On the day of the study, a cephalic venous catheter was placed in each dog. The CRI dosages in this study were derived from our pilot study results. The dexmedetomidine CRI solution was made by mixing 0.2 mL of dexmedetomidine (Dexdomitor®, Zoetis Inc., Kalamazoo, MI, USA) with 9.8 mL of physiological saline, resulting in a total volume of 10 mL at a concentration of 10 μg/mL. It was administered using a Medfusion® syringe pump (Model 3500 V6, Smiths Medical, St. Paul, MN, USA).
For the atipamezole CRI solution, the total amount needed was calculated at 50 µg/kg. The calculated volume was withdrawn from the original drug solution (Antisedan®, Zoetis Inc., Kalamazoo, MI, USA) and then diluted with sterile sodium chloride 0.9% to achieve a total volume of 5ml. This volume was delivered using the Medfusion® syringe pump (Model 3500 V6, Smiths Medical, St. Paul, MN, USA) at the rate specified in the study. Both infusions were administered through an IV extension set directly attached to the preplaced IV catheter.
The awake baseline of the vital signs (see below) and EEG were recorded before the sedation started. Thereafter, the sedation procedure commenced with an initial intravenous dose of 10 μg/kg (or 60 μg/kg/h) dexmedetomidine administered over 10 min. This sedation was maintained through three decremental CRI doses, each lasting 15 min (Table 1 ). All infusions were controlled using a syringe pump, with dosages sequentially decreasing as follows: 3 μg/kg/h, 2 μg/kg/h, and finally, 1 μg/kg/h. The complete duration of the study when dexmedetomidine was administered was 55 min. Following the last dexmedetomidine CRI administration, the dogs promptly received atipamezole treatment through an intravenous dose of 50 μg/kg administered over 5 min (or 600 μg/kg/h).
The treatment protocol and timeline details are provided inTable 1 , in addition to the continuous collection of EEG data every 2 s by the EEG monitor throughout the entire experiment. Analgesic properties were assessed (see below) by application of noxious stimuli (NOX) as indicated in Table 1 . Furthermore, cardiorespiratory assessments were conducted at intervals of every 3 min within each phase of the experiment.
For the atipamezole CRI solution, the total amount needed was calculated at 50 µg/kg. The calculated volume was withdrawn from the original drug solution (Antisedan®, Zoetis Inc., Kalamazoo, MI, USA) and then diluted with sterile sodium chloride 0.9% to achieve a total volume of 5ml. This volume was delivered using the Medfusion® syringe pump (Model 3500 V6, Smiths Medical, St. Paul, MN, USA) at the rate specified in the study. Both infusions were administered through an IV extension set directly attached to the preplaced IV catheter.
The awake baseline of the vital signs (see below) and EEG were recorded before the sedation started. Thereafter, the sedation procedure commenced with an initial intravenous dose of 10 μg/kg (or 60 μg/kg/h) dexmedetomidine administered over 10 min. This sedation was maintained through three decremental CRI doses, each lasting 15 min (
The treatment protocol and timeline details are provided in
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