Effect of dexmedetomidine vs. acepromazine-methadone premedication on limb to lung circulation time in dogs.

摘要

The study compared limb-to-lung circulation times (CT) in dogs under general anaesthesia after premedication with dexmedetomidine (DEX) or acepromazine-methadone (ACE-M). Healthy male and female dogs (n=20) were randomly assigned to receive acepromazine 0.04 mg/kg and methadone 0.2 mg/kg intramuscularly (IM), or DEX 0.01 mg/kg IM. Anesthesia was induced with propofol and maintained with isoflurane at similar concentration in both groups. Mechanical ventilation was started immediately (20 breaths/min; inspiratory to expiratory ratio 1:2) and tidal volume was adjusted to achieve an end-tidal CO₂ concentration (PE'CO₂) of between 3.9 and 5.3 kPa. Ten minutes later arterial blood gas was analyzed and baseline data recorded for 3 minutes. A single dose of sodium bicarbonate 0,5 mEq/kg was administered intravenously over 10 s starting with inspiration. Limb-to-lung CT was defined as the time interval between the start of bicarbonate injection and the recording of the highest PE'CO₂. Following bicarbonate administration, PE'CO2 increased, and then rapidly decreased to baseline in both groups. CT was shorter in the ACE-M group (20+or-2.3 vs. 27+or-5.1 s). Bodyweight was higher in the ACE-M group (30.6+or-3.9 vs. 23.3+or-6.8 kg). Mean arterial blood pressure was higher in the DEX group (92+or-9 vs. 73+or-7 mm Hg) but premedication with DEX significantly prolonged CT compared to premedication with ACE-M.