The cardiopulmonary effects of romifidine in dogs with and without glycopyrrolate treatment

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Sinclair, Melissa D.
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University of Guelph

The cardiopulmonary and electrocardiographic effects of high and low dose romifidine (RO) in dogs with and without glycopyrrolate pre-medication (p), and with concurrent (c) glycopyrrolate administration were investigated using thermodilution catheterization and echocardiography in two separate experiments. Six healthy adult mixed breed dogs (mean ± SD, 23 ± 2.4 kg) received each treatment in a randomized cross over design during each experimental phase. Glycopyrrolate (Gp) 0.01 mg/kg, or saline (Sp) 0.5 mL, were administered intramuscularly as pre-medication, or glycopyrrolate was administered concurrently (Gc) with RO. Romidifine was administered subcutaneously at low (40 [mu]g/kg) or high (120 [mu]g/kg) dosages. Treatment groups were as follows: T1, Sp + RO (40 [mu]g/kg); T2, Gp + RO (40 [mu]g/kg); T3, Sp + RO (120 [mu]g/kg); T4, Gp + RO (120 [mu]g/kg); T5, Sp + Gp + RO (120 [mu]g/kg). Measurements were repeated 15 minutes after Gp or Sp (time -5, RO or RO + Gc was administrated 20 minutes after pre-medication (time 0). Further measurements were taken at 10, 20, 30, 60, and 90 minutes after RO administration. In the thermodilution phase, anesthesia was mask induced and maintained with isoflurane for cardiopulmonary instrumentation. Dogs were acclimatized for at least 30 minutes after recovery from anesthesia, baseline measurements were recorded and one of the five treatments administered. A continuous lead II ECG, arterial and mixed venous blood gases, heart rate (HR), respiratory rate (RR), temperature, cardiac output (CO), central venous pressure (CVP), pulmonary artery, pulmonary capillary wedge pressure, and all systemic arterial blood pressures, systolic (SAP), diastolic, (DAP) and mean (MAP) were measured. Systemic vascular resistance (SVR), pulmonary vascular resistance (PVR), cardiac index (CI), stroke volume (SV), oxygen extraction ratio (ER), and the alveolar to arterial oxygen gradient (PA-aO2) were calculated. In the echocardiographic phase, two-dimensional guided M-mode echocardiographic measurements were performed in the laterally recumbent dog. Indirect Doppler blood pressure determinations and ECG recordings were performed simultaneously with echocardiography measurements. The magnitude of change in cardiac indices was least with low dose RO. At most times, high dose RO produced significantly more alteration in cardiac indices. Increases in WS were noted in all treatment groups, although only minor increases were noted in T1 and T3. Overall, dramatic increases in WS occurred in the glycopyrrolate groups (T2, T4, T5). Romidifine produced cardiovascular effects consistent with other selective [alpha] 2-agonists. Cardiac performance, as measured with thermodilution and echocardiographic indices, was reduced in RO sedated dogs. The lower dosage of RO, 40 [mu]g/kg, produced less cardiovascular depression in both studies. (Abstract shortened by UMI.)

dogs, cardiopulmonary effects, Romifidine, glycopyrrolate treatment, echocardiography