Effects of dexmedetomidine and xylazine on cardiovascular function during total intravenous anaesthesia with midazolam and ketamine and recovery quality and duration in horses
Article first published online: 15 OCT 2013
© 2013 Association of Veterinary Anaesthetists and the American College of Veterinary Anesthesia and Analgesia
Veterinary Anaesthesia and Analgesia
Volume 41, Issue 1, pages 25–35, January 2014
How to Cite
Hopster, K., Müller, C., Hopster-Iversen, C., Stahl, J., Rohn, K. and Kästner, S. (2014), Effects of dexmedetomidine and xylazine on cardiovascular function during total intravenous anaesthesia with midazolam and ketamine and recovery quality and duration in horses. Veterinary Anaesthesia and Analgesia, 41: 25–35. doi: 10.1111/vaa.12095
- Issue published online: 17 DEC 2013
- Article first published online: 15 OCT 2013
- Manuscript Accepted: 20 FEB 2013
- Manuscript Received: 3 JAN 2013
- total intravenous anaesthesia;
To compare cardiovascular effects and recovery quality and duration of total intravenous anaesthesia (TIVA) with xylazine-ketamine-midazolam or dexmedetomidine-ketamine-midazolam.
Prospective, randomized experimental cross-over trial.
Eight adult warmblood horses.
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 () were measured before treatment (baseline), after sedation (not ), 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%.
Compared to baseline, MAP did not change, while similar, but limited, decreases in HR and 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 and clinical relevance
Both drug combinations are suitable to maintain anaesthesia for two hours, with good cardiovascular and good to excellent recovery conditions.