Dexmedetomidine or Butorphanol for Co-Induction of General Anaesthesia with Propofol in Unpremedicated Healthy Dogs: Clinical and Echocardiographic Assessment.

High induction doses of propofol (PPF) may cause adverse effects. Co-induction protocols can reduce doses and enhance the beneficial profile of each drug. This study compared the induction quality, clinical, and echocardiographic effects of two rapid co-inductions in healthy, unpremedicated dogs. Baseline cardiorespiratory and echocardiographic variables were recorded. Dogs randomly received rapid intravenous PPF (2.2 mg/kg) with either dexmedetomidine (3 µg/kg) (PROPODEX; n = 12) or butorphanol (0.4 mg/kg) (PROPOBUT; n = 12). Induction quality, additional PPF dose, intubation time, cardiorespiratory parameters (2, 5, 10, 15, 20 min), and recovery quality were recorded. A second echocardiography was performed 5 min after induction. Induction quality was significantly higher in PROPODEX, with significantly lower additional PPF requirements and shorter intubation time. In PROPODEX, heart rate significantly decreased from baseline and was significantly lower than PROPOBUT, while arterial blood pressures significantly increased in PROPODEX and decreased in PROPOBUT from baseline. PROPOBUT significantly reduced left ventricular (LV) diastolic volumes and increased E/A ratio, while PROPODEX significantly increased LV systolic diameter and volumes, and significantly decreased fractional shortening. Recovery was significantly faster and better in PROPODEX. PROPOBUT preserved cardiac function but caused hypotension. PROPODEX provided superior induction and recovery quality, and cardiorespiratory stability, with only mild systolic function depression.