Cardiorespiratory effects of intravenous morphine, xylazine and atropine in dogs

The IV injection of xylazine (0.4 mg kg−1), morphine (0.4 mg kg−1) and atropine (0.02 mg kg−1) is frequently used to provide short‐term sedation and analgesia for canine patients at our hospital. The purpose of the present investigation was to assess the cardiopulmonary effects of this combination. Six hound dogs (weight 27 ± 3 kg) had the skin over the ventral neck and dorsal metatarsus surgically prepared and anesthetized with lidocaine. Central venous and arterial catheters were percutaneously placed into the jugular vein and dorsal pedal artery, respectively. Baseline measurements of respiratory rate (RR), heart rate (HR), rectal temperature, direct systemic arterial pressure (SAP, MAP, DAP), central venous pressure (CVP), and arterial blood gas analysis were obtained. The 2‐D, M‐mode, and Doppler echocardiography were used to obtain or calculate fractional shortening and cardiac output. Level of alertness and resistance to handling were quantified on an analog scale. The drug mixture was given, and measurements repeated at 5, 15, 30, and 60 minutes. A repeated measures anova was used to detect differences over time, and Dunnett's test was used for multiple comparisons when significance was reached (p