title: Dexmedetomidine infusion as a supplement to isoflurane anaesthesia for vitreoretinal surgery.
abstract: BACKGROUND
  We explored the sympatholytic property of dexmedetomidine, especially its role in intraocular pressure (IOP) reduction, haemodynamic stability, and attenuation of extubation response.
  
  
  METHODS
  In this double-blind, randomized, controlled trial approved by the Hospital Ethics Committee, 60 patients undergoing elective vitreoretinal surgery were allocated to two groups, receiving either placebo or dexmedetomidine. A loading dose of dexmedetomidine 2.5 microg kg(-1) h(-1) (or placebo in same volume) was infused for 10 min immediately before induction of anaesthesia with propofol, followed by a maintenance dexmedetomidine or placebo infusion at 0.4 microg kg(-1) h(-1) till 30 min before the end of the operation. Anaesthesia was maintained with isoflurane, oxygen, and air mixture. IOP was measured before the loading dose and 1 min after tracheal intubation. The mean arterial pressure (MAP) and heart rate (HR) during loading, induction, maintenance, extubation, and recovery period were measured. The degree of strain on extubation was graded from 0 to 5.
  
  
  RESULTS
  The use of vasopressor/labetalol/atropine and the reduction in IOP were comparable between the two groups. There was a significant variation in MAP and HR over time within group, but not between groups. The median degree of strain was significantly lower (P = 0.049), and the time to reach Aldrete score of 10 shorter (P = 0.031) in the dexmedetomidine group.
  
  
  CONCLUSIONS
  Dexmedetomidine can be used without undue haemodynamic fluctuation and can decrease the excitatory response during extubation. The reduction in IOP with dexmedetomidine was comparable with placebo.
authors.affiliation: Department of Anaesthesia, Queen Elizabeth Hospital, Hong Kong, China. syylee321@yahoo.com.hk
authors.forename: Y Y S
authors.initials: YY
authors.lastname: Lee
authors.forename: S M
authors.initials: SM
authors.lastname: Wong
authors.forename: C T
authors.initials: CT
authors.lastname: Hung
mesh_terms: D000759:Adjuvants, Anesthesia / Q000494:pharmacology; D000316:Adrenergic alpha-Agonists / Q000494:pharmacology*; D000328:Adult; D000762:Anesthesia Recovery Period; D018685:Anesthetics, Inhalation; D001794:Blood Pressure / Q000187:drug effects; D020878:Device Removal; D020927:Dexmedetomidine / Q000494:pharmacology*; D004311:Double-Blind Method; D005260:Female; D006801:Humans; D007429:Intraocular Pressure / Q000187:drug effects; D007442:Intubation, Intratracheal; D007530:Isoflurane; D008297:Male; D008875:Middle Aged; D012160:Retina / Q000601:surgery*; D014822:Vitreous Body / Q000601:surgery*
chemical_list: D000759:Adjuvants, Anesthesia; D000316:Adrenergic alpha-Agonists; D018685:Anesthetics, Inhalation; D020927:Dexmedetomidine; D007530:Isoflurane