Cardiovascular effects of a high dose of romifidine in propofol-anesthetized cats

Objective- To determine the hemodynamic effects of IM administration of romifidine hydrochloride in propofol-anesthetized cats. Animals-15 adult domestic shorthair cats. Procedure-Cats were randomly assigned to receive romifidine (0, 400, or 2,000 µg/kg, IM). Cats were anesthetized with propofol and mechanically ventilated with oxygen. The right jugular vein, left carotid artery, and right femoral artery and vein were surgically isolated and catheterized. Heart rate; duration of the PR, QRS, and QT intervals; mean pulmonary artery pressure; mean right atrial pressure; systolic, diastolic, and mean arterial pressures; left ventricular systolic pressure; left ventricular end-diastolic pressure; and cardiac output were monitored. Systemic vascular resistance, rate of change of left ventricular pressure, and rate pressure product were calculated. Arterial and venous blood samples were collected anaerobically for determination of pH and blood gas tensions (PO2 and PCO2). Results-Administration of romifidine at 400 and 2,000 µg/kg, IM, decreased heart rate, cardiac output, rate of change of left ventricular pressure, rate pressure product, and pH. Arterial and pulmonary artery pressures, left ventricular pressure, left ventricular end-diastolic pressure, and right atrial pressure increased and then gradually returned to baseline values. Arterial blood gas values did not change, whereas venous PCO2 increased and venous PO2 decreased. Significant differences between low and high dosages were rare, suggesting that the dosages investigated produced maximal hemodynamic effects. Conclusion and Clinical Relevance-Romifidine produces cardiovascular effects that are similar to those of other α2-agonists. High dosages of romifidine should be used with caution in cats with cardiovascular compromise.