ABSTRACT:
This study compared cardiovascular and respiratory effects of dexmedetomidine and xylazine in total intravenous anesthesia with propofol, ketamine, and lidocaine. Twenty-one female dogs were submitted to ovariohysterectomy, premedicated with acepromazine and anesthetized with propofol at a variable rate. The dogs were intubated and supplemented with 100% oxygen in a circuit without rebreathing gases in spontaneous ventilation. They were divided into three groups (n=21) after induction: control (CON) with ketamine (2 mg/kg + 0.6 mg/kg/h) and lidocaine (2 mg/kg + 3 mg/kg/h), DEX and XIL with the same drugs as CON, associated with dexmedetomidine (2 µg/kg + 1 µg/kg/h) or xylazine (0.2 mg/kg + 0.1 mg/kg/h). Propofol consumption, fentanyl analgesic rescue, and cardiorespiratory and blood gas parameters were evaluated during anesthesia. The DEX group had a lower consumption of propofol (0.16 ± 0.09 mg/kg/min) compared to CON (0.24 ± 0.09 mg/kg/min), both not differing from XIL (0.23 ± 0.09 mg/kg/min). The mean arterial pressure was higher after the initial bolus in DEX (107 ± 8 mmHg) and XIL (96 ± 11 mmHg) compared to the CON group (80 ± 10 mmHg). Higher accumulation of arterial carbon dioxide and a decrease in pH were observed in the CON group. The total number of fentanyl rescues did not differ between DEX (7) and XIL (6) and were lower than CON (16). Therefore, dexmedetomidine and xylazine reduced intraoperative fentanyl consumption compared to ketamine and lidocaine infusion alone. However, only dexmedetomidine promoted lower propofol consumption and higher blood pressure values.
Key words:
infusion rate; alpha-2 adrenergic agonists; analgesia; sparing effect; neutering
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