title: Evaluation of the sedative and cardiovascular effects of intramuscular administration of dexmedetomidine with and without concurrent atropine administration in dogs.
abstract: OBJECTIVE
  To evaluate degree of sedation and cardiovascular, respiratory, acid-base excess, and electrolyte variables in response to IM administration of dexmedetomidine or dexmedetomidine with atropine.
  
  
  METHODS
  Randomized crossover study. Animals-5 healthy 1- to 2-year-old sexually intact male Treeing Walker Coonhounds.
  
  
  METHODS
  Dogs were instrumented with catheters placed in the dorsal pedal artery and lateral saphenous vein. All dogs received dexmedetomidine (10 μg/kg [4.5 μg/lb], IM) or dexmedetomidine with atropine (0.02 mg/kg [0.009 mg/lb], IM). Variables were measured at baseline (time 0) and 5, 15, 30, and 60 minutes after drug administration.
  
  
  RESULTS
  In all dogs, lithium dilution cardiac output decreased from a mean ± SD baseline value of 5.07 ± 1.0 L/min to 2.1 ± 0.9 L/min. Cardiac output was not different between dexmedetomidine group dogs and dexmedetomidine-atropine group dogs. Mean arterial pressure increased from baseline in both groups but was significantly higher in dexmedetomidine-atropine group dogs, compared with dexmedetomidine group dogs. Heart rate in dexmedetomidine group dogs decreased from 110 ± 14.2 beats/min to 49.4 ± 10.4 beats/min by 15 minutes. No differences were seen in blood gas values, electrolyte concentration, or hemoglobin values over time or between groups. Arrhythmias were detected in dexmedetomidine-atropine group dogs and included atrioventricular block, ventricular premature contractions, and ventricular bigeminy.
  
  
  CONCLUSIONS
  Administration of atropine at 0.02 mg/kg, IM, with dexmedetomidine at 10 μg/kg, IM, resulted in an increase in mean arterial blood pressure and heart rate; deleterious cardiac arrhythmias were also observed. Use of atropine with dexmedetomidine is not recommended in dogs.
authors: Department of Clinical Sciences, College of Veterinary Medicine and Biological Sciences, Colorado State University, Fort Collins, CO 80523, USA. jcongdon@colostate.edu
authors: Jonathan M
authors: JM
authors: Congdon
authors: Megan
authors: M
authors: Marquez
authors: Sirirat
authors: S
authors: Niyom
authors: Pedro
authors: P
authors: Boscan
mesh_terms: D000818:Animals; D001145:Arrhythmias, Cardiac / Q000139:chemically induced / Q000662:veterinary; D001285:Atropine / Q000008:administration & dosage / Q000494:pharmacology*; D001794:Blood Pressure / Q000187:drug effects; D001831:Body Temperature; D002302:Cardiac Output / Q000187:drug effects; D018592:Cross-Over Studies; D020927:Dexmedetomidine / Q000008:administration & dosage / Q000494:pharmacology*; D004283:Dog Diseases / Q000139:chemically induced; D004285:Dogs; D004359:Drug Therapy, Combination; D006339:Heart Rate / Q000187:drug effects; D006993:Hypnotics and Sedatives / Q000008:administration & dosage / Q000494:pharmacology*; D008297:Male; D012119:Respiration / Q000187:drug effects
chemical_list: D006993:Hypnotics and Sedatives; D020927:Dexmedetomidine; D001285:Atropine