title: Preoperative dexmedetomidine attenuates hemodynamic responses to hydrodissection in patients undergoing robotic thyroidectomy.
abstract: OBJECTIVE
  Percutaneous tunneling (hydrodissection) in the neck and anterior chest in patients undergoing robotic thyroidectomy leads to significant hemodynamic responses such as increases in blood pressure and heart rate. We evaluated whether a single preoperative dexmedetomidine injection attenuated hemodynamic responses to hydrodissection by reducing the half-maximal effective concentration (EC50) of remifentanil needed to maintain hemodynamic stability during hydrodissection.
  
  
  METHODS
  Forty-one patients undergoing robot-assisted endoscopic thyroidectomy were randomly allocated to one of the two groups-group D (n = 22) and group C (n = 19) patients received dexmedetomidine 1 µg/kg and normal saline for 10 min before anesthetic induction, respectively. The EC50 of remifentanil for hemodynamic stability during hydrodissection was determined using Dixon's up-and-down method with initial dose (4 and 5 ng/mL in groups D and C, respectively). The concentration of remifentanil for consecutive patients in each group was determined by the response of the previous patient, using increments or decrements of 0.5 ng/mL. Hemodynamic stability during hydrodissection was defined as increased systolic blood pressure <20 % of baseline.
  
  
  RESULTS
  The EC50 of remifentanil for maintaining hemodynamic stability during hydrodissection was 0.8 ng/mL in group D and 7.3 ng/mL in group C (p = 0.002).
  
  
  CONCLUSIONS
  A single preoperative dexmedetomidine injection attenuated hydrodissection-induced hemodynamic responses in patients undergoing robotic thyroidectomy.
authors.affiliation: Department of Anesthesiology and Pain Medicine, Hallym University Medical Center, Anyang, South Korea.
authors.forename: Mae-Hwa
authors.initials: MH
authors.lastname: Kang
authors.forename: Ho-Jin
authors.initials: HJ
authors.lastname: Lee
authors.forename: Young-Jin
authors.initials: YJ
authors.lastname: Lim
authors.forename: Young-Tae
authors.initials: YT
authors.lastname: Jeon
authors.forename: Jung-Won
authors.initials: JW
authors.lastname: Hwang
authors.forename: Hee-Pyoung
authors.initials: HP
authors.lastname: Park
mesh_terms: D058647:Adrenergic alpha-2 Receptor Agonists / Q000627:therapeutic use*; D000328:Adult; D000771:Anesthesia, Intravenous / Q000009:adverse effects / Q000379:methods; D018686:Anesthetics, Intravenous; D020927:Dexmedetomidine / Q000627:therapeutic use*; D004311:Double-Blind Method; D005260:Female; D006439:Hemodynamics / Q000187:drug effects*; D006801:Humans; D008297:Male; D008875:Middle Aged; D019990:Perioperative Care / Q000379:methods*; D010880:Piperidines; D015742:Propofol; D011446:Prospective Studies; D000077208:Remifentanil; D012371:Robotics; D013965:Thyroidectomy / Q000009:adverse effects*; D055815:Young Adult
chemical_list: D058647:Adrenergic alpha-2 Receptor Agonists; D018686:Anesthetics, Intravenous; D010880:Piperidines; D020927:Dexmedetomidine; D000077208:Remifentanil; D015742:Propofol