title: Effects of dexmedetomidine and xylazine on cardiovascular function during total intravenous anaesthesia with midazolam and ketamine and recovery quality and duration in horses.
abstract: OBJECTIVE
  To compare cardiovascular effects and recovery quality and duration of total intravenous anaesthesia (TIVA) with xylazine-ketamine-midazolam or dexmedetomidine-ketamine-midazolam.
  
  
  METHODS
  Prospective, randomized experimental cross-over trial.
  
  
  METHODS
  Eight adult warmblood horses.
  
  
  METHODS
  After sedation with acepromazine and either xylazine [0.5 mg kg(-1) , intravenously (IV)] or dexmedetomidine (3.5 μg kg(-1) IV) anaesthesia was induced with ketamine and midazolam and maintained with a constant rate infusion (CRI) of xylazine (1 mg kg(-1)  hour(-1) ) [XKM] or dexmedetomidine (7 μg kg(-1)  hour(-1) ) [DKM] in combination with midazolam (0.1 mg kg(-1)  hour(-1) ), and ketamine infusion (initially 3 mg kg(-1)  hour(-1) ) for 120 minutes. Ketamine infusion rate was increased in response to positive reactions to electrical nociceptive stimulation performed every 30 minutes. Heart rate (HR), mean arterial blood pressure (MAP) and cardiac output (Q˙t) were measured before treatment (baseline), after sedation (not Q˙t), and during anaesthesia. Xylazine, dexmedetomidine, midazolam and ketamine kinetics were calculated, from plasma drug concentrations. Twenty minutes after end of TIVA, flumazenil (0.01 mg kg(-1) IV) was administered. Recovery quality and duration were assessed. Two-way analysis of variance with repeated measurements or Wilcoxon signed rank test as relevant were used to analyse data with an alpha of 5%.
  
  
  RESULTS
  Compared to baseline, MAP did not change, while similar, but limited, decreases in HR and Q˙t were observed in both TIVA's. Mean ketamine doses of 3.7 mg kg(-1)  hour(-1) were required with both treatments. Plasma concentrations of dexmedetomidine and xylazine showed high intra- and inter-individual changes with elimination half-lifes of 46 ± 7 minutes and 64 ± 13 minutes, respectively. Recovery quality was good to excellent with mean duration of 37 ± 16 and 46 ± 21 minutes after stopping TIVA with XKM and DKM, respectively.
  
  
  CONCLUSIONS
  Both drug combinations are suitable to maintain anaesthesia for two hours, with good cardiovascular and good to excellent recovery conditions.
authors.affiliation: Equine Clinic, University of Veterinary Medicine Hanover, Foundation, Hanover, Germany.
authors.forename: Klaus
authors.initials: K
authors.lastname: Hopster
authors.forename: Christina
authors.initials: C
authors.lastname: Müller
authors.forename: Charlotte
authors.initials: C
authors.lastname: Hopster-Iversen
authors.forename: Jessica
authors.initials: J
authors.lastname: Stahl
authors.forename: Karl
authors.initials: K
authors.lastname: Rohn
authors.forename: Sabine
authors.initials: S
authors.lastname: Kästner
mesh_terms: D000762:Anesthesia Recovery Period; D000778:Anesthetics, Dissociative / Q000008:administration & dosage / Q000494:pharmacology*; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects*; D018592:Cross-Over Studies; D020927:Dexmedetomidine / Q000008:administration & dosage / Q000494:pharmacology; D004359:Drug Therapy, Combination; D006339:Heart Rate / Q000187:drug effects*; D006736:Horses; D006993:Hypnotics and Sedatives / Q000008:administration & dosage / Q000494:pharmacology*; D007649:Ketamine / Q000008:administration & dosage / Q000494:pharmacology; D008874:Midazolam / Q000008:administration & dosage / Q000494:pharmacology; D013997:Time Factors; D014991:Xylazine / Q000008:administration & dosage / Q000494:pharmacology
chemical_list: D000778:Anesthetics, Dissociative; D006993:Hypnotics and Sedatives; D014991:Xylazine; D020927:Dexmedetomidine; D007649:Ketamine; D008874:Midazolam
keywords: dexmedetomidine; flumazenil; ketamine; midazolam; total intravenous anaesthesia; xylazine