title: Spontaneous ventilation with remifentanil in children.
abstract: BACKGROUND
  Remifentanil is a short-acting drug that allows us to study the specific respiratory effects of potent opioid analgesics. The purpose of this study is to describe the effects of a remifentanil infusion during spontaneous ventilation in children. Pharmacokinetic studies provide useful information on the time course of opioid blood concentrations; however, they cannot be easily translated into infusion administration guidelines for pediatric clinical practice.
  
  
  METHODS
  A total of 32 children, aged 2-7 years, undergoing restorative dentistry, spontaneously breathing under sevoflurane anesthesia were enrolled in the study. After an initial bolus dose of remifentanil, an infusion was administered in ascending logarithmic increments at 10 min intervals. Increments were discontinued when endtidal carbon dioxide exceeded 9 kPa (70 mmHg), desaturation occurred (SpO2 < 94%) or with the onset of apnea (>5 s). The maximum tolerated dose was determined for each subject. Endtidal carbon dioxide, minute ventilation and respiratory rate were continuously recorded.
  
  
  RESULTS
  The median tolerated dose of remifentanil was 0.127 microg.kg(-1).min(-1) (range: 0.053-0.3 microg.kg(-1).min(-1)). When comparing the last four incremental increases in each subject, 35% change in respiratory rate occurred in the last 10 min period while changes in endtidal carbon dioxide and minute ventilation were gradual and of less magnitude. There was no correlation between age and respiratory rate.
  
  
  CONCLUSIONS
  There is a large variation in the dose of remifentanil tolerated by children while breathing spontaneously under anesthesia. A respiratory rate of <10 b.min(-1) appears to be the best predictor of the maximum tolerated dose.
authors.affiliation: Department of Anesthesia, British Columbia Children's Hospital, University of British Columbia, BC, Canada. anserminos@yahoo.ca
authors.forename: J Mark
authors.initials: JM
authors.lastname: Ansermino
authors.forename: Peter
authors.initials: P
authors.lastname: Brooks
authors.forename: David
authors.initials: D
authors.lastname: Rosen
authors.forename: Christine A
authors.initials: CA
authors.lastname: Vandebeek
authors.forename: Clayton
authors.initials: C
authors.lastname: Reichert
mesh_terms: D000701:Analgesics, Opioid / Q000493:pharmacokinetics*; D001049:Apnea / Q000139:chemically induced; D002245:Carbon Dioxide / Q000378:metabolism; D002648:Child; D002675:Child, Preschool; D003814:Dentistry, Operative / Q000379:methods; D004305:Dose-Response Relationship, Drug; D005260:Female; D006801:Humans; D008297:Male; D010880:Piperidines / Q000493:pharmacokinetics*; D000077208:Remifentanil; D012119:Respiration / Q000187:drug effects*; D012737:Sex Factors; D013997:Time Factors
chemical_list: D000701:Analgesics, Opioid; D010880:Piperidines; D002245:Carbon Dioxide; D000077208:Remifentanil