title: Low-dose remifentanil to suppress haemodynamic responses to noxious stimuli in cardiac surgery: a dose-finding study.
abstract: BACKGROUND
  High-dose remifentanil (1-5 microg kg-1 min-1), commonly used for cardiac surgery, has been associated with muscle rigidity, hypotension, bradycardia, and reduced cardiac output. The aim of this study was to determine an optimal lower remifentanil dose, which should be accompanied by fewer adverse events, that still effectively suppresses haemodynamic responses to typical stressful stimuli (i.e. intubation, skin incision, and sternotomy).
  
  
  METHODS
  Total i.v. anaesthesia consisted of a target-controlled propofol (2 microg ml-1) and a remifentanil infusion. Forty patients were allocated to receive either a constant infusion of remifentanil at 0.1 microg kg-1 min-1 or up-titrations to 0.2, 0.3, or 0.4 microg kg-1 min-1, respectively, 5 min before each stimulus. Subsequently, changes in heart rate and mean arterial blood pressure were recorded for 8 min. Increases exceeding 20% of baseline were considered to be of clinical relevance. Patients who exhibited these alterations were termed responders.
  
  
  RESULTS
  The number of responders was less with the two higher remifentanil dosages (P<0.05) while propofol target doses could either be kept at the same level or even be reduced without affecting the plane of anaesthesia. Although single phenylephrine bolus had to be applied more frequently in these two groups (P<0.05), no severe haemodynamic depression was observed.
  
  
  CONCLUSIONS
  Remifentanil at 0.3 and 0.4 microg kg-1 min-1 in combination with a target-controlled propofol infusion in the pre-bypass period is well tolerated. It appears to mitigate potentially hazardous haemodynamic responses from stressful stimuli equally well as higher doses when compared with data from the literature.
authors.affiliation: Division of Cardiothoracic and Vascular Anaesthesia and Intensive Care, University Hospital Vienna, Vienna, Austria. barbara.steinlechner@meduniwien.ac.at
authors.forename: B
authors.initials: B
authors.lastname: Steinlechner
authors.forename: M
authors.initials: M
authors.lastname: Dworschak
authors.forename: B
authors.initials: B
authors.lastname: Birkenberg
authors.forename: T
authors.initials: T
authors.lastname: Lang
authors.forename: A
authors.initials: A
authors.lastname: Schiferer
authors.forename: A
authors.initials: A
authors.lastname: Moritz
authors.forename: B
authors.initials: B
authors.lastname: Mora
authors.forename: A
authors.initials: A
authors.lastname: Rajek
mesh_terms: D000368:Aged; D000701:Analgesics, Opioid / Q000008:administration & dosage*; D018686:Anesthetics, Intravenous / Q000008:administration & dosage; D001794:Blood Pressure / Q000187:drug effects; D002302:Cardiac Output / Q000187:drug effects*; D006348:Cardiac Surgical Procedures; D062109:Dermatologic Surgical Procedures; D004305:Dose-Response Relationship, Drug; D004334:Drug Administration Schedule; D004562:Electrocardiography / Q000187:drug effects; D005260:Female; D006339:Heart Rate / Q000187:drug effects; D006801:Humans; D007442:Intubation, Intratracheal; D008297:Male; D008875:Middle Aged; D016343:Monitoring, Intraoperative / Q000379:methods; D010880:Piperidines / Q000008:administration & dosage*; D015742:Propofol / Q000008:administration & dosage; D000077208:Remifentanil; D013249:Sternum / Q000601:surgery; D013312:Stress, Physiological / Q000503:physiopathology / Q000517:prevention & control
chemical_list: D000701:Analgesics, Opioid; D018686:Anesthetics, Intravenous; D010880:Piperidines; D000077208:Remifentanil; D015742:Propofol