- 0.7 volume %. The total age adjusted MAC was 0.97 +/- 0.07 and 0.94 +/- 0.07 respectively (P = 0.217). The intraoperative plasma alfentanil concentrations were 95 +/- 80 and 93 +/- 60 ng x mL(-1) respectively (mean +/- SD; P = 0.451). Patients given xenon were slightly more bradycardic, whereas blood pressure was similar.
  
  
  CONCLUSIONS
  Xenon compared to a MAC-equivalent combination of N(2)O and desflurane does not substantially reduce opioid requirement for orthopedic surgery. A small but clinically irrelevant difference cannot be excluded, however.
authors.affiliation: Department of Anesthesiology, University Hospital, CH-3010 Bern, Switzerland. martin.luginbuehl@dkf.unibe.ch
authors.forename: Martin
authors.initials: M
authors.lastname: Luginbühl
authors.forename: Steen
authors.initials: S
authors.lastname: Petersen-Felix
authors.forename: Alex M
authors.initials: AM
authors.lastname: Zbinden
authors.forename: Thomas W
authors.initials: TW
authors.lastname: Schnider
mesh_terms: D000328:Adult; D015760:Alfentanil / Q000008:administration & dosage / Q000493:pharmacokinetics / Q000627:therapeutic use; D000701:Analgesics, Opioid / Q000008:administration & dosage* / Q000493:pharmacokinetics / Q000627:therapeutic use*; D000769:Anesthesia, Inhalation; D018685:Anesthetics, Inhalation; D000077335:Desflurane; D004569:Electroencephalography / Q000187:drug effects; D005260:Female; D006439:Hemodynamics / Q000187:drug effects; D006801:Humans; D007530:Isoflurane / Q000031:analogs & derivatives*; D008297:Male; D016343:Monitoring, Intraoperative; D009609:Nitrous Oxide; D019637:Orthopedic Procedures; D010147:Pain Measurement; D010149:Postoperative Pain / Q000188:drug therapy*; D011292:Premedication; D014978:Xenon
chemical_list: D000701:Analgesics, Opioid; D018685:Anesthetics, Inhalation; D015760:Alfentanil; D014978:Xenon; D000077335:Desflurane; D007530:Isoflurane; D009609:Nitrous Oxide