title: Cardiopulmonary effects of an infusion of remifentanil or morphine in horses anesthetized with isoflurane and dexmedetomidine.
abstract: OBJECTIVE
  To examine the cardiopulmonary effects of infusions of remifentanil or morphine, and their influence on recovery of horses anesthetized with isoflurane and dexmedetomidine.
  
  
  METHODS
  Randomized crossover study with 7-day rest periods.
  
  
  METHODS
  Six adult horses (507 ± 61 kg).
  
  
  METHODS
  After the horses were sedated with xylazine, anaesthesia was induced with ketamine and diazepam, and maintained with isoflurane. After approximately 60 minutes, a dexmedetomidine infusion was started (0.25 μg kg(-1) then 1.0 μg(-1) kg(-1) hour(-1) ) in combination with either saline (group S), morphine (0.15 mg kg(-1) then 0.1 mg kg(-1) hour(-1) ; group M), or remifentanil (6.0 μg kg(-1) hour(-1) ; group R) for 60 minutes. Mean arterial pressure, heart rate, end-tidal carbon dioxide tension, and end-tidal isoflurane concentration were recorded every 5 minutes. Core body temperature, cardiac output, right ventricular and arterial blood-gas values were measured every 15 minutes. Cardiac index, systemic vascular resistance (SVR), intrapulmonary shunt fraction, alveolar dead space, oxygen delivery and extraction ratio were calculated. Recoveries were videotaped and scored by two observers blinded to the treatment. Data were analyzed using repeated measures anova followed by Dunnett's or Bonferroni's significant difference test. Recovery scores were analyzed using a Kruskal-Wallis test.
  
  
  RESULTS
  No significant differences were found among groups. Compared to baseline, heart rate decreased and SVR increased significantly in all groups, and cardiac index significantly decreased in groups S and M. Hemoglobin concentration, oxygen content and oxygen delivery significantly decreased in all groups. The oxygen extraction ratio significantly increased in groups M and R. Lactate concentration significantly increased in group S. Recovery scores were similar among groups.
  
  
  CONCLUSIONS
  Dexmedetomidine alone or in combination with remifentanil or morphine infusions was infused for 60 minutes without adverse effects in the 6 healthy isoflurane-anesthetized horses in this study.
authors.affiliation: Department of Small Animal Clinical Sciences, Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, SK, Canada.
authors.forename: Perrine
authors.initials: P
authors.lastname: Benmansour
authors.forename: Michelle L
authors.initials: ML
authors.lastname: Husulak
authors.forename: José L
authors.initials: JL
authors.lastname: Bracamonte
authors.forename: Shannon G
authors.initials: SG
authors.lastname: Beazley
authors.forename: Elanor
authors.initials: E
authors.lastname: Withnall
authors.forename: Tanya
authors.initials: T
authors.lastname: Duke-Novakovski
mesh_terms: D018712:Analgesics, Non-Narcotic / Q000008:administration & dosage / Q000494:pharmacology; D000701:Analgesics, Opioid / Q000008:administration & dosage / Q000494:pharmacology; D000762:Anesthesia Recovery Period; D018685:Anesthetics, Inhalation / Q000008:administration & dosage / Q000494:pharmacology; D000818:Animals; D001784:Blood Gas Analysis; D001794:Blood Pressure / Q000187:drug effects; D001831:Body Temperature; D018592:Cross-Over Studies; D020927:Dexmedetomidine / Q000008:administration & dosage / Q000494:pharmacology*; D004359:Drug Therapy, Combination; D005260:Female; D006339:Heart Rate / Q000187:drug effects; D006736:Horses; D007530:Isoflurane / Q000008:administration & dosage / Q000494:pharmacology*; D008297:Male; D009020:Morphine / Q000008:administration & dosage / Q000494:pharmacology*; D010880:Piperidines / Q000008:administration & dosage / Q000494:pharmacology*; D000077208:Remifentanil
chemical_list: D018712:Analgesics, Non-Narcotic; D000701:Analgesics, Opioid; D018685:Anesthetics, Inhalation; D010880:Piperidines; D020927:Dexmedetomidine; D009020:Morphine; D007530:Isoflurane; D000077208:Remifentanil
keywords: cardiopulmonary effects; dexmedetomidine; horse; partial intravenous anaesthesia; recovery; remifentanil