Cardiopulmonary effects of two constant rate infusions of dexmedetomidine in isoflurane anaesthetized ponies
Article first published online: 17 JUN 2010
© 2010 The Authors. Journal compilation © 2010 Association of Veterinary Anaesthetists and the American College of Veterinary Anesthesiologists
Veterinary Anaesthesia and Analgesia
Volume 37, Issue 4, pages 311–321, July 2010
How to Cite
Marcilla, M. G., Schauvliege, S., Duchateau, L. and Gasthuys, F. (2010), Cardiopulmonary effects of two constant rate infusions of dexmedetomidine in isoflurane anaesthetized ponies. Veterinary Anaesthesia and Analgesia, 37: 311–321. doi: 10.1111/j.1467-2995.2010.00537.x
- Issue published online: 17 JUN 2010
- Article first published online: 17 JUN 2010
- Received 27 August 2009; accepted 27 September 2009.
- cardiac output;
- cardiopulmonary effects;
- constant rate infusion;
Objective To evaluate the cardiopulmonary effects of two different constant rate infusions (CRI) of dexmedetomidine (1 and 1.75 μg kg−1 hour−1) in experimental ponies.
Animals Six healthy ponies (mean 306 ± SD 71 kg, 7.0 ± 1.6 years).
Study design Prospective, randomized, experimental study.
Methods After premedication with intravenous (IV) dexmedetomidine (3.5 μg kg−1), anaesthesia was induced (T0) with ketamine (2.2 mg kg−1 IV) and midazolam (0.06 mg kg−1 IV) and maintained with isoflurane (Fe′ISO 1.50%) in 55% oxygen for 150 minutes. Normocapnia was maintained using artificial ventilation. Three ponies received dexmedetomidine CRIs of 1 and 1.75 μg kg−1 hour−1 from T30 to T60 and T90 to T120 respectively. In the other three ponies, the order of the doses was reversed. Continuous monitoring included pulse oximetry, electrocardiography, anaesthetic gas monitoring, arterial and central venous pressures. Cardiac ouput (LiDCO technique) was measured and arterial and venous bloods taken every 15 minutes. Cardiac index (CI), systemic vascular resistance (SVR), arterial and venous oxygen content (CaO2, CvO2) and oxygen delivery (ḊO2) were calculated. Analysis of variance with separate models for each CRI rate was used to detect differences between values obtained at the end of the CRI and their respective baseline values. A mixed model with these differences as response variable, pony as random effect and treatment and period as fixed effects was applied to find differences between the two CRIs (α = 0.05 for all analyses).
Results Heart rate (HR), CI, CaO2, CvO2 and ḊO2 decreased significantly, while significant increases were found in SVR, systolic arterial pressure and right atrial pressure with both infusion rates. No differences were found between the two dexmedetomidine CRI rates.
Conclusions and clinical relevance Although significant, cardiopulmonary effects of the dexmedetomidine CRIs in isoflurane anaesthetized ponies were small, without differences between the two dose rates.