title: Effect of remifentanil infusion rate on stress response to the pre-bypass phase of paediatric cardiac surgery.
abstract: BACKGROUND
  Opioids are used routinely to eliminate the stress response in the pre-bypass phase of paediatric cardiac surgery. Remifentanil is a unique opioid allowing a rapidly titratable effect. No data are available regarding a suitable remifentanil dose regimen for obtunding stress and cardiovascular responses to such surgery.
  
  
  METHODS
  We recruited 49 infants and children under 5 yr old who were randomized to receive one of four remifentanil infusion rates (0.25, 1.0, 2.5, or 5.0 micro g kg(-1) min(-1)). Blood samples were obtained at induction, pre-surgery, 5 min after opening the chest, and immediately pre-bypass. Whole blood glucose was measured at all time points while cortisol and neuropeptide Y (NPY) were measured in the first and last samples. Heart rate and arterial pressure were also recorded.
  
  
  RESULTS
  There was a significant increase in whole blood glucose 5 min after opening the chest and pre-bypass (P=0.009, P=0.002) in patients receiving remifentanil 0.25 micro g kg(-1) min(-1), but not in those receiving higher doses. Increased remifentanil dosage was associated with reduced plasma cortisol during surgery (P<0.001). Baseline NPY showed considerable variation and there was no association between pre-bypass NPY and remifentanil dose. There was a significantly higher heart rate at the pre-bypass stage of surgery in the remifentanil 0.25 micro g kg(-1) min(-1) group compared with higher doses (P=0.0006). Four out of five neonates with complex cardiac conditions showed severe bradycardia associated with remifentanil.
  
  
  CONCLUSIONS
  In infants and children under 5 yr, remifentanil infusions of 1.0 micro g kg(-1) min(-1) and greater can suppress the glucose increase and tachycardia associated with the pre-bypass phase of cardiac surgery, while 0.25 micro g kg(-1) min(-1) does not. Remifentanil should be used with caution in neonates with complex congenital heart disease.
authors.affiliation: University Department of Anaesthesia, Bristol Royal Infirmary, Upper Maudlin Street, Bristol BS2 8HW, UK.
authors.forename: N K
authors.initials: NK
authors.lastname: Weale
authors.forename: C A
authors.initials: CA
authors.lastname: Rogers
authors.forename: R
authors.initials: R
authors.lastname: Cooper
authors.forename: J
authors.initials: J
authors.lastname: Nolan
authors.forename: A R
authors.initials: AR
authors.lastname: Wolf
mesh_terms: D000701:Analgesics, Opioid / Q000008:administration & dosage*; D001786:Blood Glucose / Q000187:drug effects / Q000378:metabolism; D001794:Blood Pressure / Q000187:drug effects; D002675:Child, Preschool; D004305:Dose-Response Relationship, Drug; D004311:Double-Blind Method; D004334:Drug Administration Schedule; D005260:Female; D006330:Heart Defects, Congenital / Q000601:surgery*; D006339:Heart Rate / Q000187:drug effects; D006801:Humans; D006854:Hydrocortisone / Q000097:blood; D007223:Infant; D008297:Male; D009478:Neuropeptide Y / Q000097:blood; D010880:Piperidines / Q000008:administration & dosage*; D011446:Prospective Studies; D000077208:Remifentanil; D013312:Stress, Physiological / Q000517:prevention & control*
chemical_list: D000701:Analgesics, Opioid; D001786:Blood Glucose; D009478:Neuropeptide Y; D010880:Piperidines; D000077208:Remifentanil; D006854:Hydrocortisone