title: Results of 24-hour ambulatory electrocardiography in dogs undergoing ovariohysterectomy following premedication with medetomidine or acepromazine.
abstract: OBJECTIVE
  To investigate heart rate characteristics in dogs undergoing ovariohysterectomy following premedication with medetomidine or acepromazine.
  
  
  METHODS
  Clinical trial.
  
  
  METHODS
  43 client-owned dogs.
  
  
  METHODS
  24-hour ambulatory electrocardiography was performed beginning approximately 1 hour prior to administration of premedications. Dogs were premedicated with medetomidine and butorphanol (n = 21) or acepromazine and butorphanol (22) and, approximately 85 minutes later, were anesthetized with propofol and isoflurane. Electrocardiographic recordings were examined to determine heart rate, cardiac conduction disturbances (ventricular premature complexes and atrioventricular block), and indices of heart rate variability (HRV).
  
  
  RESULTS
  Minimum heart rate during the 24-hour recording period was significantly lower among dogs given medetomidine than among dogs given acepromazine, but during the postoperative period, heart rate increased in all dogs as they became physically active. Intraoperative time domain HRV indices were lower and the low frequency-to-high frequency ratio was higher among dogs given acepromazine than among dogs given medetomidine; however, significant differences between groups were no longer seen by 6 hours after surgery. There was no significant difference between groups with regard to the number of ventricular premature complexes or to values of scaling exponent alpha2 (a nonlinear measure of HRV).
  
  
  CONCLUSIONS
  Results suggest that there are greater enhancements in vagally related heart rate indices in medetomidine-treated dogs that may persist until 6 hours after surgery. Despite the low heart rates, dogs given medetomidine showed expected responses to surgery and positional stimuli, and the 2 preanesthetic protocols may not result in different prevalences of ventricular premature complexes.
authors.affiliation: Department of Veterinary Clinical Sciences, Faculty of Veterinary Medicine, University of Helsinki, Helsinki, Finland.
authors.forename: Misse A M
authors.initials: MA
authors.lastname: Väisänen
authors.forename: Outi M
authors.initials: OM
authors.lastname: Vainio
authors.forename: Marja R
authors.initials: MR
authors.lastname: Raekallio
authors.forename: Heikki
authors.initials: H
authors.lastname: Hietanen
authors.forename: Heikki V
authors.initials: HV
authors.lastname: Huikuri
mesh_terms: D000075:Acepromazine / Q000494:pharmacology*; D000818:Animals; D002077:Butorphanol / Q000494:pharmacology; D004285:Dogs / Q000502:physiology* / Q000601:surgery; D018492:Dopamine Antagonists / Q000494:pharmacology*; D015716:Electrocardiography, Ambulatory / Q000379:methods / Q000662:veterinary*; D005260:Female; D006339:Heart Rate / Q000187:drug effects; D006993:Hypnotics and Sedatives / Q000494:pharmacology*; D007044:Hysterectomy / Q000662:veterinary; D007530:Isoflurane / Q000494:pharmacology; D020926:Medetomidine / Q000494:pharmacology*; D010052:Ovariectomy / Q000662:veterinary; D011184:Postoperative Period; D011229:Preanesthetic Medication / Q000379:methods / Q000662:veterinary*; D015742:Propofol / Q000494:pharmacology; D011897:Random Allocation; D013997:Time Factors
chemical_list: D018492:Dopamine Antagonists; D006993:Hypnotics and Sedatives; D000075:Acepromazine; D007530:Isoflurane; D020926:Medetomidine; D002077:Butorphanol; D015742:Propofol