title: Preoperative "fentanyl challenge" as a tool to estimate postoperative opioid dosing in chronic opioid-consuming patients.
abstract: When opioids are used for postoperative pain control, it is useful to define the dose-response relationship for analgesia and respiratory depression. We studied 20 chronically opioid-consuming patients having elective multilevel spine fusion. Preoperatively, each patient received a fentanyl infusion of 2 microg x kg(-1) x min(-1) until the respiratory rate was <5 breaths/min. Pharmacokinetic simulations were used to estimate the effect site concentration at the time of respiratory depression and to predict the patient-controlled analgesia settings that would provide an effect-site fentanyl concentration that was 30% of the concentration associated with respiratory depression. Postoperatively, patient-controlled analgesia settings were adjusted to achieve 2-3 demand doses per hour. At steady-state patient-controlled analgesia settings, arterial blood gases and plasma fentanyl levels were measured. Sixteen patients required no adjustment or one patient-controlled analgesia adjustment. The median arterial Pco(2) level was 41 mm Hg and the interquartile range was 39-46 mm Hg. Plasma fentanyl levels demonstrated a significant correlation to the estimated effect-site concentration associated with respiratory depression determined during the preoperative fentanyl challenge. A preoperative fentanyl challenge used with pharmacokinetic simulations may be a useful tool to individualize the administration of analgesics to chronically opioid-consuming patients.
  
  
  CONCLUSIONS
  In chronically opioid-consuming patients, doses causing respiratory depression and analgesia may differ from those in opioid-naive individuals. A preoperative infusion of fentanyl, used in conjunction with pharmacokinetic simulation, may be a valuable tool for identifying clinical end-points, such as respiratory depression and analgesia, and individualizing postoperative treatment of pain in patients who chronically consume opioids.
authors.affiliation: Department of Anesthesiology at the University of Utah Medical Center, Salt Lake City, Utah.
authors.forename: Jennifer J
authors.initials: JJ
authors.lastname: Davis
authors.forename: Jeffrey D
authors.initials: JD
authors.lastname: Swenson
authors.forename: Robert H
authors.initials: RH
authors.lastname: Hall
authors.forename: Jeffrey D
authors.initials: JD
authors.lastname: Dillon
authors.forename: Ken B
authors.initials: KB
authors.lastname: Johnson
authors.forename: Talmage D
authors.initials: TD
authors.lastname: Egan
authors.forename: Nathan L
authors.initials: NL
authors.lastname: Pace
authors.forename: Su-Yi
authors.initials: SY
authors.lastname: Niu
mesh_terms: D000701:Analgesics, Opioid / Q000008:administration & dosage* / Q000627:therapeutic use; D001784:Blood Gas Analysis; D003198:Computer Simulation; D004305:Dose-Response Relationship, Drug; D005260:Female; D005283:Fentanyl / Q000009:adverse effects / Q000493:pharmacokinetics; D006801:Humans; D006853:Hydrocodone / Q000008:administration & dosage / Q000627:therapeutic use; D007262:Infusions, Intravenous; D008297:Male; D008875:Middle Aged; D009020:Morphine / Q000008:administration & dosage / Q000627:therapeutic use; D009293:Opioid-Related Disorders / Q000150:complications* / Q000378:metabolism; D010098:Oxycodone / Q000008:administration & dosage / Q000627:therapeutic use; D010149:Postoperative Pain / Q000188:drug therapy*; D011300:Preoperative Care; D011446:Prospective Studies; D013123:Spinal Fusion
chemical_list: D000701:Analgesics, Opioid; D006853:Hydrocodone; D009020:Morphine; D010098:Oxycodone; D005283:Fentanyl