title: Remifentanil requirements during propofol administration to block the somatic response to skin incision in children and adults.
abstract: BACKGROUND
  During sevoflurane administration, children require a remifentanil infusion rate twofold higher than adults to block responses to skin incision. Similar data concerning remifentanil requirements are unavailable during total IV anesthesia.
  
  
  METHODS
  We prospectively determined the infusion rate (IR) of remifentanil necessary to block the somatic response to skin incision in 50% (IR50) of adults (n = 20, aged 20-60 yr) and children (n = 20, aged 3-11 yr) during propofol anesthesia. In each patient undergoing lower abdominal surgery, a remifentanil infusion was initiated, followed by target-controlled infusion of propofol set at a plasma concentration of 6 mug/mL. After tracheal intubation, propofol was reduced to 3 microg/mL until the end of the study. Remifentanil IR was determined according to Dixon's up-and-down method, with the first patient in each group receiving 0.2 microg x kg(-1) x min(-1) followed by the consecutive patient receiving 0.02 microg x kg(-1) x min(-1) modifications according to the response of the previous patient. The remifentanil IR was kept unchanged for at least 20 min before surgery. At the beginning of surgery, only the skin incision was performed, and the somatic response was observed. If there was any gross movement of extremity the response was considered positive.
  
  
  RESULTS
  The IR50 (CI(95%)) was 0.08 (0.06-0.12) microg x kg(-1) x min(-1) in adults and 0.15 (0.13-0.17) microg x kg(-1) x min(-1) in children (P < 0.001).
  
  
  CONCLUSIONS
  These results demonstrate that, similar to sevoflurane anesthesia, during total IV anesthesia with propofol, children require a remifentanil IR almost twofold higher than adults to block the somatic response to skin incision.
authors.affiliation: Departamento de Anestesiología, Facultad de Medicina, Pontificia Universidad Católica de Chile, Santiago, Chile. hmunoz@med.puc.cl
authors.forename: Hernán R
authors.initials: HR
authors.lastname: Muñoz
authors.forename: Luis I
authors.initials: LI
authors.lastname: Cortínez
authors.forename: Mauricio E
authors.initials: ME
authors.lastname: Ibacache
authors.forename: Fernando R
authors.initials: FR
authors.lastname: Altermatt
mesh_terms: D000328:Adult; D000701:Analgesics, Opioid / Q000627:therapeutic use*; D018686:Anesthetics, Intravenous / Q000627:therapeutic use*; D002648:Child; D002675:Child, Preschool; D062109:Dermatologic Surgical Procedures; D005260:Female; D006801:Humans; D007262:Infusions, Intravenous; D008297:Male; D008875:Middle Aged; D016343:Monitoring, Intraoperative; D010880:Piperidines / Q000008:administration & dosage / Q000627:therapeutic use*; D015742:Propofol / Q000627:therapeutic use*; D000077208:Remifentanil; D012867:Skin / Q000187:drug effects*
chemical_list: D000701:Analgesics, Opioid; D018686:Anesthetics, Intravenous; D010880:Piperidines; D000077208:Remifentanil; D015742:Propofol